Statement of Changes in Beneficial Ownership (Form 4)

FORM 4 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 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person * Atlas Venture Fund X, L.P. 2. Issuer Name and Ticker or Trading Symbol Generation Bio Co. [GBIO] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director __X__ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 300 TECHNOLOGY SQUARE, 8TH FLOOR 3. Date of Earliest Transaction (Month/Day/Year) 02/09/2026 (Street) CAMBRIDGE, MA 02139 4. If Amendment, Date Original Filed (Month/Day/Year) 6. Individual or Joint/Group Filing (Check Applicable Line) ___ Form filed by One Reporting Person _X_ 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 (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 02/09/2026 U(1)(2) 711,193 D (1)(2) 0 D(3) Common Stock 02/09/2026 U(1)(2) 116,693 D (1)(2) 0 I See footnote(4) Common Stock 02/09/2026 U(1)(2) 60 D (1)(2) 0 I See footnote(5)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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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 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

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Atlas Venture Fund X, L.P. 300 TECHNOLOGY SQUARE, 8TH FLOOR CAMBRIDGE, MA 02139		X
ATLAS VENTURE ASSOCIATES X, L.P. 300 TECHNOLOGY SQUARE, 8TH FLOOR CAMBRIDGE, MA 02139		X
Atlas Venture Associates X, LLC 300 TECHNOLOGY SQUARE, 8TH FLOOR CAMBRIDGE, MA 02139		X
Atlas Venture Opportunity Fund I, L.P. 300 TECHNOLOGY SQUARE, 8TH FLOOR CAMBRIDGE, MA 02139		X
Atlas Venture Associates Opportunity I, L.P. 300 TECHNOLOGY SQUARE, 8TH FLOOR CAMBRIDGE, MA 02139		X
Atlas Venture Associates Opportunity I, LLC 300 TECHNOLOGY SQUARE, 8TH FLOOR CAMBRIDGE, MA 02139		X

Signatures

Atlas Venture Fund X, L.P., By: Atlas Venture Associates X, L.P., Its: General Partner, By: Atlas Venture Associates X, LLC, Its: General Partner, By: /s/ Ommer Chohan, Chief Financial Officer		02/09/2026
**Signature of Reporting Person		Date
Atlas Venture Associates X, L.P., By: Atlas Venture Associates X, LLC, Its: General Partner, By: /s/ Ommer Chohan, Chief Financial Officer		02/09/2026
**Signature of Reporting Person		Date
Atlas Venture Associates X, LLC, By: /s/ Ommer Chohan, Chief Financial Officer		02/09/2026
**Signature of Reporting Person		Date
Atlas Venture Opportunity Fund I, L.P., By: Atlas Venture Associates Opportunity I, L.P., Its general partner, By: Atlas Venture Associates Opportunity I, LLC, Its general partner, By: /s/ Ommer Chohan, Chief Financial Officer		02/09/2026
**Signature of Reporting Person		Date
Atlas Venture Associates Opportunity I, L.P., By: Atlas Venture Associates Opportunity I, LLC, Its general partner, By: /s/ Ommer Chohan, Chief Financial Officer		02/09/2026
**Signature of Reporting Person		Date
Atlas Venture Associates Opportunity I, LLC, By: /s/ Ommer Chohan, Chief Financial Officer		02/09/2026
**Signature of Reporting Person		Date

Explanation of Responses:

*	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).
(1)	Pursuant to the terms of that certain Agreement and Plan of Merger (the "Merger Agreement"), by and among Generation Bio. Co. (the "Issuer"), XOMA Royalty Corporation ("Parent") and Parent's wholly-owned subsidiary, XRA 7 Corp. ("Merger Sub"), dated as of December 15, 2025, the shares (the "Shares") of common stock, par value $0.0001 per share, of the Issuer (the "Common Stock") that were tendered to Merger Sub prior to the expiration time of the offer were exchanged for (i) a purchase price of $4.2913 per Share to the stockholders in cash, without interest and less any applicable tax withholding (the "Cash Amount"), plus (ii) one non-tradeable contingent value right per Share (the "CVR"),
(2)	(continued from footnote 1) which represents the right to receive certain contingent payments in cash in accordance with the terms and subject to the conditions of a contingent value rights agreement entered into by Parent and the rights agent, with an estimated maximum contingent consideration amount of $25.01 per CVR (the Cash Amount plus one CVR, collectively, the "Offer Price"). After completion of the tender offer, pursuant to the terms of the Merger Agreement, Merger Sub merged with and into the Issuer, effective as of February 9, 2026 (the "Effective Time"), with the Issuer continuing as the surviving corporation and a wholly owned subsidiary of Parent.
(3)	The shares are held directly by Atlas Venture Fund X, L.P. ("Atlas Venture Fund X"). The general partner of Atlas Venture Fund X is Atlas Venture Associates X, L.P. ("AVA X LP"). Atlas Venture Associates X, LLC ("AVA X LLC") is the general partner of AVA X LP. Each of AVA X LP and AVA X LLC disclaims Section 16 beneficial ownership of the securities held by Atlas Venture Fund X, except to the extent of its pecuniary interest therein, if any.
(4)	The shares are held directly by Atlas Venture Opportunity Fund I, L.P. ("Atlas Venture Opportunity Fund I"). The general partner of Atlas Venture Opportunity Fund I is Atlas Venture Associates Opportunity I, LP ("AVAO I LP"). Atlas Venture Associates Opportunity I, LLC ("AVAO I LLC") is the general partner of AVAO I LP. Each of AVAO I LP and AVAO I LLC disclaims Section 16 beneficial ownership of the securities held by Atlas Venture Opportunity Fund I, except to the extent of its pecuniary interest therein, if any.
(5)	The shares are held directly by AVAO I LP. AVAO I LLC is the general partner of AVAO I LP. AVAO I LLC disclaims Section 16 beneficial ownership of the securities held by AVAO I LP except to the extent of its pecuniary interest therein, if any.

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