X0306 4 2023-01-18 0 0001759138 Cabaletta Bio, Inc. CABA 0001903997 Das Arun C/O CABALETTA BIO, INC. 2929 ARCH STREET, SUITE 600 PHILADELPHIA PA 19104 0 1 0 0 Chief Business Officer Stock Option (Right to Buy) 11.09 2023-01-18 4 A 0 150000 0.00 A 2033-01-17 Common Stock 150000 150000 D 25% of the shares underlying this option shall vest and become exercisable on January 18, 2024, with the remainder vesting in twelve substantially equal quarterly installments thereafter, subject to the reporting person's continued service on each such vesting date. By: /s/ Michael Gerard, as Attorney-in-Fact 2023-01-27