c/o 5AM Ventures 4 Embarcadero Center, Suite 3110 San Francisco, CA 94111

Ventures VII Delaware Partners VII Delaware Schwab United States Parmar United States

Row 9 of each Reporting Person's cover page to this Schedule 13G sets forth the aggregate number of securities of the Issuer beneficially owned by such Reporting Person and is incorporated by reference. Ventures VII directly holds (i) 310,000 shares of common stock; and (ii) common warrants (the "Warrants") exercisable for up to 155,000 shares of common stock. The Warrants contain a provision (the "Beneficial Ownership Blocker"), which precludes the exercise of the Warrants to the extent that, following exercise, Ventures VII, together with its affiliates and other attribution parties, would own more than 9.99% of the common stock outstanding. In addition, pursuant to the Securities Purchase Agreement dated March 24, 2025 by and among the Issuer and certain investors, including Ventures VII (the "Purchase Agreement"), Ventures VII has agreed to purchase an additional (i) 465,000 shares of the Issuer's common stock (the "2nd Closing Shares") and (ii) common warrants (the "2nd Closing Warrants" and, together with the 2nd Closing Shares, the "2nd Closing Securities") exercisable for up to 232,500 shares of common stock in a second closing under the Purchase Agreement upon the Issuer's achievement of a regulatory milestone on or prior to October 31, 2026. The 2nd Closing Warrants, if issued, would contain a Beneficial Ownership Blocker that would preclude their exercise to the extent that, following exercise, Ventures VII, together with its affiliates and other attribution parties, would own more than 9.99% of the common stock outstanding. In the event that the Issuer terminates its SZN-8141 development program prior to October 31, 2026, then the Issuer is required to provide the investors under the Purchase Agreement, including Ventures VII, with a notice (the "Termination Notice"), after which Ventures VII would have the right, but not the obligation, to purchase the 2nd Closing Securities within the following 30 calendar days. Finally, at any time prior to the earlier of October 31, 2026 or the date of a Termination Notice, Ventures VII has the right, but not the obligation, to purchase all (but not a portion) of the 2nd Closing Securities. By virtue of this right, Ventures VII is considered to beneficially own the 2nd Closing Shares and, subject to the Beneficial Ownership Blocker, the shares issuable upon exercise of the 2nd Closing Warrants. Ventures VII is currently prohibited from exercising the Warrants and, if it was to acquire the 2nd Closing Securities, the 2nd Closing Warrants to the extent that such exercise would result in beneficial ownership of more than 908,387 shares of common stock. Partners VII is the sole general partner of Ventures VII and Schwab and Dr. Parmar are the managing members of Partners VII. Each of Partners VII, Schwab and Dr. Parmar shares voting and dispositive power over the securities held by Ventures VII.

Each Reporting Person beneficially owns 9.99% of the Issuer's common stock, which percentage is based upon the sum of (i) 3,281,169 shares of the Issuer's common stock outstanding as of March 25, 2025, as reported in the Issuer's Annual Report on Form 10-K filed with the Securities and Exchange Commission (the "SEC") on March 31, 2025; and (ii) 5,213,415 shares of the Issuer's common stock issued in the private placement of equity securities by the Issuer that closed on March 26, 2025, adjusted to give effect to the Warrants, 2nd Closing Shares and 2nd Closing Warrants to the extent that such securities may be acquired and exercised within 60 days hereof, as referenced herein. Due to field limitations of the EDGAR filing system, the percentages listed in Row 11 of each Reporting Person's cover page have been rounded down to 9.9%.

Row 5 of each Reporting Person's cover page to this Schedule 13G sets forth the sole power to vote or to direct the vote of securities of the Issuer beneficially owned by such Reporting Person and is incorporated by reference.

Row 6 of each Reporting Person's cover page to this Schedule 13G sets forth the shared power to vote or to direct the vote of securities of the Issuer beneficially owned by such Reporting Person and is incorporated by reference.

Row 7 of each Reporting Person's cover page to this Schedule 13G sets forth the sole power to dispose or to direct the disposition of securities of the Issuer beneficially owned by such Reporting Person and is incorporated by reference.

Row 8 of each Reporting Person's cover page to this Schedule 13G sets forth the shared power to dispose or to direct the disposition of securities of the Issuer beneficially owned by such Reporting Person and is incorporated by reference.