X0508 4 2026-02-02 0001776111 MBX Biosciences, Inc. MBX 0002030246 Azoulay Salomon C/O MBX BIOSCIENCES, INC. 11711 N. MERIDIAN STREET, SUITE 300 CARMEL IN 46032 false true false false Chief Medical Officer false Common Stock 2026-02-02 4 A false 15000 0 A 15000 D Stock option (right to buy) 39.07 2026-02-02 4 A false 70000 0 A 2036-02-02 Common Stock 70000 70000 D Represents the grant of restricted stock units (RSUs). The RSUs will vest over a four (4) year period in equal quarterly installments, subject to the Reporting Person's continued service on such vesting date. The shares underlying this option vest and become exercisable in forty eight (48) equal monthly installments, beginning on March 2, 2026, subject to the Reporting Person's continued service on such vesting date. /s/ Richard Bartram, attorney-in-fact 2026-02-03