144 0001994972 XXXXXXXX LIVE 0001907108 Lexeo Therapeutics, Inc. 001-41855 345 PARK AVENUE SOUTH FLOOR 6 NEW YORK NY 10010 (212) 547-9879 Adler Eric Officer Common Fidelity Brokerage Services LLC

900 Salem Street Smithfield RI 02917

615 5703.88 72987327 11/18/2025 NASDAQ Common 11/17/2025 Restricted Stock Vesting Issuer N 615 11/17/2025 Compensation N Eric Adler

345 Park Avenue South Floor 6 New York NY 10010

Common 08/18/2025 608 2838.27 Eric Adler

345 Park Avenue South Floor 6 New York NY 10010

Common 10/17/2025 3382 30242.18 Sale includes an amount necessary to cover a tax obligation resulting from the settlement of a vested equity award distribution. 11/18/2025 /s/ Jennifer Ruchti, as a duly authorized representative of Fidelity Brokerage Services LLC, as attorney-in-fact for Eric Adler