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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BalanceSheetLocationDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Financial Position Location, Balance [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RestatementAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revision of Prior Period [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PlanNameAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Plan Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PlanNameAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Plan Name [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCurrentReportingStatus_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Current Reporting Status</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCurrentReportingStatus_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Current Reporting Status</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromWarrantExercises_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Warrant Exercises</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromWarrantExercises_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from exercise of warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromWarrantExercises_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Proceeds from exercise of pre-funded warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingExpensesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Expenses [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingExpensesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating expenses:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel2Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Significant Other Observable Inputs (Level 2)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel2Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Inputs, Level 2 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Commitments and Contingencies</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Commitments and Contingencies Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock, authorized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Shares Authorized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentFiscalPeriodFocus_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Fiscal Period Focus</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentFiscalPeriodFocus_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Document Fiscal Period Focus</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityShellCompany_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Shell Company</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityShellCompany_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Shell Company</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherAccruedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherAccruedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Accrued Liabilities, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_NoncashInvestingItemsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Supplemental disclosure of non-cash investing activities:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_NoncashInvestingItemsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Noncash Investing Items [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_NoncashInvestingItemsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Noncash investing items.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Cash and Cash Equivalents, at Carrying Value, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash and Cash Equivalent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash and cash equivalents</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseImpairmentLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease, Impairment Loss</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseImpairmentLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Impairment loss on ROU assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseImpairmentLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Impairment related to lease</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_LongTermIncentivePlan2025Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long Term Incentive Plan 2025 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_LongTermIncentivePlan2025Member_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Long Term Incentive Plan 2025 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_LongTermIncentivePlan2025Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Plan 2025</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock, Issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Shares, Issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Asset Class [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Statement [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCashNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Restricted cash</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCashNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restricted Cash, Noncurrent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Statement [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WarrantMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Warrant [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WarrantMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Warrant</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ClassOfWarrantOrRightExercisePriceOfWarrantsPaidAtClosingOfOffering_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Warrants exercise price per share paid at closing of offering</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ClassOfWarrantOrRightExercisePriceOfWarrantsPaidAtClosingOfOffering_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class Of Warrant Or Right Exercise Price Of Warrants Paid At Closing Of Offering</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ClassOfWarrantOrRightExercisePriceOfWarrantsPaidAtClosingOfOffering_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Class of warrant or right exercise price of warrants paid at closing of offering.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityFilerCategory_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Filer Category</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityFilerCategory_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Filer Category</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total liabilities and stockholders' equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities and Equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PayablesAndAccrualsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payables and Accruals [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainContingenciesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gain Contingencies [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainContingenciesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gain Contingencies [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentByTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Long-Lived Tangible Asset</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentByTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Lived Tangible Asset [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SeveranceCosts1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Severance Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SeveranceCosts1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Severance and related costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_LongTermIncentivePlan2015Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Plan 2015</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_LongTermIncentivePlan2015Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long Term Incentive Plan2015 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_LongTermIncentivePlan2015Member_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Long Term Incentive Plan 2015.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsFairValueDisclosure_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash and Cash Equivalents, Fair Value Disclosure</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsFairValueDisclosure_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Estimated Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesIssuedPricePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Public offering price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesIssuedPricePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Shares Issued, Price Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_RelatedPartyTransactionCollaborationAgreementInitialTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Related party transaction collaboration agreement, initial term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_RelatedPartyTransactionCollaborationAgreementInitialTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Related party transaction collaboration agreement, initial term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_RelatedPartyTransactionCollaborationAgreementInitialTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transaction Collaboration Agreement Initial Term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_RelatedPartyTransactionCollaborationAgreementInitialTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Related party transaction collaboration agreement, initial term.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Event [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeStockOptionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Stock Option [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxAuthorityAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Jurisdiction [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_FacilityAndAllOtherCostsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Facility and All Other Costs [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_FacilityAndAllOtherCostsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Facility and All Other Costs [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_FacilityAndAllOtherCostsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Facility and all other costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentsTextBlock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Error Corrections and Prior Period Adjustments [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PreFundedWarrantsToPurchase_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Pre-Funded Warrants To Purchase</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PreFundedWarrantsToPurchase_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Pre-funded warrants to purchase</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PreFundedWarrantsToPurchase_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Pre-funded warrants to purchase</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ScheduleOfSharesOfCommonStockReservedForFutureIssuanceTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Shares of Common Stock Reserved for Future Issuance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ScheduleOfSharesOfCommonStockReservedForFutureIssuanceTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Shares Of Common Stock Reserved For Future Issuance Table [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ScheduleOfSharesOfCommonStockReservedForFutureIssuanceTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Schedule of shares of common stock reserved for future issuance.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_AccruedResearchAndDevelopmentCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Research and development</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_AccruedResearchAndDevelopmentCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accrued Research And Development Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_AccruedResearchAndDevelopmentCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Accrued research and development, current.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapitalCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Additional paid-in capital</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapitalCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Additional Paid in Capital, Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapitalCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Additional paid-in capital</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_TwoThousandSeventeenAndTwoThousandTwentyFiveEquityIncentiveAwardPlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Seventeen And Two Thousand Twenty Five Equity Incentive Award Plan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_TwoThousandSeventeenAndTwoThousandTwentyFiveEquityIncentiveAwardPlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two Thousand Seventeen And Two Thousand Twenty Five Equity Incentive Award Plan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_TwoThousandSeventeenAndTwoThousandTwentyFiveEquityIncentiveAwardPlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2017 Plan and 2025 Plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_USGovernmentAgenciesDebtSecuritiesAndTreasuriesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">U.S. treasuries</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_USGovernmentAgenciesDebtSecuritiesAndTreasuriesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">U S Government Agencies Debt Securities And Treasuries [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_USGovernmentAgenciesDebtSecuritiesAndTreasuriesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">US government agencies debt securities and treasuries.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SignificantAccountingPoliciesTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Significant Accounting Policies</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Property Plant And Equipment [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Property, Plant and Equipment [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_AggregatePurchasePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Aggregate Purchase Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_AggregatePurchasePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Aggregate Purchase Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_AggregatePurchasePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Aggregate Purchase Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of stock options granted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Computation of Basic and Diluted Net Loss per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockCompensationPlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockCompensationPlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Potential shares issuable under the ESPP</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share, Basic</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Earnings Per Share, Basic, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net income (loss per share) - basic</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Basic EPS</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_TwoThousandSeventeenAndTwoThousandFifteenEquityIncentiveAwardPlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2017 Plan and 2015 Plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_TwoThousandSeventeenAndTwoThousandFifteenEquityIncentiveAwardPlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Seventeen And Two Thousand Fifteen Equity Incentive Award Plan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_TwoThousandSeventeenAndTwoThousandFifteenEquityIncentiveAwardPlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand seventeen and two thousand fifteen equity incentive award plan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAvailableForSaleSecuritiesReconciliationTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Available-for-Sale Securities Held</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAvailableForSaleSecuritiesReconciliationTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Available-for-Sale Securities Reconciliation [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total current liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_OptionsExercisableToPurchaseCommonStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Options Exercisable to Purchase Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_OptionsExercisableToPurchaseCommonStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Options Exercisable To Purchase Common Stock [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_OptionsExercisableToPurchaseCommonStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Options exercisable to purchase common stock.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Adjustments to reconcile net income to net cash used in operating activities:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PledgingPurposeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Pledging Purpose [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Effective Income Tax Rate Reconciliation [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ExistingLeaseObligations_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Existing lease obligations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ExistingLeaseObligations_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Existing lease obligations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ExistingLeaseObligations_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Existing Lease Obligations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stockholders' equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity, Attributable to Parent [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntitySmallBusiness_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Small Business</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntitySmallBusiness_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Small Business</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Retained Earnings (Accumulated Deficit), Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Accumulated deficit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accumulated deficit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Retained Earnings (Accumulated Deficit)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Accumulated deficit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PriorPeriodAdjustmentAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Prior Period Adjustment [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ResearchAndDevelopment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Research and Development</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ResearchAndDevelopment_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Research and Development</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ResearchAndDevelopment_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Research and development</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Stock [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SaleOfStockPricePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Sale of stock, price per share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SaleOfStockPricePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Sale of Stock, Price Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity-based Compensation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Organization, Consolidation and Presentation of Financial Statements [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_AmendmentFlag_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Amendment Flag</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_AmendmentFlag_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Amendment Flag</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongLivedAssetsHeldForSaleByAssetTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Lived Asset, Held-for-Sale, Type [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_CompensationAndBenefitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Compensation and Benefits [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_CompensationAndBenefitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Compensation and Benefits [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_CompensationAndBenefitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Compensation and benefits</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_RocheCollaborationAndOptionAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Roche Collaboration and Option Agreement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_RocheCollaborationAndOptionAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Roche Collaboration And Option Agreement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_RocheCollaborationAndOptionAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Roche collaboration and option agreement.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Warrants to purchase shares of common stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class of Warrant or Right, Number of Securities Called by Warrants or Rights</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesAndStockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Liabilities and Stockholders' Equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesAndStockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities and Equity [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressPostalZipCode_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, Postal Zip Code</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressPostalZipCode_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Address, Postal Zip Code</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net cash used in operating activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Provided by (Used in) Operating Activity, Including Discontinued Operation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOperatingLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating lease liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOperatingLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Operating Lease Liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common Stock $0.001 Par Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_TotalResearchAndDevelopmentExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Research and development</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_TotalResearchAndDevelopmentExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Total Research and Development Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_TotalResearchAndDevelopmentExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Total Research and Development Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_TotalResearchAndDevelopmentExpense_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Research and development</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_TotalResearchAndDevelopmentExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Research and development</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_RelatedPartyTransactionCollaborationAgreementInitialTermExtended_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Related Party Transaction Collaboration Agreement Initial Term Extended</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_RelatedPartyTransactionCollaborationAgreementInitialTermExtended_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transaction Collaboration Agreement Initial Term Extended</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_RelatedPartyTransactionCollaborationAgreementInitialTermExtended_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Related Party Transaction Collaboration Agreement Initial Term Extended</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted average exercise price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Grants in Period, Weighted Average Exercise Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Ending Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Less accumulated depreciation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_AmortizedCostFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Amortized Cost Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_AmortizedCostFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Amortized Cost Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_AmortizedCostFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Amortized Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Available-for-sale Securities [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressAddressLine1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, Address Line One</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressAddressLine1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Address, Address Line One</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueByFairValueHierarchyLevelAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Hierarchy and NAV</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueByFairValueHierarchyLevelAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Hierarchy and NAV [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PreWarrantAtAPublicOfferingPrice_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Pre-funded warrant public offering price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PreWarrantAtAPublicOfferingPrice_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Pre-Warrant at a public offering price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PreWarrantAtAPublicOfferingPrice_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Pre-Warrant at a public offering price</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BalanceSheetLocationAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Financial Position Location, Balance [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Type [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investment Type</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseRightOfUseAsset_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Right of use asset - operating lease</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseRightOfUseAsset_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease, Right-of-Use Asset</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Debt Securities, Available-for-Sale, Unrealized Loss Position, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Aggregate fair value of securities in unrealized loss position</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale, Unrealized Loss Position</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquireAvailableForSaleSecuritiesDebt_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Purchases of marketable securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquireAvailableForSaleSecuritiesDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments to Acquire Debt Securities, Available-for-Sale</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfWarrantOrRightAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Class of Warrant or Right</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfWarrantOrRightAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class of Warrant or Right [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentType_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Type</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentType_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Document Type</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxesPaidNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash paid for income taxes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxesPaidNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Taxes Paid, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxesPaidNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Income Taxes Paid, Net, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TypeOfArrangementAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Collaborative Arrangement and Arrangement Other than Collaborative</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TypeOfArrangementAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Collaborative Arrangement and Arrangement Other than Collaborative [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ArrangementsAndNonarrangementTransactionsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Collaborative Arrangement and Arrangement Other than Collaborative</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ArrangementsAndNonarrangementTransactionsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Collaborative Arrangement and Arrangement Other than Collaborative [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCentralIndexKey_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Central Index Key</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCentralIndexKey_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Central Index Key</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments, Debt and Equity Securities [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_AvailableForSaleSecuritiesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Available-for-Sale Securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_AvailableForSaleSecuritiesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Available For Sale Securities Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_AvailableForSaleSecuritiesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Available for sale securities disclosure.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net decrease in cash, cash equivalents and restricted cash</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Event Type [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAdjustmentOfWarrants_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Change in fair value of purchase warrant liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAdjustmentOfWarrants_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Adjustment of Warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAdjustmentOfWarrants_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Adjustment of Warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAdjustmentOfWarrants_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Change in fair value of purchase warrant liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Anti-dilutive potential common shares excluded from the EPS computation above</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OptionIndexedToIssuersEquityEquityAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Option Indexed to Issuer's Equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OptionIndexedToIssuersEquityEquityAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Option Indexed to Issuer's Equity [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ShareBasedCompensationArrangementBySharesBasedPaymentAwardFairValueAssumptionsStrikePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Strike price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ShareBasedCompensationArrangementBySharesBasedPaymentAwardFairValueAssumptionsStrikePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Share Based Compensation Arrangement By Shares Based Payment Award Fair Value Assumptions Strike Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ShareBasedCompensationArrangementBySharesBasedPaymentAwardFairValueAssumptionsStrikePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Shares Based Payment Award Fair Value Assumptions Strike Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock, par value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Par or Stated Value Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PublicOfferingLessExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Public offering less exercise price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PublicOfferingLessExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Public Offering Less Exercise Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PublicOfferingLessExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Public Offering Less Exercise Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Amortized cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale, Amortized Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Debt Securities, Available-for-Sale, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnTerminationOfLease_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Gain on lease termination</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnTerminationOfLease_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gain (Loss) on Termination of Lease</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnTerminationOfLease_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gain on lease termination</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnTerminationOfLease_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Gain on lease termination</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Exercise of options, shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherPrepaidExpenseCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Other prepaid expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherPrepaidExpenseCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Prepaid Expense, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherPrepaidExpenseCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other Prepaid Expense, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccruedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total accrued expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccruedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccruedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accrued Liabilities, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardGross_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of restricted stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardGross_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period, Value, Restricted Stock Award, Gross</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PrepaidExpensesAndOtherCurrentAssetsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Prepaid Expenses and Other Current Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PrepaidExpensesAndOtherCurrentAssetsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Prepaid Expenses And Other Current Assets [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PrepaidExpensesAndOtherCurrentAssetsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Prepaid expenses and other current assets.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CurrentFiscalYearEndDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Current Fiscal Year End Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CurrentFiscalYearEndDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Current Fiscal Year End Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_FormerHeadquarterMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Former Headquarter Member</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_FormerHeadquarterMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Former Headquarter [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_FormerHeadquarterMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Former Headquarter [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_TwoThousandTwentyThreeInducementPlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Three Inducement Plan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_TwoThousandTwentyThreeInducementPlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two Thousand Twenty Three Inducement Plan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentQuarterlyReport_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Quarterly Report</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentQuarterlyReport_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Document Quarterly Report</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressStateOrProvince_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, State or Province</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressStateOrProvince_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Address, State or Province</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Stock, Shares Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Preferred Stock, Shares Outstanding, Ending Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Preferred Stock, Shares Outstanding, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ComprehensiveIncomeNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Comprehensive Income (Loss), Net of Tax, Attributable to Parent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ComprehensiveIncomeNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Comprehensive income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gross unrealized gains</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total Shares of Common Stock Reserved for Future Issuance</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfWarrantOrRightDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Class of Warrant or Right</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfWarrantOrRightDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class of Warrant or Right [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Equity-based Compensation Expenses</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsPayableAccruedLiabilitiesAndOtherLiabilitiesDisclosureCurrentTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued Expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsPayableAccruedLiabilitiesAndOtherLiabilitiesDisclosureCurrentTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accounts Payable, Accrued Liabilities, and Other Liabilities Disclosure, Current [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CollaborativeArrangementDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Collaboration Agreements</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CollaborativeArrangementDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Collaborative Arrangement Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromSaleAndMaturityOfMarketableSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from maturity of marketable securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromSaleAndMaturityOfMarketableSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Sale and Maturity of Marketable Securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Subsequent Event [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Event [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Property, Plant and Equipment [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Increase in number of shares available for issuance (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Additional Shares Authorized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherAssetsNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherAssetsNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Assets, Noncurrent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Short-term marketable securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Antidilutive Securities [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_Scheduleoffairvalueassetsandliabilitiesmeasuredgrossunrealizedgainsandlossestabletextblock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Fair Value Assets and Liabilities Measured Gross Unrealized Gains and Losses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_Scheduleoffairvalueassetsandliabilitiesmeasuredgrossunrealizedgainsandlossestabletextblock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Fair Value Assets and Liabilities Measured Gross Unrealized Gains and Losses [TableText Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_Scheduleoffairvalueassetsandliabilitiesmeasuredgrossunrealizedgainsandlossestabletextblock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Schedule of Fair Value Assets and Liabilities Measured Gross Unrealized Gains and Losses [TableText Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accumulated Other Comprehensive Income (Loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">AOCI Attributable to Parent [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_DecreaseInRightOfUseAssetAndOperatingLeaseLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Decrease In Right-Of-Use Asset And Operating Lease Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_DecreaseInRightOfUseAssetAndOperatingLeaseLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Decrease in right-of-use asset and operating lease liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_DecreaseInRightOfUseAssetAndOperatingLeaseLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Decrease in right-of-use asset and operating lease liabilities due to lease termination</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockCommonShares_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Balance (in Shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockCommonShares_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Balance (in Shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockCommonShares_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Treasury Stock, Common, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockCommonShares_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedPeriodStartLabel">Balance (in Shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ScheduleOfPrepaidExpensesAndOtherCurrentAssetsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Prepaid Expenses And Other Current Assets Table [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ScheduleOfPrepaidExpensesAndOtherCurrentAssetsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Schedule of prepaid expenses and other current assets.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ScheduleOfPrepaidExpensesAndOtherCurrentAssetsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Prepaid Expenses and Other Current Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash and Cash Equivalents</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash and Cash Equivalents [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_TotalTerminationPayment_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total termination payment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_TotalTerminationPayment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Total Termination Payment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_TotalTerminationPayment_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Total Termination Payment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MinimumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Minimum [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MinimumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Minimum</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted average grant date fair value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinancialInstrumentAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Financial Instrument</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinancialInstrumentAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Financial Instrument [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsCurrentAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Current assets:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsCurrentAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Assets, Current [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PurchaseWarrantLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Purchase Warrant Liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PurchaseWarrantLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Purchase Warrant Liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PurchaseWarrantLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Purchase warrant liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PrepaidResearchAndDevelopmentNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Prepaid research and development, net of current portion</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PrepaidResearchAndDevelopmentNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Prepaid Research And Development Noncurrent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PrepaidResearchAndDevelopmentNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Prepaid research and development noncurrent.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel3Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Significant Unobservable Inputs (Level 3)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel3Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Inputs, Level 3 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesFairValueDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities, Fair Value Disclosure [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Segment Information</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Segment Reporting [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Company's Classified Assets Measured at Fair Value on Recurring Basis</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ReductionInCarryingAmountOfOperatingLeaseRightOfUseAsset_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Reduction in carrying amount of operating lease right of use asset</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ReductionInCarryingAmountOfOperatingLeaseRightOfUseAsset_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Reduction In Carrying Amount Of Operating Lease Right Of Use Asset</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ReductionInCarryingAmountOfOperatingLeaseRightOfUseAsset_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Reduction in carrying amount of operating lease right-of-use asset.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesCurrentAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Current liabilities:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesCurrentAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities, Current [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringAndRelatedActivitiesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restructuring and Related Activities Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringAndRelatedActivitiesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Restructuring and Other Charges</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transactions [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Balance (in Shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Balance (in Shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Shares, Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidExpenseNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Prepaid Expense, Noncurrent, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidExpenseNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Non-current pre-paid research and development</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidExpenseNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Prepaid Expense, Noncurrent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_October2023FinancingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">October 2023 Financing [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_October2023FinancingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">October 2023 Financing [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_October2023FinancingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">October 2023 Financing</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingencies_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Commitments and Contingencies</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingencies_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Commitments and contingencies (Note 10)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GeneralAndAdministrativeExpenseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">General and Administrative Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GeneralAndAdministrativeExpenseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">General and Administrative Expense [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Error Corrections and Prior Period Adjustments Restatement [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityReverseStockSplit_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Reverse Stock Split , Description</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityReverseStockSplit_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stockholders' Equity, Reverse Stock Split</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityReverseStockSplit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Reverse Stock Split, Decsription</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ComputerAndOfficeEquipmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Computer and Office Equipment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ComputerAndOfficeEquipmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Computer And Office Equipment [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ComputerAndOfficeEquipmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Computer and office equipment.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Finance lease obligations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Finance Lease, Liability, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesNoncurrentAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Long-term liabilities:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesNoncurrentAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities, Noncurrent [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TextBlockAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Text Block [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProfitLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProfitLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Income (Loss), Including Portion Attributable to Noncontrolling Interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProfitLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ProceedsFromEmployeeStockPurchasesAndExerciseOfStockOptions_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from employee stock purchases and exercise of stock options</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ProceedsFromEmployeeStockPurchasesAndExerciseOfStockOptions_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds From Employee Stock Purchases And Exercise Of Stock Options</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ProceedsFromEmployeeStockPurchasesAndExerciseOfStockOptions_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Proceeds from employee stock purchases and exercise of stock options.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Weighted Average Number of Shares Outstanding, Basic</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Basic weighted-average common shares outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted-average common shares - basic</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Weighted Average Number of Shares Outstanding, Basic, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_CurrentPrePaidResearchAndDevelopment_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Current Pre-Paid Research and Development</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_CurrentPrePaidResearchAndDevelopment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Current Pre Paid Research And Development</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_CurrentPrePaidResearchAndDevelopment_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Current Pre-Paid Research and Development.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentInformationLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Document Information [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_CommonStockAtAnExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock at an exercise price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_CommonStockAtAnExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock At An Exercise Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_CommonStockAtAnExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Common Stock At An Exercise Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_AccruedRestructuringCharges_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued restructuring charges</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_AccruedRestructuringCharges_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Accrued restructuring charges.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_AccruedRestructuringCharges_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accrued restructuring charges.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Long-Lived Tangible Asset</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Lived Tangible Asset [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ShareBasedCompensationArrangementBySharebasedPaymentawardFairValueAssumptionsStockPrice_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Share Based Compensation Arrangement By ShareBased PaymentAward Fair Value Assumptions Stock Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ShareBasedCompensationArrangementBySharebasedPaymentawardFairValueAssumptionsStockPrice_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By ShareBased PaymentAward Fair Value Assumptions Stock Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ShareBasedCompensationArrangementBySharebasedPaymentawardFairValueAssumptionsStockPrice_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesReverseStockSplits_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period, Shares, Reverse Stock Splits</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesReverseStockSplits_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Reverse Split: fractional share adjustment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Subsequent Events</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Events [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionsDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Related-Party Transactions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionsDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transactions Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">APIC, Share-Based Payment Arrangement, Increase for Cost Recognition, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity-based compensation expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">APIC, Share-Based Payment Arrangement, Increase for Cost Recognition</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_NetIncomePerShareTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Income Per Share [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_NetIncomePerShareTable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Net Income Per Share [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total stockholders' equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity, Attributable to Parent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total stockholders' equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockParOrStatedValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Preferred Stock Par Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockParOrStatedValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Stock, Par or Stated Value Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BasisOfAccountingPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Basis of Presentation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BasisOfAccountingPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Basis of Accounting, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PrepaidResearchAndDevelopmentExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Prepaid research and development expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PrepaidResearchAndDevelopmentExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Prepaid Research And Development Expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PrepaidResearchAndDevelopmentExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Prepaid research and development expenses.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementOfStockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Stockholders' Equity [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_NonCurrentPrePaidResearchAndDevelopment_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Non Current Pre-Paid Research and Development</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_NonCurrentPrePaidResearchAndDevelopment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Non Current Pre Paid Research And Development</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_NonCurrentPrePaidResearchAndDevelopment_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Non Current Pre-Paid Research and Development</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SeriesAPreferredStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Series A Preferred Stock [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SeriesAPreferredStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Series A Preferred Stock [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockCommonMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Treasury Stock, Common [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockCommonMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Treasury Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringReserveTranslationAdjustment_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Restructuring Additional Gain</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringReserveTranslationAdjustment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restructuring Reserve, Foreign Currency Translation Gain (Loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringReserveTranslationAdjustment_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Restructuring including legal and consulting fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeaseholdImprovementsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Leasehold Improvements</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeaseholdImprovementsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Leasehold Improvements [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressAddressLine2_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, Address Line Two</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressAddressLine2_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Address, Address Line Two</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueDisclosuresTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value of Financial Instruments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueDisclosuresTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Disclosures [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisclosureOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Equity-based Compensation Expenses by Award Type</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisclosureOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Disclosure of Share-Based Compensation Arrangements by Share-Based Payment Award [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ReverseStockSplitApprovalDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Reverse Stock Split Approval Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ReverseStockSplitApprovalDate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Reverse Stock Split Approval Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAccruedLiabilitiesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Accrued Expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAccruedLiabilitiesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Accrued Liabilities [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherAssetsCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Assets, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherAssetsCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other current assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_LabEquipmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Lab Equipment [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_LabEquipmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lab Equipment [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceAndAdditionalDisclosuresAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price And Additional Disclosures [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceAndAdditionalDisclosuresAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Share-based compensation arrangement by share-based payment award, options outstanding, weighted average exercise price, and additional disclosures.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_AgreedToPayToRenovateAndUpgradeCleanroomSpace_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Agreed to pay to renovate and upgrade cleanroom space</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_AgreedToPayToRenovateAndUpgradeCleanroomSpace_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Agreed To Pay To Renovate And Upgrade Cleanroom Space</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_AgreedToPayToRenovateAndUpgradeCleanroomSpace_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Agreed to pay to renovate and upgrade cleanroom space.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PlanNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Plan Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PlanNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Plan Name [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOtherOperatingAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Increase (Decrease) in Other Operating Assets, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOtherOperatingAssets_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Other assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOtherOperatingAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Other Operating Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ImpairmentForInProcessResearchAndDevelopment_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Impairment for in-process research and development</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ImpairmentForInProcessResearchAndDevelopment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Impairment for in-process research and development</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_Cashequivalentsaccumulatedgrossunrealizedloss_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">CashEquivalentsAccumulatedGrossUnrealizedLoss</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_Cashequivalentsaccumulatedgrossunrealizedloss_lbl" xlink:role="http://www.xbrl.org/2003/role/label">CashEquivalentsAccumulatedGrossUnrealizedLoss</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_Cashequivalentsaccumulatedgrossunrealizedloss_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gross Unrealized Loss</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Treasury Stock, Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Treasury Stock, Value, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockValue_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Treasury stock, at cost (279,792 shares at March 31, 2026 and at December 31, 2025)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringPlanAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restructuring Plan [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Related Party</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related and Nonrelated Parties [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_NonRule10B51ArrModifiedFlag_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Non Rule 10b51 Arr Modified Flag</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_NonRule10B51ArrModifiedFlag_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Non Rule 10b51 Arr Modified Flag</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressCityOrTown_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, City or Town</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressCityOrTown_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Address, City or Town</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_SecurityExchangeName_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Security Exchange Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_SecurityExchangeName_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Security Exchange Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentGross_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Property, Plant and Equipment, Gross, Ending Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentGross_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Property, Plant and Equipment, Gross, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentGross_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Property, Plant and Equipment, Gross, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentGross_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Property and equipment, gross</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentGross_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Property, Plant and Equipment, Gross</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ShareRepurchaseAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Repurchase [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ShareRepurchaseAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Share Repurchase [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Loss before income taxes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Loss before income taxes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_RestructuringChargesExpenseAccelerationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Restructuring Charges Expense Acceleration [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_RestructuringChargesExpenseAccelerationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restructuring Charges Expense Acceleration [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_RestructuringChargesExpenseAccelerationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Restructuring charges: expense acceleration</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PledgingPurposeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Pledging Purpose [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AntidilutiveSecuritiesNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Antidilutive Securities, Name [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RangeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statistical Measurement [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class of Warrant or Right, Exercise Price of Warrants or Rights</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Warrants exercise price per share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Assets, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total current assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AllocatedShareBasedCompensationExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity-based compensation expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AllocatedShareBasedCompensationExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement, Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NoncashOrPartNoncashAcquisitionFixedAssetsAcquired1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Property and equipment sales included in other current assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NoncashOrPartNoncashAcquisitionFixedAssetsAcquired1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Noncash or Part Noncash Acquisition, Fixed Assets Acquired</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_FederalAndStateDeferredTaxMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Federal and State Deferred Tax [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_FederalAndStateDeferredTaxMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Federal and state deferred tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_FederalAndStateDeferredTaxMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Federal and State Deferred Tax [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentPeriodEndDate_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Document Period End Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentPeriodEndDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Document Period End Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Hierarchy and NAV</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Hierarchy and NAV [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnSaleOfPropertyPlantEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Gain (Loss) on Disposition of Property Plant Equipment, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnSaleOfPropertyPlantEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gains on equipment sales</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnSaleOfPropertyPlantEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gain (Loss) on Disposition of Property Plant Equipment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementOfFinancialPositionAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Financial Position [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisposalGroupNotDiscontinuedOperationGainLossOnDisposal_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">(Gain)/loss on disposal of property and equipment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisposalGroupNotDiscontinuedOperationGainLossOnDisposal_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisposalGroupNotDiscontinuedOperationGainLossOnDisposal_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Gain on disposal of property and equipment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Antidilutive Security, Excluded EPS Calculation [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementClassOfStockAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class of Stock [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionNumberOfPositions_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of investments in unrealized loss position</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionNumberOfPositions_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale, Unrealized Loss Position, Number of Positions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Financial Instruments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Financial Instruments [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DilutiveSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Effect of dilutive securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DilutiveSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dilutive Securities, Effect on Basic Earnings Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DilutiveSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Dilutive Securities, Effect on Basic Earnings Per Share, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Restricted Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restricted Stock [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Restricted Stock Awards [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerNumberOfPositions_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of investments in unrealized loss position, more than twelve months</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerNumberOfPositions_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Weighted Average Number of Shares Outstanding, Diluted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Weighted Average Number of Shares Outstanding, Diluted, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Diluted weighted-average common shares outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityFileNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity File Number</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityFileNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Securities Act File Number</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Unrealized gain (loss) on securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, after Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Net unrealized loss on marketable securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_Rule10B51ArrModifiedFlag_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Rule 10b51 Arr Modified Flag</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_Rule10B51ArrModifiedFlag_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Rule 10b51 Arr Modified Flag</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CoverAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cover [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_RestructuringIncludingLegalFees_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Restructuring including legal fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_RestructuringIncludingLegalFees_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restructuring including legal fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_RestructuringIncludingLegalFees_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Restructuring including legal fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accounts payable and accrued expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Increase (Decrease) in Accounts Payable and Accrued Liabilities, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Accounts Payable and Accrued Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeNonoperating_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Investment Income, Nonoperating, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeNonoperating_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest and investment income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeNonoperating_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Income, Nonoperating</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidExpenseAndOtherAssetsCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total prepaid expenses and other current assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidExpenseAndOtherAssetsCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Prepaid expenses and other current assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidExpenseAndOtherAssetsCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Prepaid Expense and Other Assets, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentTypeCategorizationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentTypeCategorizationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_CommissionsAndOfferingExpensesPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Commissions and Offering Expenses Payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_CommissionsAndOfferingExpensesPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Commissions and Offering Expenses Payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_CommissionsAndOfferingExpensesPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Commissions and Offering Expenses Payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NumberOfOperatingSegments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of operating segment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NumberOfOperatingSegments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Number of Operating Segments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SaleOfStockNameOfTransactionDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Sale of Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SaleOfStockNameOfTransactionDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Sale of Stock [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Segment Reporting Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Segment Information</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GeneralAndAdministrativeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">General and Administrative Expense, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GeneralAndAdministrativeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">General and administrative</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GeneralAndAdministrativeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">General and Administrative Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_NoncashFinancingItemsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Supplemental disclosure of non-cash financing activities:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_NoncashFinancingItemsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Noncash Financing Items [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_NoncashFinancingItemsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Noncash financing items.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PrepaymentToRelatedPartyForCollaborationAgreement_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Prepayment to related party for collaboration agreement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PrepaymentToRelatedPartyForCollaborationAgreement_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Prepayment to related party for collaboration agreement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PrepaymentToRelatedPartyForCollaborationAgreement_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Prepayment To Related Party For Collaboration Agreement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PrepaymentToRelatedPartyForCollaborationAgreement_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Prepayment to related party for collaboration agreement.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Event [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalWarrantIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Adjustments to Additional Paid in Capital, Warrant Issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalWarrantIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">The purchase warrants were recorded as a liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_RepurchaseOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Repurchase of common stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_RepurchaseOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Repurchase of common stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_RepurchaseOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Repurchase of common stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringCharges_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Restructuring Charges, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringCharges_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restructuring Charges</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringCharges_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Restructuring and other charges</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringCharges_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Restructuring charge</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_FairValueAssetMeasuredOnRecurringBasisTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Asset Measured On Recurring Basis [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_FairValueAssetMeasuredOnRecurringBasisTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Asset Measured On Recurring Basis [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_FairValueAssetMeasuredOnRecurringBasisTable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Fair Value Asset Measured On Recurring Basis [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Recently Issued Accounting Pronouncements</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">New Accounting Pronouncements, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiabilityCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Current deferred revenue</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiabilityCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred revenue</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiabilityCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Contract with Customer, Liability, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnDispositionOfAssets1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gain on disposal</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnDispositionOfAssets1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gain (Loss) on Disposition of Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnDispositionOfAssets1_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Gain (Loss) on Disposition of Assets, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongLivedAssetsHeldForSaleNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Lived Assets Held-for-Sale, Name [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Common Stock, Shares, Outstanding, Ending Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Common Stock, Shares, Outstanding, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock, outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Shares, Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiabilityCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lease liability - operating lease</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiabilityCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease, Liability, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentTransitionReport_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Transition Report</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentTransitionReport_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Document Transition Report</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total operating expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ResearchAndDevelopmentExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Research and Development Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ResearchAndDevelopmentExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Research and Development Expense, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ResearchAndDevelopmentExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Research and development</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetImpairmentCharges_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Impairment Charge</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetImpairmentCharges_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Asset Impairment Charges</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetImpairmentCharges_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Asset Impairment Charges, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementOfCashFlowsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Cash Flows [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ScheduleOfOptionPricingModelAtIssuanceTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Schedule Of Option Pricing Model At Issuance Table Text Block</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ScheduleOfOptionPricingModelAtIssuanceTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Option Pricing Model At Issuance Table Text Block</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ScheduleOfOptionPricingModelAtIssuanceTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Assumptions Used in Determining Fair Value of Warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period, Value, New Issues</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from issuance of common stock in connection with at-the-market offering, net of issuance costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsFairValueDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Assets, Fair Value Disclosure [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsFairValueDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Assets:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityNoteDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stockholders' Equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityNoteDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net Income per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetIncomeLoss_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Net loss</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetIncomeLoss_lbl" xlink:role="http://www.xbrl.org/2009/role/netLabel">Net Income(Loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetIncomeLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Net income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetIncomeLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_CompensationIncludedInRestructuringCharges_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Compensation included in restructuring charges</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_CompensationIncludedInRestructuringCharges_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Compensation included in restructuring charges</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_CompensationIncludedInRestructuringCharges_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Compensation included in restructuring charges</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PreFundedWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Common Stock Issuable Under Pre-Funded Warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PreFundedWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Pre-Funded Warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PreFundedWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Pre Funded Warrants [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PreFundedWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Pre-Funded Warrants.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Expected Dividend Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividend yield</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Assets [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Risk Free Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted-average, risk free interest rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConstructionInProgressMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Construction in Progress</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConstructionInProgressMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Construction in Progress [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Prepaid expenses and other current assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Prepaid Expense and Other Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringAndRelatedActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restructuring and Related Activities [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentFiscalYearFocus_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Fiscal Year Focus</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentFiscalYearFocus_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Document Fiscal Year Focus</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_GinkgoBioworksIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Ginkgo Collaboration</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_GinkgoBioworksIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Ginkgo Bioworks Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_GinkgoBioworksIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Ginkgo Bioworks, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_GinkgoBioworksIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock issuable under Ginkgo pre-funded warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash flows from investing activities:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsPayableCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Accounts Payable, Current, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsPayableCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accounts payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsPayableCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accounts Payable, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ResearchAndDevelopmentExpenseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Research and Development Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ResearchAndDevelopmentExpenseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Research and Development Expense [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredRevenue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred revenue balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredRevenue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Revenue</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredRevenue_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Deferred Revenue, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ReductionInWorkforce_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Reduction in WorkForce</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ReductionInWorkforce_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Reduction in WorkForce</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ReductionInWorkforce_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Reduction in WorkForce</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringCostAndReserveLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restructuring Cost and Reserve [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RestatementDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revision of Prior Period [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueDisclosuresAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Disclosures [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Commitments and Contingencies Disclosure [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_IncreaseDecreaseInPrepaidResearchAndDevelopmentNetOfCurrentPortion_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Prepaid research and development, net of current portion</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_IncreaseDecreaseInPrepaidResearchAndDevelopmentNetOfCurrentPortion_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease In Prepaid Research And Development Net Of Current Portion</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_IncreaseDecreaseInPrepaidResearchAndDevelopmentNetOfCurrentPortion_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Increase (decrease) in prepaid research and development net of current portion.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateReconciliationLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Effective Income Tax Rate Reconciliation [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisclosureOfCompensationRelatedCostsSharebasedPaymentsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsFairValueDisclosure_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsFairValueDisclosure_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Assets, Fair Value Disclosure</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PurchaseWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Purchase Warrants [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PurchaseWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Purchase Warrants [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PurchaseWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Purchase warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsidiarySaleOfStockAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Sale of Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsidiarySaleOfStockAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Sale of Stock [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Revenues_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Revenues, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Revenues_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Recognition of revenue</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Revenues_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revenue</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Revenues_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revenues</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net cash provided by investing activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Provided by (Used in) Investing Activity, Including Discontinued Operation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_Security12bTitle_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Title of 12(b) Security</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_Security12bTitle_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Title of 12(b) Security</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Segment Reporting Information, by Segment [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_CommonStockAndWarrantsPurchase_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock and warrants purchase</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_CommonStockAndWarrantsPurchase_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock And warrants Purchase</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_CommonStockAndWarrantsPurchase_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Common Stock And warrants Purchase</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainContingenciesTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gain Contingencies [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainContingenciesTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gain Contingencies [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MoneyMarketFundsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Money market funds</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MoneyMarketFundsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Money Market Funds [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Related Party</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related and Nonrelated Parties [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Taxes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Collaborative Arrangements And Noncollaborative Arrangement Transactions [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Collaborative Arrangement and Arrangement Other than Collaborative [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_OtherThanTemporaryImpairmentLossesInvestmentsNumberDebtSecuritiesAvailableForSale_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of securities with other than temporary impairment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_OtherThanTemporaryImpairmentLossesInvestmentsNumberDebtSecuritiesAvailableForSale_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Than Temporary Impairment Losses Investments Number Debt Securities Available For Sale</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_OtherThanTemporaryImpairmentLossesInvestmentsNumberDebtSecuritiesAvailableForSale_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Other than temporary impairment losses investments number debt securities available for sale.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_WarrantsExercised_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Warrants exercised</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_WarrantsExercised_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Warrants Exercised</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_WarrantsExercised_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Warrants exercised.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfWarrantOrRightReasonForIssuingToNonemployees_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Pre fund warrant purchase description</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfWarrantOrRightReasonForIssuingToNonemployees_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Warrant or Right, Reason for Issuance, Description</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentInformationTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Document Information [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringPlanDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restructuring Plan [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_LegalEntityAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Legal Entity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_LegalEntityAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Legal Entity [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Changes in operating assets and liabilities:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Increase (Decrease) in Operating Capital [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Property and Equipment, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Property, Plant and Equipment [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Disclosure [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrecognizedTaxBenefits_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Unrecognized tax benefits</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrecognizedTaxBenefits_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Unrecognized Tax Benefits</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrecognizedTaxBenefits_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Unrecognized Tax Benefits, Ending Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrecognizedTaxBenefits_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Unrecognized Tax Benefits, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapitalMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Additional Paid-in Capital</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapitalMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Additional Paid-in Capital [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementFrequencyDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Measurement Frequency</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementFrequencyDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Measurement Frequency [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementLocationAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Statement Location</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementLocationAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Income Location, Balance [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PrepaidResearchAndDevelopmentCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Prepaid research and development</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PrepaidResearchAndDevelopmentCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Prepaid Research And Development Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PrepaidResearchAndDevelopmentCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Prepaid research and development, current.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_PrepaidResearchAndDevelopmentCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Prepaid Research And Development Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_TradingSymbol_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Trading Symbol</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_TradingSymbol_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Trading Symbol</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Property and Equipment, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Property, Plant and Equipment Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Related Party Transactions By Related Party [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transaction [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Event Type [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RestatementAdjustmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revision of Prior Period, Adjustment [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RestatementAdjustmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">RestatementAdjustmentMember</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeRelatedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Employee-related Liabilities, Current, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeRelatedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Payroll related</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeRelatedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Employee-related Liabilities, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash flows from financing activities:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Expected Term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Expected Term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementsRecurringMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Recurring</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementsRecurringMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Recurring [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentAssetsHeldForSaleDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Property, Plant and Equipment Assets Held-for-Sale Disclosure [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementEquityComponentsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accumulated Deficit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementEquityComponentsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Components [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NonoperatingIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Nonoperating Income (Expense)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NonoperatingIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other income (expense), net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NonoperatingIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total other income, net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityComponentDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity Component</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityComponentDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Component [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueByAssetClassAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Asset Class [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongLivedAssetsHeldForSaleLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Lived Assets Held-for-Sale [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ProceedsFromIssuanceOfCommonStockAndPreFundedWarrants_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from issuance of common stock and pre-funded warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ProceedsFromIssuanceOfCommonStockAndPreFundedWarrants_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds From Issuance Of Common Stock And Pre Funded Warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ProceedsFromIssuanceOfCommonStockAndPreFundedWarrants_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Proceeds from issuance of common stock and pre funded warrants.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeaseholdImprovementsGross_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lease Improvements</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeaseholdImprovementsGross_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Leasehold Improvements, Gross</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_CommonStockAndWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Common Stock And Warrants [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_CommonStockAndWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock And Warrants [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_CommonStockAndWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common Stock And Warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidInsurance_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Prepaid Insurance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidInsurance_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Prepaid insurance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_AggregatePurchase_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Aggregate Purchase</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_AggregatePurchase_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Aggregate Purchase</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_AggregatePurchase_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Aggregate Purchase</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_EstimatedProjectCostForAccessPersonalSupportAndOtherServices_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Estimated project cost for access personal support and other services</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_EstimatedProjectCostForAccessPersonalSupportAndOtherServices_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Estimated Project Cost For Access Personal Support And Other Services</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_EstimatedProjectCostForAccessPersonalSupportAndOtherServices_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Estimated project cost For access personal support and other services.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock under employee stock purchase plan, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period, Shares, Employee Stock Purchase Plans</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementOfIncomeAndComprehensiveIncomeAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Comprehensive Income [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MaximumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Maximum [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MaximumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maximum</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesFairValueDisclosure_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities, Fair Value Disclosure</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesFairValueDisclosure_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RangeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statistical Measurement [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidExpenseCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Prepaid Expense, Current, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidExpenseCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Current pre-paid research and development</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidExpenseCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Prepaid Expense, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Value, Issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">250,000,000 shares authorized as of March 31, 2026 and December 31, 2025; 11,978,711 shares issued and 11,698,919 shares outstanding as of March 31, 2026 and 11,978,711 shares issued and 11,698,919 shares outstanding as of December 31, 2025</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeasePrincipalPayments_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Payments on finance lease obligations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeasePrincipalPayments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Finance Lease, Principal Payments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_AtTheMarketOfferingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">At-the-market Offering</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_AtTheMarketOfferingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">At The Market Offering [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_AtTheMarketOfferingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">At-the-market offering,</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ResearchAndMilestonePayment_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Research and milestone payment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ResearchAndMilestonePayment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Research And Milestone Payment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ResearchAndMilestonePayment_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Research And Milestone Payment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConsolidationPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Principles of Consolidation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConsolidationPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Consolidation, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_CurrentLiabilitiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Current Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_CurrentLiabilitiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Current Liabilities [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_CurrentLiabilitiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Current liabilities.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquipmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Laboratory Equipment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquipmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equipment [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ComprehensiveIncomeNetOfTaxAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ComprehensiveIncomeNetOfTaxAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Comprehensive income:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ShareRepurchaseTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Share Repurchase</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ShareRepurchaseTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Repurchase [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ShareRepurchaseTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Share Repurchase [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisclosureOfLongLivedAssetsHeldForSaleTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Disclosure of Long-Lived Assets Held-for-Sale [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisclosureOfLongLivedAssetsHeldForSaleTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Assets Held for Sale</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Expected Volatility Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Expected volatility</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Related Party Transaction [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transaction [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">ESPP</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Employee Stock Purchase Plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Employee Stock [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityRegistrantName_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Entity Registrant Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityRegistrantName_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Registrant Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Gross unrealized losses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNonoperatingIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Other Nonoperating Income (Expense), Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNonoperatingIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Nonoperating Income (Expense)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNonoperatingIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other income (expense)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_AssetsAcquiredUnderOperatingLeaseObligation_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Assets acquired under operating lease obligation.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_AssetsAcquiredUnderOperatingLeaseObligation_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Assets Acquired Under Operating Lease Obligation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_AssetsAcquiredUnderOperatingLeaseObligation_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Assets acquired under operating lease obligation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Events [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_AzzurGroupLimitedLiabilityCompanyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Azzur</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_AzzurGroupLimitedLiabilityCompanyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Azzur Group Limited Liability Company [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_AzzurGroupLimitedLiabilityCompanyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Azzur Group Limited Liability Company.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income tax expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Income tax expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Expense (Benefit)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Income Tax Expense (Benefit), Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueByMeasurementFrequencyAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Measurement Frequency</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueByMeasurementFrequencyAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Measurement Frequency [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsHeldForSaleNotPartOfDisposalGroupCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Asset, Held-for-Sale, Not Part of Disposal Group, Current, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsHeldForSaleNotPartOfDisposalGroupCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Asset, Held-for-Sale, Not Part of Disposal Group, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsHeldForSaleNotPartOfDisposalGroupCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Assets held for sale</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from issuance of common stock in connection with at-the-market offering, net of issuance costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Issuance of Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Share-based Compensation Arrangement by Share-based Payment Award [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_UnderwrittenPublicOfferingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Underwritten Public Offering [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_UnderwrittenPublicOfferingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Underwritten Public Offering</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_UnderwrittenPublicOfferingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Underwritten public offering.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_WarrantsToPurchaseSharesOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Warrants To Purchase Shares Of Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_WarrantsToPurchaseSharesOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Warrants To Purchase Shares Of Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_WarrantsToPurchaseSharesOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Warrants To Purchase Shares Of Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Entity Common Stock, Shares Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Common Stock, Shares Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Accumulated Other Comprehensive Income (Loss), Net of Tax, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accumulated Other Comprehensive Income (Loss), Net of Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accumulated other comprehensive income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Purchases of property and equipment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Payments to Acquire Property, Plant, and Equipment, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments to Acquire Property, Plant, and Equipment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of restricted stock awards granted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_UnvestedRestrictedStockAwardsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Unvested Restricted Stock Awards [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_UnvestedRestrictedStockAwardsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Unvested Restricted Stock Awards [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_UnvestedRestrictedStockAwardsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Unvested Restricted Common Stock Awards</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Assets_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Assets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Property, Plant and Equipment [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Property Plant And Equipment [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Statement [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restructuring Cost [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_TreasuryStockShare_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Treasury Stock Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_TreasuryStockShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Treasury Stock Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_TreasuryStockShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Treasury stock, shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Number of shares sold</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Sale of common stock, shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from issuance of common stock in connection with at-the-market offering, net of issuance costs, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringSettlementAndImpairmentProvisions_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Restructuring, Settlement and Impairment Provisions, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringSettlementAndImpairmentProvisions_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restructuring, Settlement and Impairment Provisions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringSettlementAndImpairmentProvisions_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Impairment for in-process research and development</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share, Diluted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Earnings Per Share, Diluted, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net income (loss per share) - diluted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Diluted EPS</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Research and Development, General and Administrative Expenses, and Restructuring Charges are Significant Segment Expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Segment Reporting Information, by Segment [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentRestatementTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Error Correction [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CityAreaCode_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">City Area Code</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CityAreaCode_lbl" xlink:role="http://www.xbrl.org/2003/role/label">City Area Code</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_AccuredRestructuringCost_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Restructuring costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_AccuredRestructuringCost_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Accured Restructuring cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_AccuredRestructuringCost_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accured Restructuring cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_TransactionCostsAllocatedToWarrantLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Transaction Costs Allocated To Warrant Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_TransactionCostsAllocatedToWarrantLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Transaction Costs Allocated To Warrant Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_TransactionCostsAllocatedToWarrantLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Transaction costs allocated to warrant liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ImpairmentLossesRelatedToRealEstatePartnerships_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Impairment losses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ImpairmentLossesRelatedToRealEstatePartnerships_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Impairment Losses Related to Real Estate Partnerships</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock under employee stock purchase plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period, Value, Employee Stock Purchase Plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingInformationLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Segment Reporting Information [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardGross_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of restricted stock, shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardGross_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period, Shares, Restricted Stock Award, Gross</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AwardDateAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Award Date [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LetterOfCreditMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Letter Of Credit Member</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LetterOfCreditMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Letter of Credit [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredCostsCapitalizedPrepaidAndOtherAssetsDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Property and equipment, net</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Property, Plant and Equipment, Net</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Cash, cash equivalents and restricted cash at beginning of period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Cash, cash equivalents and restricted cash at end of period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Including Discontinued Operation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingIncomeLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Income (Loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingIncomeLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Loss from operations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AwardDateDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Award Date [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accumulated Deficit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Retained Earnings [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ConsultingAndProfessionalServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Consulting and Professional Services [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ConsultingAndProfessionalServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Consulting and Professional Services [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ConsultingAndProfessionalServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Consulting and professional services</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash and Cash Equivalents</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash and Cash Equivalents [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensation_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Share-Based Payment Arrangement, Noncash Expense, Total</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensation_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement, Noncash Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total long-term liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities, Noncurrent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiabilityNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lease liability - operating lease, net of current portion</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiabilityNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease, Liability, Noncurrent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel1Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Quoted Prices in Active Markets for Identical Assets (Level 1)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel1Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Inputs, Level 1 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfStockLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Class Of Stock [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfStockLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class of Stock [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net cash provided by financing activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Provided by (Used in) Financing Activity, Including Discontinued Operation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentsFairValueDisclosure_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Investments, Fair Value Disclosure, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentsFairValueDisclosure_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Short-term investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentsFairValueDisclosure_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments, Fair Value Disclosure</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_USTreasuryAndGovernmentLongTermDebtSecuritiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">U.S. government agency securities and treasuries</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_USTreasuryAndGovernmentLongTermDebtSecuritiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">U S Treasury And Government Long Term Debt Securities [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_USTreasuryAndGovernmentLongTermDebtSecuritiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">US treasury and government long-term debt securities.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringChargesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restructuring Charges [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringChargesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Restructuring charges: expense acceleration</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_EmployeeStockPurchasePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Employee Stock Purchase Plan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_EmployeeStockPurchasePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Employee Stock Purchase Plan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NonoperatingIncomeExpenseAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Nonoperating Income (Expense) [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NonoperatingIncomeExpenseAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other income:</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CorporateDebtSecuritiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Corporate Debt Securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CorporateDebtSecuritiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Corporate Debt Securities [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxAuthorityDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Jurisdiction [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ClinicalResearchAndExternalCostsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Clinical Research and External Costs [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_ClinicalResearchAndExternalCostsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Clinical Research and External Costs [Member]</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt Securities Available For Sale [Table]</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityInteractiveDataCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Interactive Data Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityInteractiveDataCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Interactive Data Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementLocationDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Statement Location</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementLocationDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Income Location, Balance [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash flows from operating activities:</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FurnitureAndFixturesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Furniture and Fixtures [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FurnitureAndFixturesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Furniture and Fixtures</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="sybx_JefferiesLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Jefferies, LLC</link:label>
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  <xsd:element id="sybx_PreWarrantAtAPublicOfferingPrice" name="PreWarrantAtAPublicOfferingPrice" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="sybx_NetIncomePerShareTable" name="NetIncomePerShareTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sybx_TotalResearchAndDevelopmentExpense" name="TotalResearchAndDevelopmentExpense" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="sybx_AccuredRestructuringCost" name="AccuredRestructuringCost" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="sybx_LabEquipmentMember" name="LabEquipmentMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sybx_RestructuringIncludingLegalFees" name="RestructuringIncludingLegalFees" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="sybx_RocheCollaborationAndOptionAgreementMember" name="RocheCollaborationAndOptionAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sybx_PercentageOfCommonStockOwnershipToExerciseWarrant" name="PercentageOfCommonStockOwnershipToExerciseWarrant" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="sybx_TwoThousandSeventeenAndTwoThousandTwentyFiveEquityIncentiveAwardPlanMember" name="TwoThousandSeventeenAndTwoThousandTwentyFiveEquityIncentiveAwardPlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sybx_Scheduleoffairvalueassetsandliabilitiesmeasuredgrossunrealizedgainsandlossestabletextblock" name="Scheduleoffairvalueassetsandliabilitiesmeasuredgrossunrealizedgainsandlossestabletextblock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="sybx_PrepaidResearchAndDevelopmentExpenses" name="PrepaidResearchAndDevelopmentExpenses" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="sybx_JefferiesLLCMember" name="JefferiesLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sybx_FormerHeadquarterMember" name="FormerHeadquarterMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sybx_DecreaseInRightOfUseAssetAndOperatingLeaseLiabilities" name="DecreaseInRightOfUseAssetAndOperatingLeaseLiabilities" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="sybx_ReverseStockSplitApprovalDate" name="ReverseStockSplitApprovalDate" type="xbrli:dateItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="sybx_NonRule10B51ArrModifiedFlag" name="NonRule10B51ArrModifiedFlag" type="xbrli:booleanItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="sybx_CurrentLiabilitiesMember" name="CurrentLiabilitiesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sybx_OtherThanTemporaryImpairmentLossesInvestmentsNumberDebtSecuritiesAvailableForSale" name="OtherThanTemporaryImpairmentLossesInvestmentsNumberDebtSecuritiesAvailableForSale" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="sybx_TransactionCostsAllocatedToWarrantLiabilities" name="TransactionCostsAllocatedToWarrantLiabilities" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="sybx_PrepaidExpensesAndOtherCurrentAssetsTextBlock" name="PrepaidExpensesAndOtherCurrentAssetsTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="sybx_RelatedPartyTransactionCollaborationAgreementInitialTerm" name="RelatedPartyTransactionCollaborationAgreementInitialTerm" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="sybx_RelatedPartyTransactionCollaborationAgreementInitialTermExtended" name="RelatedPartyTransactionCollaborationAgreementInitialTermExtended" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="sybx_CommonStockAndWarrantsMember" name="CommonStockAndWarrantsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sybx_PreFundedWarrantsMember" name="PreFundedWarrantsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sybx_AzzurGroupLimitedLiabilityCompanyMember" name="AzzurGroupLimitedLiabilityCompanyMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sybx_IncreaseDecreaseInFairValueWarrantLiability" name="IncreaseDecreaseInFairValueWarrantLiability" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="sybx_GinkgoBioworksIncMember" name="GinkgoBioworksIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sybx_AvailableForSaleSecuritiesDisclosureTextBlock" name="AvailableForSaleSecuritiesDisclosureTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="sybx_TwoThousandSeventeenAndTwoThousandFifteenEquityIncentiveAwardPlanMember" name="TwoThousandSeventeenAndTwoThousandFifteenEquityIncentiveAwardPlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sybx_ClinicalResearchAndExternalCostsMember" name="ClinicalResearchAndExternalCostsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sybx_UnderwrittenPublicOfferingMember" name="UnderwrittenPublicOfferingMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sybx_CompensationAndBenefitsMember" name="CompensationAndBenefitsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sybx_AmortizedCostFairValue" name="AmortizedCostFairValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="sybx_PurchaseWarrantLiability" name="PurchaseWarrantLiability" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="sybx_ImpairmentForInProcessResearchAndDevelopment" name="ImpairmentForInProcessResearchAndDevelopment" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="sybx_ShareRepurchaseAbstract" name="ShareRepurchaseAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sybx_FederalAndStateDeferredTaxMember" name="FederalAndStateDeferredTaxMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sybx_ComputerAndOfficeEquipmentMember" name="ComputerAndOfficeEquipmentMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="sybx_CurrentPrePaidResearchAndDevelopment" name="CurrentPrePaidResearchAndDevelopment" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
</xsd:schema>
