Atlas Venture Fund X, L.P. - 09 Feb 2026 Form 4 Insider Report for Generation Bio Co. (GBIO)

Reporting relationship: 10%+ Owner
Issuer ticker: GBIO
Reported as of: 09 Feb 2026
Net transaction value: $0
SEC form: 4
Accepted by SEC: 09 Feb 2026, 18:19:16 UTC
Prior SEC filing: 27 Mar 2024
Source filing: View source filing
Reporting owner signature: 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

Filing notes and source

Key filing fact

Atlas Venture Fund X, L.P. filed Form 4 for Generation Bio Co. (GBIO) on 09 Feb 2026.

Key facts

This page summarizes Atlas Venture Fund X, L.P.'s Form 4 filing for Generation Bio Co. (GBIO).
3 reported transactions and 0 derivative rows are listed below.
Accepted by SEC: 09 Feb 2026, 18:19.

Change

Previous filing in this sequence was filed on 27 Mar 2024.
Current net transaction value: $0.

Research use

This tells you what this filing adds before you inspect full transaction and derivative tables.
You can trace every row back to the original SEC filing document.

Evidence

Filed on Form 4

Ownership activity is grounded in SEC Form 4 disclosures.

View source filing

Reporting Owners (6)

CIK 0001628098 Primary reporting owner

Atlas Venture Fund X, L.P.

Relationship: 10%+ Owner
Address: 300 TECHNOLOGY SQUARE, 8TH FLOOR, CAMBRIDGE
Signature: 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
Signature date: 09 Feb 2026

CIK 0001742766

ATLAS VENTURE ASSOCIATES X, L.P.

Relationship: 10%+ Owner
Address: 300 TECHNOLOGY SQUARE, 8TH FLOOR, CAMBRIDGE
Signature: Atlas Venture Associates X, L.P., By: Atlas Venture Associates X, LLC, Its: General Partner, By: /s/ Ommer Chohan, Chief Financial Officer
Signature date: 09 Feb 2026

CIK 0001742765

Atlas Venture Associates X, LLC

Relationship: 10%+ Owner
Address: 300 TECHNOLOGY SQUARE, 8TH FLOOR, CAMBRIDGE
Signature: Atlas Venture Associates X, LLC, By: /s/ Ommer Chohan, Chief Financial Officer
Signature date: 09 Feb 2026

CIK 0001759241

Atlas Venture Opportunity Fund I, L.P.

Relationship: 10%+ Owner
Address: 300 TECHNOLOGY SQUARE, 8TH FLOOR, CAMBRIDGE
Signature: 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
Signature date: 09 Feb 2026

CIK 0001780065

Atlas Venture Associates Opportunity I, L.P.

Relationship: 10%+ Owner
Address: 300 TECHNOLOGY SQUARE, 8TH FLOOR, CAMBRIDGE
Signature: Atlas Venture Associates Opportunity I, L.P., By: Atlas Venture Associates Opportunity I, LLC, Its general partner, By: /s/ Ommer Chohan, Chief Financial Officer
Signature date: 09 Feb 2026

CIK 0001780066

Atlas Venture Associates Opportunity I, LLC

Relationship: 10%+ Owner
Address: 300 TECHNOLOGY SQUARE, 8TH FLOOR, CAMBRIDGE
Signature: Atlas Venture Associates Opportunity I, LLC, By: /s/ Ommer Chohan, Chief Financial Officer
Signature date: 09 Feb 2026

Reported non-derivative transactions

Shares, units, or other non-derivative securities reported in this filing.

GBIO transaction

Common Stock

Disposition pursuant to a tender of shares in a change of control transaction

Transaction value
Shares: -711,193
Change %: -100%
Price
Shares after: 0
Date: 09 Feb 2026
Ownership: Direct
Footnotes: F1, F2, F3

GBIO transaction

Common Stock

Disposition pursuant to a tender of shares in a change of control transaction

Transaction value
Shares: -116,693
Change %: -100%
Price
Shares after: 0
Date: 09 Feb 2026
Ownership: See footnote
Footnotes: F1, F2, F4

GBIO transaction

Common Stock

Disposition pursuant to a tender of shares in a change of control transaction

Transaction value
Shares: -60
Change %: -100%
Price
Shares after: 0
Date: 09 Feb 2026
Ownership: See footnote
Footnotes: F1, F2, F5

^* marks a reported price that did not pass the local price check.

Additional SEC filing notes

Filing notes and footnotes

Section 16 status

Atlas Venture Fund X, L.P. is no longer subject to Section 16 filing requirements. Form 4 or Form 5 obligations may still apply in specific circumstances.

Explanation of responses 5 footnotes

Footnote F1

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"),

Footnote F2

(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.

Footnote F3

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.

Footnote F4

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.

Footnote F5

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.