Caribou Biosciences (CRBU) CBO awarded stock options, sells shares for tax

Rhea-AI Filing Summary

Caribou Biosciences Chief Business Officer Ruhi Ahmad Khan reported a mix of equity grants and a small tax-related share sale. On February 24, 2026, Khan sold 6,938 shares of common stock at $1.96 per share in an open-market transaction, leaving 104,998 shares held directly. A footnote explains this was a sell-to-cover trade executed under a Rule 10b5-1 plan solely to satisfy tax withholding on vesting RSUs, not a discretionary sale.

On February 20, 2026, Khan received a grant of 45,000 restricted stock units that vest in four equal annual installments beginning on February 20, 2027, with shares delivered within 30 days after each vesting date. On the same date, Khan was granted options for 202,500 shares of common stock, vesting monthly over 48 months so that the option is fully vested by February 20, 2030, contingent on continued service.

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

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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^*

Khan Ruhi Ahmad

(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 Business 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	111,936	D
Common Stock	02/24/2026		S(2)		6,938(2)	D	$1.96	104,998	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, as attorney-in-fact	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).
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FAQ

What insider transactions did Caribou Biosciences (CRBU) report for Ruhi Ahmad Khan?

Caribou Biosciences reported that Chief Business Officer Ruhi Ahmad Khan received new stock options and RSUs and completed a small share sale. The sale was tied to tax withholding for vesting RSUs and executed under a pre-established Rule 10b5-1 trading plan.

How many Caribou Biosciences (CRBU) shares did Ruhi Ahmad Khan sell and at what price?

Ruhi Ahmad Khan sold 6,938 shares of Caribou Biosciences common stock at $1.96 per share. According to the filing, this transaction was a sell-to-cover trade executed solely to meet tax withholding obligations arising from previously granted RSUs.

What equity awards did Ruhi Ahmad Khan receive from Caribou Biosciences (CRBU)?

Ruhi Ahmad Khan received options for 202,500 shares of Caribou Biosciences common stock and 45,000 restricted stock units. The options vest monthly over 48 months, and the RSUs vest in four equal annual installments starting in February 2027, subject to continued service.

When do Ruhi Ahmad Khan’s new Caribou Biosciences (CRBU) RSUs vest?

The 45,000 RSUs granted to Ruhi Ahmad Khan vest in four equal annual installments beginning on February 20, 2027. Shares underlying the RSUs will be delivered within 30 days after each vesting date, assuming continued service to Caribou Biosciences.

What are the vesting terms of Ruhi Ahmad Khan’s Caribou Biosciences (CRBU) stock options?

The options for 202,500 Caribou Biosciences shares vest over 48 months, with 1/48 of the total vesting each month. The option will be fully vested by February 20, 2030, provided Ruhi Ahmad Khan continues to provide service through each vesting date.

Was Ruhi Ahmad Khan’s Caribou Biosciences (CRBU) share sale discretionary?

The filing states the 6,938-share sale was not discretionary. It was a sell-to-cover transaction under a Rule 10b5-1 durable instruction, executed solely to satisfy tax withholding obligations from the vesting of previously granted RSUs.