Prior to the Issuer's initial public offering (the "IPO"), (i) the Fund purchased an aggregate of 12,924,620 shares of Series C preferred stock and (ii) the Nexus Fund III purchased an aggregate of 5,889,699 shares of Series C preferred stock. The aggregate purchase price of the foregoing was $29,999,997. In connection with the closing of the IPO, on November 7, 2025, the Series C preferred stock automatically converted into shares of common stock on a 1-for-8.518 basis. The Fund and the Nexus Fund III also purchased 1,157,096 and 92,904 shares of common stock, respectively, from the underwriters of the IPO at the IPO price of $16.00 per share, for an aggregate purchase price of $20,000,000. All purchases of the securities described herein were for cash and were funded by working capital of the Fund and the Nexus Fund III, as applicable.

Lock-up Agreements The holders of substantially all of the Issuer's pre-IPO capital stock, including the Fund and the Nexus Fund III, and each of the Issuer's directors, entered into lock-up agreements (the "Lock-Up Agreements") with the representatives of the underwriters of the Issuer's IPO. Pursuant to the Lock-Up Agreements, neither the Fund nor the Nexus Fund III is permitted, with limited exceptions, for a period of 180 days from November 7, 2025, to dispose of or hedge any of the Issuer's securities, except with the prior written consent of Morgan Stanley & Co. LLC, Leerink Partners LLC and Evercore Group L.L.C. The description of the Lock-Up Agreements contained in this Item 6 is qualified in its entirety by reference to the full text of the form of Lock-up Agreement filed as Exhibit 99.2 to this Schedule 13D and incorporated by reference herein. Third Amended and Restated Investors' Rights Agreement On October 30, 2024, certain investors of the Issuer, including the Fund and the Nexus Fund III, entered into a third amended and restated investors' right agreement (the "Investors' Rights Agreement") with the Issuer, pursuant to which the Issuer agreed to register for resale certain shares of common stock and other equity securities of the Issuer that are held by the investors party thereto (the "Registrable Securities"). Pursuant to the Investors' Rights Agreement, beginning 180 days after the effective date of the registration statement filed in connection with the IPO, the Issuer will file a registration statement registering the resale of the Registrable Securities upon the request of holders of at least a majority of the outstanding Registrable Securities. The investors may request a maximum of two registrations pursuant to this provision. In addition, holders of at least 20% of the outstanding Registrable Securities may request the Issuer to file a registration statement on Form S-3, if eligible, to sell Registrable Securities with an anticipated aggregate offering amount of at least $5.0 million net of certain expenses related to the offering. The investors may request a maximum of two registration statements on Form S-3 in a 12-month period. The Issuer will be responsible for certain expenses relating to such registrations and indemnify the stockholders against certain liabilities. The investors are also entitled to customary "piggyback" registration rights, subject to certain requirements and conditions. The registration rights granted under the Investors' Rights Agreement will terminate upon the earlier of (i) a deemed liquidation event or certain other events constituting sale of the Issuer, (ii) such time after the IPO when all Registrable Securities could be sold under Rule 144 of the Securities Act of 1933, as amended, or a similar exemption without limitation during a three-month period without registration or (iii) the fifth anniversary of the IPO. The description of the Investors' Rights Agreement contained in this Item 6 is qualified in its entirety by reference to the full text of the Investors' Rights Agreement filed as Exhibit 99.3 to this Schedule 13D and incorporated by reference herein. Equity Awards Derek DiRocco, a Partner at RA Capital, is a member of the Board of Directors of the Issuer. From time to time, Dr. DiRocco may receive stock options or other awards of equity-based compensation pursuant to the Issuer's compensation arrangements for non-employee directors. Pursuant to an agreement with RA Capital, Dr. DiRocco is obligated to transfer any securities issued under any such stock options or other awards, or the economic benefit thereof, to RA Capital.

Exhibit 99.1 Joint Filing Agreement Exhibit 99.2 Form of Lock-up Agreement (incorporated by reference to Exhibit A to the Form of Underwriting Agreement filed as Exhibit 1.1 to the Issuer's Registration Statement on Form S-1, as amended (Registration No. 333-290793), filed with the SEC on October 17, 2025). Exhibit 99.3 Third Amended and Restated Investors' Rights Agreement, dated as of October 30, 2024, by and among Evommune, Inc. and the investors party thereto (incorporated by reference to Exhibit 4.2 to the Issuer's Registration Statement on Form S-1 (Registration No. 333-290793), filed with the SEC on October 9, 2025).