Geoff Mcdonough - 02 Feb 2026 Form 4 Insider Report for Generation Bio Co. (GBIO)

Role: Director
Signature: /s/ Shawna-Gay White, Attorney-in-Fact
Issuer symbol: GBIO
Transactions as of: 02 Feb 2026
Net transactions value: -$3,102
Form type: 4
Filing time: 04 Feb 2026, 16:05:27 UTC
Previous filing: 16 Jan 2026
Next filing: 09 Feb 2026
SEC: View on sec.gov

Reporting Owners (1)

Name	Relationship	Address	Signature	Signature date	CIK
MCDONOUGH GEOFF	Director	C/O GENERATION BIO CO., 301 BINNEY ST, CAMBRIDGE	/s/ Shawna-Gay White, Attorney-in-Fact	04 Feb 2026	0001732701

Transactions Table

Type	Sym	Class	Transaction	Value $	Shares	Change %	* Price $	Shares After	Date	Ownership	Footnotes
transaction	GBIO	Common Stock	Options Exercise		+1,582	+1.2%		139,042	02 Feb 2026	Direct	F1
transaction	GBIO	Common Stock	Tax liability	$3,102	-550	-0.4%	$5.64	138,492	02 Feb 2026	Direct
holding	GBIO	Common Stock						22,646	02 Feb 2026	By 2018 Trust	F2
holding	GBIO	Common Stock						27,500	02 Feb 2026	By 2020 Trust	F3

Derivative Securities (e.g., puts, calls, warrants, options, convertible securities)

Type	Sym	Class	Transaction	Value $	Shares	Change %	* Price $	Shares After	Date	Underlying Class	Amount	Exercise Price	Ownership	Footnotes
transaction	GBIO	Restricted Stock Units	Options Exercise	$0	-1,582	-100%	$0.000000	0	02 Feb 2026	Common Stock	1,582		Direct	F1, F4

* An asterisk sign (*) next to the price indicates that the price is likely invalid.

Explanation of Responses:

Id	Content
F1	Each restricted stock unit represents the right to receive one share of the company's common stock.
F2	The securities are directly held by the McDonough Family 2018 Irrevocable Trust, or the 2018 Trust. The reporting person is the settlor of the 2018 Trust, Allison L. McDonough and David S. Grayzel are trustees for the 2018 Trust, and the 2018 Trust is for the benefit of Graeme and Owen McDonough. The reporting person may be deemed to beneficially own the shares of common stock owned by the 2018 Trust.
F3	The securities are directly held by the McDonough Family 2020 Irrevocable Trust, or the 2020 Trust. The reporting person is the settlor of the 2020 Trust, Allison L. McDonough and David S. Grayzel are trustees for the 2020 Trust, and the 2020 Trust is for the benefit of Allison, Graeme and Owen McDonough. The reporting person may be deemed to beneficially own the shares of common stock owned by the 2020 Trust.
F4	On January 20, 2023, the reporting person was granted 8,437 restricted stock units. Pursuant to the terms of that certain Agreement and Plan of Merger, by and among the Issuer, XOMA Royalty Corporation ("Parent") and Parent's wholly-owned subsidiary, XRA 7 Corp., dated as of December 15, 2025 (the "Merger Agreement"), prior to the effective time of the merger as contemplated by the Merger Agreement, each restricted stock unit of the Issuer that was outstanding and unvested became vested in full on February 2, 2026.