X0206 3 2019-10-24 0 0001759138 Cabaletta Bio, Inc. CABA 0001400717 Simon Mark C/O CABALETTA BIO, INC. 2929 ARCH STREET, SUITE 600 PHILADELPHIA PA 19104 1 0 0 0 Series A-1 Preferred Stock Common Stock 18144 D Stock Option (Right to Buy) 1.01 2028-10-28 Common Stock 27968 D Stock Option (Right to Buy) 6.30 2029-02-18 Common Stock 18460 D The Series A-1 Preferred Stock is convertible into shares of the Issuer's Common Stock on a one-for-1.5 basis. Upon the closing of the Issuer's initial public offering, all shares of Series A-1 Preferred Stock will convert into shares of Common Stock of the Issuer. The Series A-1 Preferred Stock has no expiration date. This option vests in eight equal quarterly installments beginning on October 11, 2018. This option vests in eight equal quarterly installments beginning on February 19, 2019. Exhibit 24 - Power of Attorney /s/ Mark Simon 2019-10-24