Flagship Ventures Fund V, L.P. - 09 Jan 2026 SCHEDULE 13D/A Report for FOGHORN THERAPEUTICS INC. Common Stock, $0.0001 par value per share (FHTX)

Filing manager
Flagship Ventures Fund V, L.P.
Reporting owner
Noubar Afeyan
Security
FOGHORN THERAPEUTICS INC. Common Stock, $0.0001 par value per share
Beneficially owned shares
20,774,885 shares
Ownership signal CIK-linked ownership evidence from parsed SEC filings. 2 signals
Large-stake signal

Form

SCHEDULE 13D/A

Active or control-oriented beneficial ownership filing.

Ownership

27%

Beneficial ownership of this reported class.

Shares

20,774,885 shares

Shares beneficially owned as disclosed.

Event date

09 Jan 2026

Date tied to the ownership event or amendment.

Accepted by SEC

13 Jan 2026

EDGAR acceptance date.

How to read this large-stake filing
  • Schedule 13D/G filings focus on beneficial ownership stakes, not a full portfolio.
  • Compare this filing with the holder history and issuer page before treating the percentage as a current position.
  • Use amendments to understand whether the disclosed stake increased, decreased, or changed reporting status.
Class ownership
27%
Subject security Names, identifiers, and filing context for this profile. 2 source fields
Symbol
FHTX
Shares outstanding
76,378,254 shares
Source evidence Original filing metadata and source links for verification. 4 source fields
SEC form
SCHEDULE 13D/A
Accepted by SEC
13 Jan 2026, 17:09:10 UTC
Event date
09 Jan 2026
Source filing
View source filing

Key filing fact

Flagship Ventures Fund V, L.P. disclosed 27% ownership in FOGHORN THERAPEUTICS INC. Common Stock, $0.0001 par value per share (FHTX) on 09 Jan 2026.

Key facts

  • Flagship Ventures Fund V, L.P. filed SCHEDULE 13D/A for FOGHORN THERAPEUTICS INC. Common Stock, $0.0001 par value per share (FHTX).
  • Disclosed ownership: 27%.
  • Date of event: 09 Jan 2026.

Change

  • No earlier schedule filing is available for direct comparison.
  • Current filing was accepted on 13 Jan 2026, 17:09.

Research use

  • This page turns one Schedule 13D/G filing into a quick large-stake read before the raw reporting-person rows.
  • Use the linked SEC filing as the source of truth for ownership percentages, shares, and reporting-party details.

Evidence

Backed by Schedule 13D/13G

Beneficial ownership values are sourced from the original SEC Schedule 13D/13G filing.

View source filing

Reporting persons

Disclosed reporting parties (10)

Names, ownership percentages, voting power, signatures, titles, and CIKs as disclosed in this Schedule 13D/G filing.

Name Ownership Shares owned Sole voting power Shared voting power Signature Title CIK
Flagship Ventures Fund V, L.P. 16% 9,330,878 0 9,330,878 /s/ Noubar B. Afeyan, Ph.D. Noubar B. Afeyan, Ph.D., Manager of General Partner 0001627639
Flagship Ventures Fund V General Partner LLC 16% 9,330,878 0 9,330,878 /s/ Noubar B. Afeyan, Ph.D. Noubar B. Afeyan, Ph.D., Manager
Flagship Ventures Opportunities Fund I, L.P. 2.5% 1,491,441 0 1,491,441 /s/ Noubar B. Afeyan, Ph.D. Noubar B. Afeyan, Ph.D., Manager of General Partner
Flagship Ventures Opportunities Fund I General Partner LLC 2.5% 1,491,441 0 1,491,441 /s/ Noubar B. Afeyan, Ph.D. Noubar B. Afeyan, Ph.D., Manager
Flagship Pioneering Special Opportunities Fund II, L.P. 3.2% 3,666,715 0 3,666,715 /s/ Noubar B. Afeyan, Ph.D. Noubar B. Afeyan, Ph.D., Sole Member and Manager of Manager of Manager of General Partner
Flagship Pioneering Special Opportunities Fund II General Partner LLC 3.2% 3,666,715 0 3,666,715 /s/ Noubar B. Afeyan, Ph.D. Noubar B. Afeyan, Ph.D., Sole Member and Manager of Manager of Manager
Flagship Pioneering Fund VII, L.P. 7.1% 6,285,851 0 6,285,851 /s/ Noubar B. Afeyan, Ph.D. Noubar B. Afeyan, Ph.D., Sole Member and Manager of Manager of Manager of General Partner
Flagship Pioneering Fund VII General Partner LLC 7.1% 6,285,851 0 6,285,851 /s/ Noubar B. Afeyan, Ph.D. Noubar B. Afeyan, Ph.D., Sole Member and Manager of Manager of Manager
Flagship Pioneering, LLC 10% 9,952,566 0 9,952,566 /s/ Noubar B. Afeyan, Ph.D. Noubar B. Afeyan, Ph.D., Sole Member and Manager of Manager
Noubar Afeyan 27% 20,774,885 0 20,774,885 /s/ Noubar B. Afeyan, Ph.D. Noubar B. Afeyan, Ph.D.
We use cookies and similar technologies to provide certain features, enhance the user experience and, if you allow them, measure engagement and deliver advertising. Analytics and marketing storage stay off until you grant consent. By clicking on "Agree and continue", you declare your consent to the use of the selected optional cookies. Manage preferences to update or revoke optional consent for future visits. For more information, see our Privacy Policy .