Sec Form 4 Filing - Chappell Todd @ Korro Bio, Inc. - 2023-11-03

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

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, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person Chappell Todd 2. Issuer Name and Ticker or Trading Symbol Korro Bio, Inc. [ KRRO] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) Chief Operating Officer (Last) (First) (Middle) C/O KORRO BIO, INC., ONE KENDALL SQUARE, BUILDING 600-700 3. Date of Earliest Transaction (MM/DD/YY) 11/03/2023 (Street) CAMBRIDGE, MA02139 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 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

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 (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 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 (MM/DD/YY) 7. Title and Amount of Underlying Securities (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 of Derivative Security: 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 Stock Option (Right to Buy) $ 11.68 ( 1 ) ( 2 ) 11/03/2023 A( 1 )( 2 ) 13,625 ( 1 ) ( 2 ) ( 3 ) 03/09/2031 Common Stock 13,625 ( 1 ) ( 2 ) ( 1 ) ( 2 ) ( 4 ) 13,625 D Stock Option (Right to Buy) $ 22.75 ( 1 ) ( 2 ) 11/03/2023 A( 1 )( 2 ) 4,968 ( 1 ) ( 2 ) ( 5 ) 01/26/2032 Common Stock 4,968 ( 1 ) ( 2 ) ( 1 ) ( 2 ) ( 6 ) 4,968 D Stock Option (Right to Buy) $ 20.94 ( 1 ) ( 2 ) 11/03/2023 A( 1 )( 2 ) 5,128 ( 1 ) ( 2 ) ( 7 ) 01/23/2033 Common Stock 5,128 ( 1 ) ( 2 ) ( 1 ) ( 2 ) ( 8 ) 5,128 D Stock Option (Right to Buy) $ 14.98 11/03/2023 A 62,651 ( 9 ) 11/02/2033 Common Stock 62,651 $ 0 62,651 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Chappell Todd C/O KORRO BIO, INC. ONE KENDALL SQUARE, BUILDING 600-700 CAMBRIDGE, MA02139 Chief Operating Officer Signatures /s/ Shelby Walker, Attorney-in-fact 11/07/2023 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Under the terms of an Agreement and Plan of Merger dated as of July 14, 2023 by and among Korro Bio Ops, Inc. (f/k/a Korro Bio, Inc., "Legacy Korro"), the Issuer (f/k/a Frequency Therapeutics, Inc.) and Frequency Merger Sub, Inc., a wholly owned subsidiary of the Issuer ("Merger Sub"), on November 3, 2023, Merger Sub merged with and into Legacy Korro (the "Merger"), with Legacy Korro surviving the Merger as a wholly owned subsidiary of the Issuer. Upon the closing of the Merger, each outstanding option to purchase shares of Legacy Korro common stock issued under the Korro Bio, Inc. 2019 Stock Incentive Plan (the "2019 Plan") was assumed by the Issuer and converted into an option to purchase the Issuer's common stock, at an exchange ratio of 0.049688 per share, on the same terms and conditions as were applicable under the 2019 Plan prior to the Merger, after giving effect to a reverse stock split of the Issuer's common stock of 1-for-50. ( 2 )(Continued from footnote 1) Subsequent to the Merger, the name of the Issuer was changed from Frequency Therapeutics, Inc. to Korro Bio, Inc. ( 3 )The shares subject to the option vest as to 25% of the shares on March 8, 2022, with the remainder vesting in 36 equal monthly installments thereafter, subject to the Reporting Person's continued service on each such vesting date. ( 4 )Received in exchange for a stock option to acquire 274,220 shares of Legacy Korro common stock issued under the 2019 Plan pursuant to the Merger Agreement. ( 5 )The shares subject to the option vest as to 25% of the shares on January 27, 2023, with the remainder vesting in 36 equal monthly installments thereafter, subject to the Reporting Person's continued service on each such vesting date. ( 6 )Received in exchange for a stock option to acquire 100,000 shares of Legacy Korro common stock issued under the 2019 Plan pursuant to the Merger Agreement. ( 7 )The shares subject to the option vest as to 25% of the shares on January 1, 2024, with the remainder vesting in 36 equal monthly installments thereafter, subject to the Reporting Person's continued service on each such vesting date. ( 8 )Received in exchange for a stock option to acquire 103,223 shares of Legacy Korro common stock issued under the 2019 Plan pursuant to the Merger Agreement. ( 9 )The shares subject to the option vest in 48 equal monthly installments commencing from November 3, 2023, subject to the Reporting Person's continued service on each such vesting 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).

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