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MBX SCHEDULE 13D/A: SEC filing

Frazier Life Sciences entities and associated individuals

Filed with the SEC on · accession 0001231919-26-000851

MBX filed a SCHEDULE 13D/A (schedule 13d/a) with the SEC on Aug 10, 2026. Frazier Life Sciences entities and associated individuals filed a joint filing agreement under Schedule 13D/A regarding their ownership of MBX Biosciences common stock. The stock moved -2.5% by the first close after the filing.

Summary of the filing

Frazier Life Sciences entities and associated individuals filed a joint filing agreement under Schedule 13D/A regarding their ownership of MBX Biosciences common stock. The filing is a procedural exhibit and does not disclose any change in ownership or intent.

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Key details

Subject companyMBX Biosciences, Inc.
FilerFrazier Life Sciences Public Fund, L.P.
General partner of filerFHMLSP, L.P.
General partner of fhmlsp, l.p.FHMLSP, L.L.C.
FilerFrazier Life Sciences X, L.P.
General partner of filerFHMLS X, L.P.
General partner of fhmls x, l.p.FHMLS X, L.L.C.
FilerFrazier Life Sciences XI, L.P.
General partner of filerFHMLS XI, L.P.
General partner of fhmls xi, l.p.FHMLS XI, L.L.C.
Chief financial officer, fhmlsp, l.l.c.Jennifer Martin
Individual filerJames N. Topper
Individual filerPatrick J. Heron

How MBX stock reacted

Close before

$67.82

Aug 7, 2026

First close after

-2.46%

$66.15

5 trading days

+1.11%

$68.57

Since filing

-24.28%

$51.35

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Frequently asked questions

What did MBX file with the SEC on Aug 10, 2026?

MBX filed a SCHEDULE 13D/A (SEC filing). Frazier Life Sciences entities and associated individuals filed a joint filing agreement under Schedule 13D/A regarding their ownership of MBX Biosciences common stock. The filing is a procedural exhibit and does not disclose any change in ownership or intent.

How do I read a SCHEDULE 13D/A?

A report the company filed with the SEC (the US market regulator). Start with the summary, then the key amounts and names. Compare it with the company’s earlier filings.

Why are SEC filings important?

Public companies must tell the SEC about anything that can change their value — results, leadership changes, big deals, new shares, bankruptcy. Filings are the official source, often before the news. A SCHEDULE 13D/A (schedule 13d/a): A report the company filed with the SEC (the US market regulator).

How did MBX stock react to this filing?

MBX closed at $67.82 before the filing and $66.15 on Aug 10, 2026 (-2.46%). Five trading days later: $68.57 (+1.11%).

Other MBX SEC filings

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