Prior to the Issuer's initial public offering (the "IPO"), AH Bio IV, for itself and as nominee for AH Bio IV-B, AH Annual 2022, AH Annual 2022-B, AH Annual 2022-QC and CLF III, purchased 40,000,000 shares of the Issuer's Series A Preferred Stock for an aggregate purchase price of $40 million. In connection with the closing of the IPO, on August 7, 2026, the Series A Preferred Stock automatically converted into shares of common stock on a 4.38-for-1 basis, resulting in the issuance to AH Bio IV of an aggregate of 9,132,420 shares of common stock for no additional consideration. On August 7, 2026, AH Bio IV, for itself and as nominee for AH Bio IV-B, AH Annual 2022, AH Annual 2022-B, AH Annual 2022-QC and CLF III, also purchased 1,100,000 shares of the Issuer's common stock from the underwriters of the IPO at the IPO price of $18.00 per share, for an aggregate purchase price of $19.8 million. The source of funds for the purchases of securities described above was capital contributions by the general and limited partners of AH Bio IV and the funds for which it serves as nominee.

Investors' Rights Agreement Pursuant to an investors' rights agreement (the "Investors' Rights Agreement") dated September 3, 2025 by and among the Issuer and certain holders of shares of the Issuer's capital stock, including AH Bio IV, such holders will be entitled to certain registration rights with respect to the shares of common stock issued upon conversion of their Series A Preferred Stock ("Registrable Securities"). Subject to specified limitations, at any time beginning 180 days after the effective date of the registration statement for the IPO, the holders of a majority of Registrable Securities then outstanding may request that the Issuer register all or a portion of their Registrable Securities having an anticipated aggregate offering price, net of selling expenses, that exceeds $20 million, on a Form S-1 registration statement. The Issuer will not be required to effect more than one Form S-1 registration statement pursuant to these demand registration rights. If the Issuer is qualified to file a registration statement on Form S-3, holders of Registrable Securities may request the Issuer to register their Registrable Securities on Form S-3 if the anticipated aggregate offering price, net of selling expenses, would be at least $5 million. The Issuer will not be required to effect more than two registrations on Form S-3 within any 12-month period. In the event that the Issuer proposes to register any of its securities under the Securities Act, either for its own account or for the account of other security holders, the holders of Registrable Securities will be entitled to certain piggyback registration rights allowing such holders to include their Registrable Securities in such registration, subject to certain marketing and other limitations. The Investors' Rights Agreement contains customary cross-indemnification provisions, pursuant to which the Issuer is obligated to indemnify the selling securityholders and other parties in the event of material misstatements or omissions in the registration statement attributable to the Issuer and the selling securityholders are obligated to indemnify the Issuer for material misstatements or omissions in the registration statement attributable to them, subject to certain limitations. The registration rights granted under the Investors' Rights Agreement will terminate upon the earliest to occur of (i) the closing of a "Deemed Liquidation Event," as such term is defined in the Issuer's amended and restated certificate of incorporation as in effect prior to the IPO, (ii) with respect to each holder, the date on which (x) such holder together with its affiliates holds less than 1% of the Issuer's outstanding capital stock and (y) all Registrable Securities held by such holder may immediately be sold during a three-month period pursuant to Rule 144 of the Securities Act or another similar exemption, and (iii) the third anniversary of the completion of the IPO. The foregoing description of the Investors' Rights Agreement does not purport to be complete and is qualified in its entirety by reference to the full text of the Investors' Rights Agreement, which is filed as Exhibit 99.2 hereto and incorporated by reference herein. Lock-Up Agreement In connection with the IPO, each of the Issuer's directors and executive officers, and the holders of substantially all of the Issuer's pre-IPO common stock and securities convertible into or exchangeable for its capital stock, including AH Bio IV, entered into a customary lock-up agreement with the underwriters with respect to its common stock (each, a "Lock-up Agreement"), pursuant to which they agreed, subject to certain customary exceptions, for a period of 180 days after August 5, 2026, not to (and to cause their affiliates not to) offer, sell, contract to sell, pledge, grant any option, right or warrant to purchase, purchase any option or contract to sell, lend, or otherwise transfer or dispose of or hedge any of their common stock or securities convertible into or exchangeable for shares of common stock, except with the prior written consent of Goldman Sachs & Co. LLC, Jefferies LLC and TD Securities (USA) LLC on behalf of the underwriters. The foregoing description of the Lock-up Agreement does not purport to be complete and is qualified in its entirety by reference to the full text of the form of the Lock-up Agreement, which is filed as Exhibit 99.3 hereto and incorporated by reference herein.

Exhibit 24.1 Power of Attorney for Marc L. Andreessen, dated June 23, 2023. Exhibit 24.2 Power of Attorney for Benjamin A. Horowitz, dated June 22, 2023. Exhibit 99.1 Joint Filing Agreement Exhibit 99.2 Investors' Rights Agreement (incorporated by reference to Exhibit 4.2 to the Issuer's Registration Statement on Form S-1 (Registration No. 333-297456), filed with the SEC on July 15, 2026). Exhibit 99.3 Form of Lock-up Agreement (incorporated by reference to Annex II to the Underwriting Agreement filed as Exhibit 1.1 to Amendment No. 1 to the Issuer's Registration Statement on Form S-1 (Registration No. 333-297456), filed with the SEC on July 30, 2026).