X0306 4 2022-01-25 0 0001619856 Caribou Biosciences, Inc. CRBU 0001897621 Rizvi Syed Ali-aamir C/O CARIBOU BIOSCIENCES, INC. 2929 7TH STREET, SUITE 105 BERKELEY CA 94710 0 1 0 0 Chief Medical Officer Common stock 2022-01-25 4 A 0 60000 0.00 A 65000 D Option to purchase common stock 10.64 2022-01-25 4 A 0 161250 0.00 A 2032-01-24 Common stock 161250 161250 D This reflects restricted stock units ("RSUs") that vest in four equal annual installments beginning on January 18, 2023, subject to the reporting person's continued services to the Issuer through the applicable vesting dates. The RSUs will be settled in stock within 30 days after each vesting date. 1/4th of the shares subject to this option will vest on January 18, 2023 and an additional 1/48th of the aggregate number of shares subject to the option will vest on the corresponding day of each month thereafter, subject to the reporting person's continued services to the Issuer through the applicable vesting dates. /s/ Barbara G. McClung, as attorney-in-fact 2022-01-25