Caribou Biosciences (CRBU) CLO awarded major equity grants, sells shares for taxes

Rhea-AI Filing Summary

Caribou Biosciences Chief Legal Officer Barbara G. McClung reported both equity grants and a small share sale. She received a grant of options to purchase 202,500 shares of common stock and a separate grant of 45,000 restricted stock units, both awarded on February 20, 2026.

The options vest in equal monthly installments over 48 months until February 20, 2030, and the RSUs vest in four equal annual installments beginning February 20, 2027, contingent on continued service. On February 24, 2026, 6,938 shares were sold at $1.96 per share solely to cover tax withholding on previously vested RSUs under an existing Rule 10b5-1 sell-to-cover plan, leaving her with 481,564 common shares directly owned.

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
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Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

MCCLUNG BARBARA G

(Last) (First) (Middle)

C/O CARIBOU BIOSCIENCES, INC.

2929 7TH STREET, SUITE 105

(Street)

BERKELEY CA 94710

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
Caribou Biosciences, Inc. [ CRBU ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	Chief Legal Officer

3. Date of Earliest Transaction (Month/Day/Year)
02/20/2026

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	02/20/2026		A		45,000(1)	A	$0	488,502	D
Common Stock	02/24/2026		S(2)		6,938(2)	D	$1.96	481,564	D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Option to purchase Common Stock	$1.8	02/20/2026		A		202,500		(3)	02/19/2036	Common Stock	202,500	$0	202,500	D

Explanation of Responses:

1. 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. Reflects the number of shares of common stock that were sold in a "sell-to-cover" transaction 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. This transaction was made pursuant to a Rule 10b5-1 trading plan in the form of a durable sell-to-cover instruction adopted prior to the 2023 amendments to Rule 10b5-1. The trading plan provides for the automatic sale of shares of common stock necessary to satisfy the reporting person's tax withholding obligations incurred in connection with the vesting of RSUs.

3. 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.

Remarks:

	/s/ Barbara G. McClung	02/24/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.

FAQ

What equity awards did Caribou Biosciences (CRBU) grant to Barbara McClung?

Barbara McClung received options for 202,500 shares and 45,000 restricted stock units. The options were granted at a $0.00 exercise price and vest monthly over 48 months, while the RSUs vest in four equal annual installments starting February 20, 2027.

How do Barbara McClung’s new stock options at Caribou Biosciences (CRBU) vest?

The 202,500 stock options vest in 48 equal monthly installments. One forty-eighth of the total vests on each monthly anniversary of the February 20, 2026 grant date, so the option becomes fully vested on February 20, 2030, assuming continued service to Caribou Biosciences.

What are the vesting terms of Barbara McClung’s RSUs at Caribou Biosciences (CRBU)?

The 45,000 RSUs vest in four equal annual installments beginning February 20, 2027. Vesting requires that Barbara McClung continue providing service to Caribou Biosciences on each vesting date, and the RSUs settle in stock within 30 days after each vesting date.

Why did Barbara McClung sell Caribou Biosciences (CRBU) shares in February 2026?

She sold 6,938 shares at $1.96 solely to cover tax withholding from previously vested RSUs. The transaction was automatic under a pre-existing Rule 10b5-1 durable sell-to-cover plan, and was not a discretionary trade in Caribou Biosciences stock by her.

How many Caribou Biosciences (CRBU) shares does Barbara McClung own after these transactions?

Following the February 24, 2026 sell-to-cover transaction, Barbara McClung directly owns 481,564 shares of Caribou Biosciences common stock. This figure reflects her holdings after selling 6,938 shares to satisfy tax obligations tied to earlier RSU vesting.