Flagship Pioneering, LLC - 13 Jan 2026 Form 4 Insider Report for Foghorn Therapeutics Inc. (FHTX)

Reporting relationship: Director, 10%+ Owner
Issuer ticker: FHTX
Reported as of: 13 Jan 2026
Net transaction value: +$14,999,767
SEC form: 4
Accepted by SEC: 15 Jan 2026, 17:00:05 UTC
Prior SEC filing: 24 May 2024
Source filing: View source filing
Reporting owner signature: Flagship Pioneering, LLC, By: /s/ Noubar B. Afeyan, Ph.D., Title: Sole Member and Manager of Manager

Key filing fact

Flagship Pioneering, LLC filed Form 4 for Foghorn Therapeutics Inc. (FHTX) on 15 Jan 2026.

Key facts

This page summarizes Flagship Pioneering, LLC's Form 4 filing for Foghorn Therapeutics Inc. (FHTX).
3 reported transactions and 3 derivative rows are listed below.
Accepted by SEC: 15 Jan 2026, 17:00.

Change

Previous filing in this sequence was filed on 24 May 2024.
Current net transaction value: +$14,999,767.

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 (10)

CIK 0001400240 Primary reporting owner

Flagship Pioneering, LLC

Relationship: Director, 10%+ Owner
Address: 55 CAMBRIDGE PARKWAY, SUITE 800E, CAMBRIDGE
Signature: Flagship Pioneering, LLC, By: /s/ Noubar B. Afeyan, Ph.D., Title: Sole Member and Manager of Manager
Signature date: 15 Jan 2026

CIK 0001805917

Flagship Pioneering Fund VII General Partner LLC

Relationship: Director, 10%+ Owner
Address: 55 CAMBRIDGE PARKWAY, SUITE 800E, CAMBRIDGE
Signature: Flagship Pioneering Fund VII General Partner LLC, By: /s/ Noubar B. Afeyan, Ph.D., Title: Sole Member and Manager of Manager of Manager
Signature date: 15 Jan 2026

CIK 0001805916

Flagship Pioneering Fund VII, L.P.

Relationship: Director, 10%+ Owner
Address: 55 CAMBRIDGE PARKWAY, SUITE 800E, CAMBRIDGE
Signature: Flagship Pioneering Fund VII, L.P., By: /s/ Noubar B. Afeyan, Ph.D., Title: Sole Member and Manager of Manager of Manager of General Partner
Signature date: 15 Jan 2026

CIK 0001826217

Flagship Pioneering Special Opportunities Fund II General Partner LLC

Relationship: Director, 10%+ Owner
Address: 55 CAMBRIDGE PARKWAY, SUITE 800E, CAMBRIDGE
Signature: Flagship Pioneering Special Opportunities Fund II General Partner LLC, By: /s/ Noubar B. Afeyan Ph.D., Title: Sole Member and Manager of Manager
Signature date: 15 Jan 2026

CIK 0001761283

Flagship Pioneering Special Opportunities Fund II, L.P.

Relationship: Director, 10%+ Owner
Address: 55 CAMBRIDGE PARKWAY, SUITE 800E, CAMBRIDGE
Signature: Flagship Pioneering Special Opportunities Fund II, L.P., By: /s/ Noubar B. Afeyan Ph.D., Title: Sole Member and Manager of Manager of Manager of General Partner
Signature date: 15 Jan 2026

CIK 0001724575

Flagship Ventures Fund V General Partner LLC

Relationship: Director, 10%+ Owner
Address: 55 CAMBRIDGE PARKWAY, SUITE 800E, CAMBRIDGE
Signature: Flagship Ventures Fund V General Partner LLC, By: /s/ Noubar B. Afeyan Ph.D., Title: Manager
Signature date: 15 Jan 2026

CIK 0001627639

Flagship Ventures Fund V, L.P.

Relationship: Director, 10%+ Owner
Address: 55 CAMBRIDGE PARKWAY, SUITE 800E, CAMBRIDGE
Signature: Flagship Ventures Fund V, L.P., By: /s/ Noubar B. Afeyan Ph.D., Title: Manager of General Partner
Signature date: 15 Jan 2026

CIK 0001725004

Flagship Ventures Opportunities Fund I General Partner LLC

Relationship: Director, 10%+ Owner
Address: 55 CAMBRIDGE PARKWAY, SUITE 800E, CAMBRIDGE
Signature: Flagship Ventures Opportunities Fund I General Partner LLC, By: /s/ Noubar B. Afeyan Ph.D., Title: Manager
Signature date: 15 Jan 2026

CIK 0001677345

Flagship Ventures Opportunities Fund I, L.P.

Relationship: Director, 10%+ Owner
Address: 55 CAMBRIDGE PARKWAY, SUITE 800E, CAMBRIDGE
Signature: Flagship Ventures Opportunities Fund I, L.P., By: /s/ Noubar B. Afeyan Ph.D., Title: Manager of General Partner
Signature date: 15 Jan 2026

CIK 0001222012

AFEYAN NOUBAR

Relationship: Director, 10%+ Owner
Address: 55 CAMBRIDGE PARKWAY, SUITE 800E, CAMBRIDGE
Signature: /s/ Noubar B. Afeyan, Ph.D.
Signature date: 15 Jan 2026

Reported derivative securities

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

FHTX transaction Derivative

Pre-Funded Warrants to purchase Common Stock

Award

Transaction value: $14,999,767
Shares: +2,235,468
Change %
Price: $6.71
Shares after: 2,235,468
Date: 13 Jan 2026
Ownership: By Flagship Pioneering Fund VII, L.P.
Underlying class: Common Stock
Underlying amount: 2,235,468
Exercise price: $0.000100
Footnotes: F1, F2

FHTX transaction Derivative

Series 1 Warrants to purchase Common Stock

Award

Transaction value
Shares: +1,117,734
Change %
Price
Shares after: 1,117,734
Date: 13 Jan 2026
Ownership: By Flagship Pioneering Fund VII, L.P.
Underlying class: Common Stock
Underlying amount: 1,117,734
Exercise price: $13.42
Footnotes: F1, F2, F3

FHTX transaction Derivative

Series 2 Warrants to purchase Common Stock

Award

Transaction value
Shares: +1,117,734
Change %
Price
Shares after: 1,117,734
Date: 13 Jan 2026
Ownership: By Flagship Pioneering Fund VII, L.P.
Underlying class: Common Stock
Underlying amount: 1,117,734
Exercise price: $20.13
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

On January 13, 2026, pursuant to a registered direct offering by the Issuer, Flagship Pioneering Fund VII, L.P. ("Flagship Fund VII") acquired warrants to purchase an aggregate of 4,470,936 shares of Common Stock, consisting of (i) Pre-Funded Warrants to purchase 2,235,468 shares of Common Stock, (ii) Series 1 Warrants to purchase 1,117,734 shares of Common Stock and (iii) Series 2 Warrants to purchase 1,117,734 shares of Common Stock (together with the Series 1 Warrants, the "Series Warrants"). The securities were acquired for a purchase price of $6.7099 per Pre-Funded Warrant and accompanying Series Warrants.

Footnote F2

Securities held by Flagship Fund VII. Flagship Pioneering Fund VII General Partner LLC ("Flagship Fund VII GP") is the general partner of Flagship Fund VII. Flagship Pioneering, LLC (f/k/a Flagship Pioneering, Inc., "Flagship Pioneering") is the manager of Flagship Fund VII GP. Noubar B. Afeyan, Ph.D. is the ultimate control person of Flagship Pioneering. Each of the Reporting Persons disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein, if any.

Footnote F3

The Series Warrants are exercisable at an initial price of $13.42 per Series 1 Warrant and $20.13 per Series 2 Warrant. Subject to certain exclusions, if prior to June 30, 2027, the Company issues capital stock or securities convertible into or exercisable for capital stock in one or more related transactions primarily for capital raising at a weighted-average common stock equivalent price (the "Weighted-Average Price") below $13.42 per share, the exercise price of a Series Warrant shall reset upon exercise to the midpoint between the initial price and the lowest such Weighted-Average Price, but not below $6.71 per share. The exercise price may be adjusted only once pursuant to this mechanism.

SEC remarks

Douglas G. Cole, a Managing Partner at Flagship Pioneering, serves on the board of directors of the Issuer and has been deputized to represent the Reporting Persons on the board of directors of the Issuer. By virtue of Mr. Cole's representation, for purposes of Section 16 of the Securities Exchange Act of 1934 (the "Exchange Act"), each of the Reporting Persons may be deemed directors by deputization of the Issuer. This filing shall not be deemed an admission that any Reporting Person is a beneficial owner of the securities reported in this filing for purposes of Section 16 of the Exchange Act or otherwise, or is subject to Section 16 of the Exchange Act, and each Reporting Person disclaims beneficial ownership of these securities, except to the extent of such Reporting Person's pecuniary interest therein, if any.