Generation Bio (GBIO) director reports RSU vesting and share withholding

Rhea-AI Filing Summary

Generation Bio Co. director Geoff McDonough reported changes in his holdings of the company’s common stock on January 15, 2026. A block of 395 restricted stock units converted into the same number of common shares, reflecting previously granted equity that is now vested.

To cover taxes on this vesting, 137 common shares were withheld at a price of $5.64 per share. After these transactions, McDonough directly holds 137,460 common shares, with additional indirect holdings of 22,646 shares through the McDonough Family 2018 Irrevocable Trust and 27,500 shares through the McDonough Family 2020 Irrevocable Trust.

Insider Trade Summary

395 shares exercised/converted

Mixed 5 txns

Insider MCDONOUGH GEOFF

Role Director

Type	Security	Shares	Price	Value
Exercise	Restricted Stock Units	395	$0.00	--
Exercise	Common Stock	395	$0.00	--
Tax Withholding	Common Stock	137	$5.64	$772.68
holding	Common Stock	--	--	--
holding	Common Stock	--	--	--

Holdings After Transaction: Restricted Stock Units — 1,582 shares (Direct); Common Stock — 137,597 shares (Direct); Common Stock — 22,646 shares (Indirect, By 2018 Trust)

Footnotes (1)

1. Each restricted stock unit represents the right to receive one share of the company's common stock. 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. 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. On January 20, 2023, the reporting person was granted 8,437 restricted stock units. The shares underlying the restricted stock units vest over two years, with 25% of the shares vesting on July 15, 2022 and the remaining shares vesting in equal quarterly installments thereafter.

Form 4 Insider Transactions: What Each Field Means →

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

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 for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

MCDONOUGH GEOFF

(Last) (First) (Middle)

C/O GENERATION BIO CO., 301 BINNEY ST

(Street)

CAMBRIDGE MA 02142

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
Generation Bio Co. [ GBIO ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

3. Date of Earliest Transaction (Month/Day/Year)
01/15/2026

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

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	01/15/2026		M		395	A	(1)	137,597	D
Common Stock	01/15/2026		F		137	D	$5.64	137,460	D
Common Stock								22,646	I	By 2018 Trust(2)
Common Stock								27,500	I	By 2020 Trust(3)

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 Securities Underlying Derivative Security (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: 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
Restricted Stock Units	(1)	01/15/2026		M		395		(4)	(4)	Common Stock	395	$0	1,582	D

Explanation of Responses:

1. Each restricted stock unit represents the right to receive one share of the company's common stock.

2. 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.

3. 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.

4. On January 20, 2023, the reporting person was granted 8,437 restricted stock units. The shares underlying the restricted stock units vest over two years, with 25% of the shares vesting on July 15, 2022 and the remaining shares vesting in equal quarterly installments thereafter.

	/s/ Shawna-Gay White, Attorney-in-Fact	01/16/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* 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).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.

FAQ

What insider transaction did GBIO director Geoff McDonough report?

Geoff McDonough reported the conversion of 395 restricted stock units into the same number of Generation Bio Co. common shares on January 15, 2026, along with related tax withholding.

How many Generation Bio (GBIO) shares were withheld for taxes in this Form 4?

To satisfy tax obligations related to the vesting, 137 common shares of Generation Bio Co. were disposed of at a price of $5.64 per share.

How many GBIO shares does Geoff McDonough directly own after this transaction?

Following the reported transactions, Geoff McDonough directly owns 137,460 shares of Generation Bio Co. common stock.

What indirect Generation Bio (GBIO) holdings are reported for Geoff McDonough?

Indirect holdings include 22,646 common shares held by the McDonough Family 2018 Irrevocable Trust and 27,500 common shares held by the McDonough Family 2020 Irrevocable Trust.

What are the restricted stock units mentioned in the GBIO Form 4?

Each restricted stock unit represents the right to receive one share of Generation Bio Co. common stock, subject to the vesting schedule described in the prior grant.

When were the Generation Bio (GBIO) restricted stock units originally granted to Geoff McDonough?

The filing notes that on January 20, 2023, McDonough was granted 8,437 restricted stock units, which vest over two years under the grant’s schedule.