X0206 3 2024-02-05 0 0001907108 Lexeo Therapeutics, Inc. LXEO 0002009350 See Tai Sandi C/O LEXEO THERAPEUTICS, INC. 345 PARK AVENUE SOUTH, FLOOR 6 NEW YORK NY 10010 0 1 0 0 Chief Development Officer Common Stock 16625 D Employee Stock Option (right to buy) 12.72 2033-11-29 Common Stock 64189 D Employee Stock Option (right to buy) 14.48 2034-01-04 Common Stock 30000 D Employee Stock Option (right to buy) 17.00 2034-02-01 Common Stock 69750 D The reported securities are restricted stock units ("RSUs"). Each RSU represents a contingent right to receive one share of Common Stock of the Issuer. Twenty-five percent (25%) of the RSUs shall vest on February 15, 2025, and 1/16th of the RSUs shall vest in quarterly installments thereafter on the Issuer's standard quarterly vesting dates, subject to the Reporting Person's continued service through each applicable vesting date. 25% of the shares underlying the option vest and become exercisable on October 30, 2024, and 1/48th of the shares underlying the option shall vest in monthly installments thereafter, subject to the Reporting Person's continuous service. 25% of the shares underlying the option vest and become exercisable on January 5, 2025, and 1/48th of the shares underlying the option shall vest in monthly installments thereafter, subject to the Reporting Person's continuous service. 25% of the shares underlying the option vest and become exercisable on February 2, 2025, and 1/48th of the shares underlying the option shall vest in monthly installments thereafter, subject to the Reporting Person's continuous service. /s/ Jenny Robertson, attorney-in-fact 2024-02-06