Form
SCHEDULE 13D/A
Active or control-oriented beneficial ownership filing.
Frazier Life Sciences Public Fund, L.P. - 06 Aug 2026 SCHEDULE 13D/A Report for MBX BIOSCIENCES, INC. Common Stock, $0.0001 par value per share (MBX)
- Filing manager
- Frazier Life Sciences Public Fund, L.P.
- Reporting owner
- Patrick J. Heron
- Beneficially owned shares
- 5,243,421 shares
- Large-stake signal
-
Ownership
12%Beneficial ownership of this reported class.
Shares
5,243,421 sharesShares beneficially owned as disclosed.
Event date
06 Aug 2026Date tied to the ownership event or amendment.
Accepted by SEC
10 Aug 2026EDGAR 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
- 12%
- Symbol
- MBX
- Shares outstanding
- 44,815,564 shares
- SEC form
- SCHEDULE 13D/A
- Accepted by SEC
- 10 Aug 2026, 17:35:46 UTC
- Event date
- 06 Aug 2026
- Prior SEC filing
- 30 Sep 2025
- Source filing
- View source filing
Ownership signal
CIK-linked ownership evidence from parsed SEC filings.
2 signals
Subject security
Names, identifiers, and filing context for this profile.
2 source fields
Source evidence
Original filing metadata and source links for verification.
5 source fields
Key filing fact
Frazier Life Sciences Public Fund, L.P. disclosed 12% ownership in MBX BIOSCIENCES, INC. Common Stock, $0.0001 par value per share (MBX) on 06 Aug 2026.
Key facts
- Frazier Life Sciences Public Fund, L.P. filed SCHEDULE 13D/A for MBX BIOSCIENCES, INC. Common Stock, $0.0001 par value per share (MBX).
- Disclosed ownership: 12%.
- Date of event: 06 Aug 2026.
Change
- Previous schedule filing date: 30 Sep 2025.
- Current filing was accepted on 10 Aug 2026, 17:35.
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
View source filing
Beneficial ownership values are sourced from the original SEC Schedule 13D/13G filing.
Reporting persons
Disclosed reporting parties (11)
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 |
|---|---|---|---|---|---|---|---|
| Frazier Life Sciences Public Fund, L.P. | 3% | 1,429,573 | 0 | 1,429,573 | /s/ Jennifer Martin | By Jennifer Martin, CFO of FHMLSP, L.L.C., GP of FHMLSP, L.P., GP of Frazier Life Sciences Public Fund, L.P. | 0001863769 |
| FHMLSP, L.P. | 3% | 1,429,573 | 0 | 1,429,573 | /s/ Jennifer Martin | By Jennifer Martin, CFO of FHMLSP, L.L.C., GP of FHMLSP, L.P. | 0001879466 |
| FHMLSP, L.L.C. | 3% | 1,429,573 | 0 | 1,429,573 | /s/ Jennifer Martin | By Jennifer Martin, CFO of FHMLSP, L.L.C. | 0001879465 |
| Frazier Life Sciences X, L.P. | 11% | 5,219,440 | 0 | 5,219,440 | /s/ Jennifer Martin | By Jennifer Martin, CFO of FHMLS X, L.L.C., GP of FHMLS X, L.P., GP of Frazier Life Sciences X, L.P. | 0001790879 |
| FHMLS X, L.P. | 11% | 5,219,440 | 0 | 5,219,440 | /s/ Jennifer Martin | By Jennifer Martin, CFO of FHMLS X, L.L.C., GP of FHMLS X, L.P. | 0001790880 |
| FHMLS X, L.L.C. | 11% | 5,219,440 | 0 | 5,219,440 | /s/ Jennifer Martin | By Jennifer Martin, CFO of FHMLS X, L.L.C. | 0001790811 |
| Frazier Life Sciences XI, L.P. | 0% | 3,000 | 0 | 3,000 | /s/ Jennifer Martin | By Jennifer Martin, CFO of FHMLS XI, L.L.C., GP of FHMLS XI, L.P., GP of Frazier Life Sciences XI, L.P. | 0001911592 |
| FHMLS XI, L.P. | 0% | 3,000 | 0 | 3,000 | /s/ Jennifer Martin | By Jennifer Martin, CFO of FHMLS XI, L.L.C., GP of FHMLS XI, L.P. | 0001911580 |
| FHMLS XI, L.L.C. | 0% | 3,000 | 0 | 3,000 | /s/ Jennifer Martin | By Jennifer Martin, CFO of FHMLS XI, L.L.C. | 0001911623 |
| James N. Topper | 12% | 5,219,440 | 0 | 5,219,440 | /s/ Jennifer Martin | By Jennifer Martin, Attorney-in-Fact for James N. Topper, pursuant to Power of Attorney | 0001341382 |
| Patrick J. Heron | 12% | 5,243,421 | 23,981 | 5,219,440 | /s/ Jennifer Martin | By Jennifer Martin, Attorney-in-Fact for Patrick J. Heron, pursuant to Power of Attorney | 0001365617 |
CIK / CUSIP context first