Generation Bio Co. — Director's Dealing 2026

Feb 9, 2026

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: Generation Bio Co. (GBIO)
CIK: 0001733294
Period of Report: 2026-02-09

Reporting Person: Christensen Gustav (Director)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2026-02-09	Common Stock	U	13142	—	Disposed	0	Direct

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2026-02-09	Stock Option (right to buy)	$3.874	D	3000	Disposed		Common Stock (3000)	Direct
2026-02-09	Stock Option (right to buy)	$190.00	D	5200	Disposed		Common Stock (5200)	Direct
2026-02-09	Stock Option (right to buy)	$265.90	D	1500	Disposed		Common Stock (1500)	Direct
2026-02-09	Stock Option (right to buy)	$61.90	D	1920	Disposed		Common Stock (1920)	Direct
2026-02-09	Stock Option (right to buy)	$48.30	D	2500	Disposed		Common Stock (2500)	Direct
2026-02-09	Stock Option (right to buy)	$33.20	D	6000	Disposed		Common Stock (6000)	Direct

Footnotes

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"),

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.

F3: Pursuant to the terms of the Merger Agreement, effective as of immediately prior to the Effective Time, each option to purchase shares of Common Stock ("Issuer Option") that was outstanding and unexercised as of immediately prior to the Effective Time and had an exercise price per Share that was less than the Cash Amount (each, an "In-The-Money Option"), became fully vested and was automatically cancelled and converted into the right to receive an amount in cash, without interest, equal to the product obtained by multiplying (x) the excess of the Cash Amount over the exercise price per share of Common Stock underlying such In-the-Money Option at the Effective Time by (y) the number of shares of Common Stock underlying such In-the-Money Option at the Effective Time.

F4: Pursuant to the terms of the Merger Agreement, effective as of immediately prior to the Effective Time, each Issuer Option that was outstanding and unexercised as of immediately prior to the Effective Time and had an exercise price per Share that was equal to or greater than the Cash Amount was automatically cancelled for no consideration.