Washington, D.C. 20549


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 Number: 3235-0287
Estimated average burden
hours per response: 0.5
Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).
1. Name and Address of Reporting Person*
Haurwitz Rachel E.

(Last) (First) (Middle)
2929 7TH STREET, SUITE 105


(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)
X Director 10% Owner
X Officer (give title below) Other (specify below)
President and CEO
3. Date of Earliest Transaction (Month/Day/Year)
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 01/26/2022 M 10,000 A $2.96(1) 10,000(2) D
Common Stock 3,349,395(2) I by Trust(3)
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 $2.96(1) 01/26/2022 M 10,000 (4) 06/11/2023 Common Stock 10,000 $0.00 126,350 D
Explanation of Responses:
1. Due to a rounding error, the exercise price for this stock option was inadvertently originally reported as $2.95 per share on the reporting person's Form 3 filed on July 22, 2021.
2. This Form 4/A is being filed to correct an inadvertent error in the original Form 4 filed January 27, 2022 attributing direct ownership of 3,349,395 shares listed in column 5 to the reporting person. As described in a Form 5 filed on February 9, 2022, on September 27, 2021, these 3,349,395 shares were transferred to a trust for which the reporting person and her spouse serve as a Co-Trustees.
3. Shares are held by The City Canyon Trust Dated May 31, 2021, of which the reporting person is a Co-Trustee with her spouse.
4. 1/4th of the shares subject to this option vested on June 12, 2019 and an additional 1/48th of the aggregate number of shares subject to this option have vested or will vest on the corresponding day of each month thereafter until the option is fully vested on June 12, 2022, subject to the reporting person's continued service to the Issuer through the applicable vesting dates.
/s/ Barbara G. McClung, at attorney-in-fact 05/10/2022
** 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.