Generation Bio (GBIO) director McDonough reports RSU vesting and share sale

Rhea-AI Filing Summary

Generation Bio Co. director Geoff McDonough reported equity activity tied to restricted stock units on February 2, 2026. A total of 1,582 restricted stock units vested and converted into the same number of common shares at an exercise price of $0, increasing his direct common stock holdings.

To cover tax obligations from this vesting, 550 common shares were disposed of at $5.64 per share, leaving McDonough with 138,492 common shares held directly. He also has indirect beneficial ownership of 22,646 shares through the McDonough Family 2018 Irrevocable Trust and 27,500 shares through the McDonough Family 2020 Irrevocable Trust.

The vested units come from a grant of 8,437 restricted stock units awarded on January 20, 2023, which became fully vested on February 2, 2026 under the terms of a merger agreement among Generation Bio, XOMA Royalty Corporation and a subsidiary.

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

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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)
02/02/2026

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	02/02/2026		M		1,582	A	(1)	139,042	D
Common Stock	02/02/2026		F		550	D	$5.64	138,492	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)	02/02/2026		M			1,582	(4)	(4)	Common Stock	1,582	$0	0	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. 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.

	/s/ Shawna-Gay White, Attorney-in-Fact	02/04/2026
	** Signature of Reporting Person	Date
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FAQ

What insider transactions did Geoff McDonough report for GBIO on February 2, 2026?

Geoff McDonough reported the vesting of 1,582 restricted stock units into common shares and the disposition of 550 shares at $5.64 each. After these transactions, he directly held 138,492 Generation Bio Co. common shares, plus additional indirect holdings through family trusts.

How many Generation Bio (GBIO) shares does Geoff McDonough own after this Form 4?

After the reported transactions, Geoff McDonough directly owns 138,492 Generation Bio common shares. He is also deemed to beneficially own 22,646 shares via the McDonough Family 2018 Irrevocable Trust and 27,500 shares via the McDonough Family 2020 Irrevocable Trust, reflecting additional indirect interests.

What triggered the vesting of Geoff McDonough’s restricted stock units at Generation Bio?

The vesting was triggered under a merger agreement among Generation Bio, XOMA Royalty Corporation and a subsidiary. That agreement provided that each outstanding unvested restricted stock unit became fully vested on February 2, 2026, causing 1,582 units from an earlier 8,437-unit grant to convert into common shares.

Why were 550 Generation Bio shares sold or withheld at $5.64 on this Form 4?

The 550 shares at $5.64 were disposed of in connection with the restricted stock unit vesting, typically to satisfy tax withholding obligations. This transaction reduced the newly issued shares from the vesting, leaving Geoff McDonough with 138,492 common shares held directly after the Form 4 transactions.

What are the McDonough Family 2018 and 2020 Trusts’ holdings in Generation Bio (GBIO)?

The McDonough Family 2018 Irrevocable Trust holds 22,646 Generation Bio common shares, and the McDonough Family 2020 Irrevocable Trust holds 27,500 shares. Geoff McDonough is the settlor of both trusts and may be deemed to beneficially own the shares those trusts hold, according to the filing’s footnotes.