Form 4 for CRBU Caribou Biosciences, Inc.

Accepted 2026-02-24 00:00:00 ET · period of report 2026-02-20 · accession 0001754067-26-000002 · SEC index · Original document

Summary rows

Aggregated the way they appear in lists: one row per insider, transaction code and security table.

X	Filed	Traded	Ticker	Insider	Title	Type	Price	Qty	Owned	ΔOwn	Value
D	2026-02-24	2026-02-20	CRBU	Kelly Timothy P	CTO	A - Grant	$0.00	+45.0K	82.5K	+120%	$0
D	2026-02-24	2026-02-24	CRBU	Kelly Timothy P	CTO	S - Sale	$1.96	-3,147	79.4K	-4%	-$6,168
D	2026-02-24	2026-02-20	CRBU	Kelly Timothy P	CTO	A - Grant	$0.00	+202.5K	202.5K	New	$0

Purchase Sale Sale after option exercise All abbreviations

#	Table	Security	Date	Code	A/D	Shares	Price	Owned after	Own	Exercise / expiry	Underlying	Footnotes
1	Common	Common Stock	2026-02-20	A	A	45,000	$0.00	82,500	D	—	—	(F1) This reflects restricted stock units ("RSUs") that vest in four equal annual installments beginning on February 20, 2027, subject to the reporting person continuing to provide service to the Issuer through the applicable vesting dates. The RSUs will be settled in stock within 30 days after each vesting date.
2	Common	Common Stock	2026-02-24	S	D	3,147	$1.96	79,353	D	—	—	(F2) Reflects the number of shares of common stock that were sold pursuant to the Issuer's mandatory sell-to-cover policy for the sole purpose of satisfying tax withholding obligations in connection with the vesting of RSUs previously granted to the reporting person and does not represent a discretionary trade by the reporting person.
3	Derivative	Option to purchase Common Stock	2026-02-20	A	A	202,500	$0.00	202,500	D	$1.80 · — to 2036-02-19	202,500 Common Stock	(F3) 1/48 of the total number of shares subject to this option will vest on each monthly anniversary of the grant date such that the option will be fully vested on February 20, 2030, subject to the reporting person continuing to provide service to the Issuer through each such vesting date.