X0306 4 2021-12-20 0 0001619856 Caribou Biosciences, Inc. CRBU 0001670579 Haurwitz Rachel E. C/O CARIBOU BIOSCIENCES, INC. 2929 7TH STREET, SUITE 105 BERKELEY CA 94710 1 1 0 0 President and CEO Option to purchase Common Stock 15.16 2021-12-20 4 A 0 411000 0.00 A 2031-12-19 Common Stock 411000 411000 D The shares subject to this option will vest in equal monthly installments starting on the first monthly anniversary of the grant date until the option is fully vested on December 20, 2025, subject to the reporting person's continued service to the Issuer through the applicable vesting dates. /s/ Barbara G. McClung, as attorney-in-fact 2021-12-21