Organization and Basis of Presentation (Policies)	3 Months Ended
Mar. 31, 2026
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Liquidity and Capital Resources	Liquidity and Capital Resources The accompanying unaudited condensed financial statements have been prepared assuming the Company will continue as a going concern, which assumes that the Company will realize its assets and satisfy its liabilities in the normal course of business. As of March 31, 2026, the Company had cash, cash equivalents and marketable securities of $522.1 million, which the Company believes will be sufficient to fund its planned operations for a period of, at least, twelve months following the date of filing of this report.
Basis of Presentation	Basis of Presentation The accompanying unaudited interim condensed financial statements have been prepared in conformity with generally accepted accounting principles in the United States of America (“U.S. GAAP”) stated in U.S. dollars and include all adjustments necessary for the fair presentation of the Company’s interim financial information. The condensed balance sheet data at December 31, 2025 was derived from the audited financial statements included in Septerna’s Annual Report on Form 10-K for the year ended December 31, 2025 as filed with the Securities and Exchange Commission (“SEC”) on March 9, 2026. These interim unaudited condensed financial statements should be read in conjunction with the audited financial statements and related notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2025.
Significant Accounting Policies	Significant Accounting Policies During the three months ended March 31, 2026, there were no changes to the Company’s significant accounting policies as described in Note 2 of the audited financial statements for the year ended December 31, 2025.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements In July 2025, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2025-05, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses for Accounts Receivable and Contract Assets, which provides a practical expedient that assumes that current conditions as of the balance sheet date do not change for the remaining life of the asset in developing reasonable and supportable forecasts during the application of the current expected credit loss model for current accounts receivable and current contract assets arising from transactions under ASC 606. ASU 2025-05 is effective for fiscal years beginning after December 15, 2025 and interim reporting periods within those annual reporting periods. Early adoption is permitted. The Company determined there is no impact of adopting ASU 2025-05 as it does not develop forecasts as part of estimating expected credit losses.
Accounting Pronouncements Not Yet Adopted	Accounting Pronouncements Not Yet Adopted From time to time, new accounting pronouncements are issued by the FASB, under its Accounting Standards Codification (“ASC”) or other standard setting bodies, and adopted by the Company as of the specified date. In November 2024, the FASB issued ASU No. 2024-03, Income Statement—Reporting Comprehensive Income—Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses, an accounting standard update that requires the Company to disclose more detailed information about the types of expenses (including employee compensation, depreciation, and amortization) included in each relevant income statement expense caption. The ASU is effective for fiscal years beginning after December 15, 2026, and interim reporting periods beginning after December 15, 2027. Early adoption is permitted. The Company is currently evaluating the impact that this update will have on its disclosures.

Organization and Basis of Presentation (Policies)

3 Months Ended

Mar. 31, 2026

Organization, Consolidation and Presentation of Financial Statements [Abstract]

The accompanying unaudited condensed financial statements have been prepared assuming the Company will continue as a going concern, which assumes that the Company will realize its assets and satisfy its liabilities in the normal course of business.

As of March 31, 2026, the Company had cash, cash equivalents and marketable securities of $522.1 million, which the Company believes will be sufficient to fund its planned operations for a period of, at least, twelve months following the date of filing of this report.

Basis of Presentation

The accompanying unaudited interim condensed financial statements have been prepared in conformity with generally accepted accounting principles in the United States of America (“U.S. GAAP”) stated in U.S. dollars and include all adjustments necessary for the fair presentation of the Company’s interim financial information.

The condensed balance sheet data at December 31, 2025 was derived from the audited financial statements included in Septerna’s Annual Report on Form 10-K for the year ended December 31, 2025 as filed with the Securities and Exchange Commission (“SEC”) on March 9, 2026. These interim unaudited condensed financial statements should be read in conjunction with the audited financial statements and related notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2025.

Significant Accounting Policies

During the three months ended March 31, 2026, there were no changes to the Company’s significant accounting policies as described in Note 2 of the audited financial statements for the year ended December 31, 2025.

Recently Adopted Accounting Pronouncements

In July 2025, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2025-05, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses for Accounts Receivable and Contract Assets, which provides a practical expedient that assumes that current conditions as of the balance sheet date do not change for the remaining life of the asset in developing reasonable and supportable forecasts during the application of the current expected credit loss model for current accounts receivable and current contract assets arising from transactions under ASC 606. ASU 2025-05 is effective for fiscal years beginning after December 15, 2025 and interim reporting periods within those annual reporting periods. Early adoption is permitted. The Company determined there is no impact of adopting ASU 2025-05 as it does not develop forecasts as part of estimating expected credit losses.

Accounting Pronouncements Not Yet Adopted

From time to time, new accounting pronouncements are issued by the FASB, under its Accounting Standards Codification (“ASC”) or other standard setting bodies, and adopted by the Company as of the specified date.

In November 2024, the FASB issued ASU No. 2024-03, Income Statement—Reporting Comprehensive Income—Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses, an accounting standard update that requires the Company to disclose more detailed information about the types of expenses (including employee compensation, depreciation, and amortization) included in each relevant income statement expense caption. The ASU is effective for fiscal years beginning after December 15, 2026, and interim reporting periods beginning after December 15, 2027. Early adoption is permitted. The Company is currently evaluating the impact that this update will have on its disclosures.