Sec Form 4 Filing - FORMELA JEAN FRANCOIS @ 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 FORMELA JEAN FRANCOIS 2. Issuer Name and Ticker or Trading Symbol Korro Bio, Inc. [ KRRO] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (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 Common Stock 11/03/2023 A( 1 )( 2 ) 942,075 ( 1 ) ( 2 ) A 942,075 I See Footnote ( 3 ) Common Stock 11/03/2023 A( 4 ) 177,217 ( 4 ) A 177,217 I See Footnote ( 5 )

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) $ 14.98 11/03/2023 A 16,000 ( 6 ) 11/02/2033 Common Stock 16,000 $ 0 16,000 D ( 7 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other FORMELA JEAN FRANCOIS C/O KORRO BIO, INC. ONE KENDALL SQUARE, BUILDING 600-700 CAMBRIDGE, MA02139 X Signatures /s/ Ommer Chohan, Attorney-in-fact 11/07/2023 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Received in exchange for (i) 3,000,000 shares of common stock, (ii) 4,000,000 shares of Series Seed 1 Preferred Stock, (iii) 2,000,000 shares of Series Seed 2 Preferred Stock, (iv) 1,538,462 shares of Series Seed 3 Preferred Stock, (v) 5,357,142 shares of Series A Preferred Stock and (vi) 3,064,273 shares of Series B Preferred Stock of Korro Bio Ops, Inc. (f/k/a Korro Bio, Inc., "Legacy Korro") pursuant to an Agreement and Plan of Merger dated as of July 14, 2023 (the "Merger Agreement") by and among Legacy Korro, the Issuer (f/k/a Frequency Therapeutics, Inc.) and Frequency Merger Sub, Inc., a wholly owned subsidiary of the Issuer ("Merger Sub"). Under the terms of the Merger Agreement, 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. ( 2 )(Continued from Footnote 1) Upon the closing of the Merger, each share of Legacy Korro common stock was converted into the right to receive 0.049688 of a share of the Issuer's common stock, after giving effect to a reverse stock split of the Issuer's common stock of 1-for-50. Subsequent to the Merger, the name of the Issuer was changed from Frequency Therapeutics, Inc. to Korro Bio, Inc. ( 3 )These shares are held directly by Atlas Venture Fund XI, L.P. ("Atlas XI"). Atlas Venture Associates XI, L.P. ("Associates XI") is the general partner of Atlas XI. Atlas Venture Associates XI, LLC ("Associates XI LLC") is the general partner of Associates XI. The Reporting Person is a member of Associates XI LLC and disclaims Section 16 beneficial ownership of such shares, except to the extent of his pecuniary interest therein, if any. ( 4 )Received in exchange for Legacy Korro common stock issued in the private placement completed immediately prior to the Merger. ( 5 )These shares are held directly by Atlas Venture Opportunity Fund II, L.P. ("Atlas Opportunity II"). Atlas Venture Associates Opportunity II, L.P. ("Associates II") is the general partner of Atlas Opportunity II. Atlas Venture Associates Opportunity II, LLC ("Associates II LLC") is the general partner of Associates II. The Reporting Person is a member of Associates II LLC and disclaims Section 16 beneficial ownership of such shares, except to the extent of his pecuniary interest therein, if any. ( 6 )The shares subject to the option vest in three equal annual installments commencing from November 3, 2023, subject to the Reporting Person's continued service on each such vesting date. ( 7 )The Reporting Person is a member of Atlas XI and is obligated to transfer the economic benefit, if any, received upon the sale of the shares issuable upon exercise of the option to Atlas Venture Life Science Advisors, LLC. As such, the Reporting Person disclaims beneficial ownership of the securities reported herein, except to the extent of his pecuniary interest therein, if any.

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