Phillip Samayoa - 15 Oct 2025 Form 4 Insider Report for Generation Bio Co. (GBIO)

Reporting relationship: CHIEF SCIENTIFIC OFFICER
Issuer ticker: GBIO
Reported as of: 15 Oct 2025
Net transaction value: -$228
SEC form: 4
Accepted by SEC: 17 Oct 2025, 16:05:16 UTC
Prior SEC filing: 17 Jul 2025
Next SEC filing: 31 Oct 2025
Source filing: View source filing
Reporting owner signature: /s/ Shawna-Gay White, Attorney-in-Fact

Key filing fact

Phillip Samayoa filed Form 4 for Generation Bio Co. (GBIO) on 17 Oct 2025.

Key facts

This page summarizes Phillip Samayoa's Form 4 filing for Generation Bio Co. (GBIO).
3 reported transactions and 1 derivative row are listed below.
Accepted by SEC: 17 Oct 2025, 16:05.

Change

Previous filing in this sequence was filed on 17 Jul 2025.
Current net transaction value: -$228.

Research use

This tells you what this filing adds before you inspect full transaction and derivative tables.
You can trace every row back to the original SEC filing document.

Evidence

Filed on Form 4

Ownership activity is grounded in SEC Form 4 disclosures.

View source filing

Reporting Owners (1)

CIK 0001946316 Primary reporting owner

Samayoa Phillip

Relationship: CHIEF SCIENTIFIC OFFICER
Address: C/O GENERATION BIO CO., 301 BINNEY STREET, SUITE 401, CAMBRIDGE
Signature: /s/ Shawna-Gay White, Attorney-in-Fact
Signature date: 17 Oct 2025

Reported non-derivative transactions

Shares, units, or other non-derivative securities reported in this filing.

GBIO transaction

Common Stock

Options Exercise

Transaction value
Shares: +114
Change %: +0.81%
Price
Shares after: 14,172
Date: 15 Oct 2025
Ownership: Direct
Footnotes: F1, F2

GBIO transaction

Common Stock

Tax liability

Transaction value: $228
Shares: -34
Change %: -0.24%
Price: $6.71
Shares after: 14,138
Date: 15 Oct 2025
Ownership: Direct
Footnotes: F1

Reported derivative securities

Options, warrants, convertible securities, or similar derivative positions disclosed in the filing.

GBIO transaction Derivative

Restricted Stock Units

Options Exercise

Transaction value: $0
Shares: -114
Change %: -17%
Price: $0.000000
Shares after: 573
Date: 15 Oct 2025
Ownership: Direct
Underlying class: Common Stock
Underlying amount: 114
Exercise price
Footnotes: F1, F2, F3

^* marks a reported price that did not pass the local price check.

Additional SEC filing notes

Filing notes and footnotes

Explanation of responses 3 footnotes

Footnote F1

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

Footnote F2

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

Footnote F3

On January 20, 2023, the reporting person was granted 1,834 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.