[Form 4] Generation Bio Co. Insider Trading Activity

Rhea-AI Filing Summary

Generation Bio (GBIO) reported insider activity for its Chief Operating Officer on a Form 4. On 10/15/2025, 159 shares of common stock were acquired upon RSU vesting, and 47 shares were disposed at $6.71 to cover taxes. After these transactions, the officer directly owns 3,658 shares, with 795 RSUs remaining. The reported amounts reflect the issuer’s 1-for-10 reverse stock split effective 07/21/2025.

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^*

Paone Antoinette

(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)

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

3. Date of Earliest Transaction (Month/Day/Year)
10/15/2025

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	10/15/2025		M		159(1)	A	(2)	3,705(1)	D
Common Stock	10/15/2025		F		47(1)	D	$6.71	3,658(1)	D

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	(2)	10/15/2025		M			159(1)	(3)	(3)	Common Stock	159(1)	$0	795(1)	D

Explanation of Responses:

1. Amounts reported in this Form 4 reflect the one-for-10 reverse stock split effected by the issuer on July 21, 2025.

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

3. On January 20, 2023, the reporting person was granted 2,546 restricted stock units. The shares underlying the restricted stock units vest over four years, with 25% of the shares vested on January 15, 2024 and the remaining shares vesting in equal quarterly installments thereafter.

	/s/ Shawna-Gay White, Attorney-in-Fact	10/17/2025
	** 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 activity did GBIO report on Form 4?

The COO acquired 159 shares from RSU vesting and disposed of 47 shares at $6.71 for taxes on 10/15/2025.

How many GBIO shares does the COO hold after the transactions?

The COO directly owns 3,658 shares following the reported transactions.

How many RSUs remain for the GBIO COO?

The filing shows 795 restricted stock units remain beneficially owned following the transaction.

What price was used for tax withholding on GBIO shares?

$6.71 per share was used for the 47-share tax withholding transaction.

Did a reverse stock split affect the reported amounts for GBIO?

Yes. All amounts reflect the issuer’s 1-for-10 reverse stock split effective 07/21/2025.

What is the reporting person’s role at GBIO?

The reporting person is the Chief Operating Officer.

When were the original RSUs granted and how do they vest?

2,546 RSUs were granted on 01/20/2023, with 25% vesting on 01/15/2024 and the remainder in equal quarterly installments thereafter.