6. Debt

Avenue Loan

On January 7, 2026 (the “Avenue Closing Date”), the Company entered into a Loan and Security Agreement (the “Avenue Loan and Security Agreement”) and a Supplement to the Loan and Security Agreement (together with the Avenue Loan and Security Agreement, the “Avenue Loan Agreement”), with Avenue Capital Management II, L.P., as administrative agent and collateral agent (the “Agent”) and Avenue Venture Opportunities Fund II, L.P., as lender (the “Lender”, together with the Agent, “Avenue”).

The Avenue Loan Agreement makes available to the Company term loans in an aggregate principal amount of up to $50.0 million with (i) $15.0 million funded within 5 business days after the Avenue Closing Date (“Tranche 1”), (ii) up to $10.0 million to be made available to the Company between March 1, 2026 and September 30, 2026, subject to, among other things, the Company’s achievement of a key regulatory milestone related to the Company’s development of TA-ERT for the treatment of Sanfilippo Syndrome Type B (“MPS IIIB”) (“Tranche 2”) and (iii) up to $15.0 million to be made available to the Company between September 1, 2026 and March 31, 2027, subject to, among other things, the Company’s achievement of an additional key regulatory milestone with respect to the Company’s development of TA-ERT for the treatment of MPS IIIB (“Tranche 3”). The Lender may make additional term loans of up to an additional $10.0 million (the “Discretionary Tranche 4” and collectively with Tranche 1, Tranche 2 and Tranche 3, the “Avenue Loans”), to be funded between October 1, 2027 and June 30, 2028, subject to, among other things, (i) the Company’s achievement of a certain commercial milestone and (ii) the mutual written agreement of the Company and the Lender (upon the Lender’s investment committee approval). The Avenue Loans bear interest at an annual rate equal to the greater of (x) the sum of 5.25% plus the prime rate as reported in The Wall Street Journal and (y) 12.25%. The Avenue Loans are secured by a lien upon and security interest in all of the Company’s assets, including intellectual property, subject to agreed exceptions. The maturity date of the Avenue Loans is July 1, 2029 (the “Avenue Maturity Date”). The Avenue Loan Agreement does not contain any minimum cash requirement or other financial covenants. As of March 31, 2026, the stated interest rate of the Avenue Loans was 12.25%.

The Company will make interest only payments on the Avenue Loans until the 12-month anniversary of the Avenue Closing Date, subject to (i) a 6-month extension, so long as at least $5.0 million from Tranche 2 has been funded and (ii) an additional 12-month extension if the Company achieves the Tranche 3 milestone. The Avenue Loans principal is repayable in equal monthly installments from the end of interest only period to the Avenue Maturity Date.

The Company may, at its option at any time, prepay the Avenue Loans in their entirety by paying the then-outstanding principal balance and all accrued and unpaid interest on the Avenue Loans, subject to a prepayment fee equal to (i) 3.0% of the principal amount outstanding if the prepayment occurs on or prior to the first anniversary following the Avenue Closing Date, (ii) 2.0% of the principal amount outstanding if the prepayment occurs after the first anniversary following the Avenue Closing Date, but on or prior to the second anniversary following the Avenue Closing Date, and (iii) 1.0% of the principal amount outstanding if the prepayment occurs after the second anniversary following the Avenue Closing Date. The Company will pay a final payment of 4.0% of the aggregate commitment amounts for Tranche 1, Tranche 2 and Tranche 3, which shall be increased to include the commitment amount of Discretionary Tranche 4 upon the funding of such tranche, on the earlier of (x) the Avenue Maturity Date and (y) the date that the Company prepays all of the outstanding principal amount of the Avenue Loans in full (“Avenue Final Payment”). On the Avenue Closing Date, the Company paid to the Lender a commitment fee of $0.4 million.

The Avenue Loan Agreement contains customary representations, warranties and covenants, including covenants by the Company limiting additional indebtedness, liens, guaranties, mergers and consolidations, substantial asset sales, investments and loans, certain corporate changes, transactions with affiliates and fundamental changes. The Avenue Loan Agreement provides for events of default customary for term loans of this type, including but not limited to non-payment, breaches or defaults in the performance of covenants, insolvency, bankruptcy and the occurrence of a material adverse effect on the Company. After the occurrence of an event of default, the Agent may (i) accelerate payment of all obligations, impose an increased rate of interest, and terminate the Lender’s commitments under the Avenue Loan Agreement and (ii) exercise any other right or remedy provided by contract or applicable law. As of March 31, 2026, the Company was in compliance with all covenants under the Avenue Loan Agreement.

Pursuant to the Avenue Loan Agreement, following the filing of the Company’s annual report on Form 10-K for the fiscal year ending December 31, 2025 which occurred on March 9, 2026, the Lender has the right to convert up to $4.0 million of the outstanding principal of the Avenue Loans (the “Avenue Conversion Option”) at a price of $60.00 per share, subject to certain terms and conditions, including beneficial ownership limitations. In addition, subject to applicable law, the Lender had the right to participate in certain equity financing transactions of the Company in an aggregate amount of up to $1.0 million on the same terms, conditions and pricing offered by the Company to other investors participating in such financing transaction (such right, the “Participation Right”). The Participation Right terminated in April 2026.

At issuance of the Avenue Loans, the Company recorded the debt net of debt discount and costs which included $7.6 million for the grant date fair value of the Avenue Warrant and Avenue Conversion Option (discussed below), Avenue Final Payment of $1.6 million and issuance costs of $1.2 million.

As of March 31, 2026, the carrying value of the Avenue Loans was $6.5 million, consisting of the outstanding principal under Tranche 1 of $15.0 million, plus the Avenue Final Payment of $1.6 million, less unamortized debt discount and costs of $10.1 million, which are being amortized using the effective interest method over the life of the Avenue Loans.

Avenue Warrant

In connection with the Avenue Loans, the Company issued to the Lender a warrant (the “Avenue Warrant”) to purchase up to $3.2 million worth of shares of the Company’s common stock on March 9, 2026. Prior to the issuance of the Avenue Warrant, the Lender was entitled to receive a payment of $6.4 million in the event a change of control had occurred prior to the issuance of the Avenue Warrant (the “Success Fee”). The obligation to pay the Lender the Success Fee terminated upon the issuance of the Avenue Warrant. The Avenue Warrant will expire on January 31, 2031 (the “Avenue Warrant Expiration Date”) and has an exercise price equal to $50.00 per share, provided that any exercise of such Avenue Warrant is subject to certain beneficial ownership limitations. In addition, upon a change of control, the Lender is entitled to receive the shares of the Company's common stock underlying the Avenue Warrant without payment of the exercise price.

The Lender may exercise the Avenue Warrant at any time, or from time to time up to and including the Avenue Warrant Expiration Date, by making a cash payment equal to the exercise price multiplied by the quantity of shares. The Lender may also exercise the Avenue Warrant on a cashless basis by receiving a net number of shares calculated pursuant to the formula set forth in the Avenue Warrant. The Avenue Warrant is subject to anti-dilution adjustments for stock dividends, stock splits, and reverse stock splits.

Avenue Warrant Liability

Although the Avenue Warrant wasn't legally issued until March 9, 2026 (the “Avenue Warrant Issue Date“), the Avenue Warrant was considered issued and outstanding as of the Avenue Closing Date for accounting purposes. The Avenue Warrant met the criteria for a derivative classification under ASC 815. As of the Avenue Closing Date, the Avenue Warrant did not have a fixed number of shares to be issued and therefore did not qualify for equity classification and was accounted for as a derivative liability at an initial fair value of $3.8 million under the Monte Carlo Method, with changes in fair value recognized on the condensed statements of operations and comprehensive loss during the three months ended March 31, 2026.

Upon legal issuance of the Avenue Warrant on March 9, 2026, the shares into which the Avenue Warrant will be issued became fixed and therefore the Company reassessed its accounting treatment under ASC 815-40-15-7 using the prescribed two-step analysis. The Company concluded that Section 4.3 of the Avenue Warrant, which provides for automatic exchange of the Avenue Warrant for a fixed number of shares without payment of the exercise price upon a change of control, precludes the Avenue Warrant from being considered indexed to the Company’s own stock under Step 2 of ASC 815-40-15-7C through 7E. As such, the Avenue Warrant remains a derivative liability and was remeasured to fair value with changes in fair value recognized on the condensed statements of operations and comprehensive loss during the three months ended March 31, 2026.

Avenue Conversion Option

As discussed above, the Avenue Conversion Option allows the Lender to convert up to $4.0 million of the outstanding principal of the Avenue Loans at a price of $60.00 per share. At inception on the Avenue Closing Date, this feature was initially accounted for as an embedded derivative liability due to variable settlement terms at an initial fair value of $3.7 million under the Monte Carlo Method, with changes in fair value recognized on the condensed statements of operations and comprehensive loss during the three months ended March 31, 2026.

Upon legal issuance of the Avenue Warrant on March 9, 2026, the Company reassessed its accounting treatment under ASC 815-40-15-7 using the prescribed two-step analysis and concluded that the Avenue Conversion Option qualified for equity

classification because the settlement terms became fixed and the Avenue Conversion Option satisfied both the indexation and classification criteria. As such, the derivative liability was remeasured to fair value of $3.7 million and reclassified to additional paid-in capital, with no further remeasurement required thereafter.

As of the date of this filing, 64,000 shares remain outstanding under the Avenue Warrant at an exercise price of $50.00 and Avenue had not exercised the Avenue Conversion Option.