Yalonda Howze - Oct 15, 2025 Form 4 Insider Report for Generation Bio Co. (GBIO)

Role: CHIEF LEGAL OFFICER
Signature: /s/ Shawna-Gay White, Attorney-in-Fact
Stock symbol: GBIO
Transactions as of: Oct 15, 2025
Transactions value $: -$664
Form type: 4
Date filed: 10/17/2025, 04:05 PM
Previous filing: Jul 17, 2025
SEC: View on sec.gov

Reporting Owners (1)

Name	Relationship	Address	Signature	Signature date	CIK
Howze Yalonda	CHIEF LEGAL OFFICER	C/O GENERATION BIO CO., 301 BINNEY STREET, SUITE 401, CAMBRIDGE	/s/ Shawna-Gay White, Attorney-in-Fact	2025-10-17	0001828153

Transactions Table

Type	Sym	Class	Transaction	Value $	Shares	Change %	* Price $	Shares After	Date	Ownership	Footnotes
transaction	GBIO	Common Stock	Options Exercise		+334	+15.83%		2.44K	Oct 15, 2025	Direct	F1, F2
transaction	GBIO	Common Stock	Tax liability	-$664	-99	-4.05%	$6.71	2.35K	Oct 15, 2025	Direct	F1

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	-334	-14.26%	$0.00	2.01K	Oct 15, 2025	Common Stock	334		Direct	F1, F2, F3

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

Explanation of Responses:

Id	Content
F1	Amounts reported in this Form 4 reflect the one-for-10 reverse stock split effected by the issuer on July 21, 2025.
F2	Each restricted stock unit represents the right to receive one share of the company's common stock.
F3	The grant of 5,355 restricted stock units was made on April 5, 2023. The shares underlying the restricted stock units vest over four years, with 25% of the shares vested on April 15, 2024 and the remaining shares vesting in equal quarterly installments thereafter.