X0202 SCHEDULE 13G 0002044377 XXXXXXXX LIVE Common Stock, $0.0001 par value per share 05/11/2026 0001882782 Odyssey Therapeutics, Inc. 67613T104 51 Sleeper Street, Suite 800 Boston MA 02210 Rule 13d-1(c) Lightspeed Venture Partners XV-B (Ignite), L.P. b DE 0.00 3608443.00 0.00 3608443.00 3608443.00 7.6 PN Lightspeed General Partner XV-B (Ignite), L.P. b DE 0.00 3608443.00 0.00 3608443.00 3608443.00 7.6 PN Lightspeed Ultimate General Partner XV-B (Ignite), L.L.C. b DE 0.00 3608443.00 0.00 3608443.00 3608443.00 7.6 OO Odyssey Therapeutics, Inc. 51 Sleeper Street, Suite 800, Boston, MA, 02210 . The names of the persons filing this report (collectively, the "Reporting Persons") are: Lightspeed Venture Partners XV-B (Ignite), L.P. ("Lightspeed XV-B") Lightspeed General Partner XV-B (Ignite), L.P. ("LGP XV-B") Lightspeed Ultimate General Partner XV-B (Ignite), L.L.C. ("LUGP XV-B") The Reporting Persons expressly disclaim status as a "group" for purposes of this Schedule 13G. c/o Lightspeed Venture Partners 2200 Sand Hill Road Menlo Park, CA 94025 Lightspeed XV-B Delaware LGP XV-B Delaware LUGP XV-B Delaware Y Row 9 of each Reporting Person's cover page to this Schedule 13G sets forth the aggregate number of shares of common stock of the Issuer beneficially owned by such Reporting Person and is incorporated by reference. The Reporting Persons' ownership of the Issuer's securities consists of 3,608,443 shares of common stock directly held by Lightspeed XV-B. LUGP XV-B serves as the sole general partner of LGP XV-B, which serves as the sole general partner of Lightspeed XV-B. Row 11 of each Reporting Person's cover page to this Schedule 13G sets forth the percentages of the shares of common stock of the Issuer beneficially owned by such Reporting Person and is incorporated by reference. The percentage set forth in each row 11 is based upon 47,174,156 shares of common stock outstanding as of May 11, 2026, as reported in the Issuer's prospectus dated May 7, 2026 filed with the Securities and Exchange Commission (the "SEC") on May 8, 2026. 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. Y Y Y Y Y N By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under § 240.14a-11. Exhibit 99.1 Joint Filing Agreement Lightspeed Venture Partners XV-B (Ignite), L.P. /s/ Ravi Mhatre 05/18/2026 Lightspeed General Partner XV-B (Ignite), L.P. /s/ Ravi Mhatre 05/18/2026 Lightspeed Ultimate General Partner XV-B (Ignite), L.L.C. /s/ Ravi Mhatre 05/18/2026 Note 1: By Lightspeed General Partner XV-B (Ignite), L.P., its General Partner, By Lightspeed Ultimate General Partner XV-B (Ignite), L.L.C., its General Partner, By Ravi Mhatre, Managing Member