X0306 4 2022-03-04 0 0001619856 Caribou Biosciences, Inc. CRBU 0001871131 Kanner Steven C/O CARIBOU BIOSCIENCES, INC. 2929 7TH STREET, SUITE 105 BERKELEY CA 94710 0 1 0 0 Chief Scientific Officer Common Stock 2022-03-04 4 M 0 9171 2.69 A 226090 D Common Stock 2022-03-04 4 M 0 1549 4.11 A 227639 D Option to purchase Common Stock 2.69 2022-03-04 4 M 0 9171 0.00 D 2029-09-30 Common Stock 9171 122963 D Option to purchase Common Stock 4.11 2022-03-04 4 M 0 1549 0.00 D 2031-03-29 Common Stock 1549 230365 D Due to a rounding error, the exercise price for this stock option was inadvertently originally reported as $2.68 per share on the reporting person's Form 3 filed on July 22, 2021. Includes 1,888 shares purchased pursuant to the Issuer's 2021 Employee Stock Purchase Plan on February 15, 2022 for $9.85 per share. 1/4th of the shares subject to this option vested on October 1, 2020 and an additional 1/48th of the aggregate number of shares subject to the option have vested or will vest on the corresponding day of each month thereafter until the option is fully vested, subject to the reporting person's continued service to the Issuer through the applicable vesting dates. 1/4th of the shares subject to this option vested on March 2, 2022 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 until the option is fully vested, subject to the reporting person's continued service to the Issuer through the applicable vesting dates. /s/ Barbara G. McClung, at attorney-in-fact 2022-03-07