X0306 4 2022-09-15 0 0001701108 Spero Therapeutics, Inc. SPRO 0001557501 VINK PATRICK V.J.J. C/O SPERO THERAPEUTICS, INC. 675 MASSACHUSETTS AVENUE, 14TH FLOOR CAMBRIDGE MA 02139 1 0 0 0 Common Stock 2022-09-15 4 A 0 15000 0.00 A 15000 D Consists of restricted stock units ("RSUs"). Each RSU represents the right to receive one share of common stock upon vesting. The RSUs vest on September 15, 2023, subject to the Reporting Person's continued service through the applicable vesting date. /s/ Tamara Joseph, Attorney-in-Fact for Patrick V.J.J. Vink 2022-09-19