Welcome to our dedicated page for MBX Biosciences SEC filings (Ticker: MBX), a comprehensive resource for investors and traders seeking official regulatory documents including 10-K annual reports, 10-Q quarterly earnings, 8-K material events, and insider trading forms.
Parsing a biotech filing can feel like decoding a medical journal—especially when MBX Biosciences packs its 10-K with pages of pharmacokinetic data on its PEP platform and tables of Phase 1 safety results. If you are searching “MBX SEC filings explained simply” or wondering how the company’s R&D spend aligns with upcoming trial milestones, you are not alone. Investors need quick clarity on how precision peptide programs translate into shareholder value.
Stock Titan delivers that clarity by pairing every MBX document—whether a quarterly earnings report 10-Q filing or an 8-K material event—with AI-powered summaries that turn dense scientific and accounting language into plain English. Our engine flags key passages on cash runway, licensing deals, and clinical-trial endpoints, while real-time alerts surface MBX Form 4 insider transactions the moment executives buy or sell shares. You will also find side-by-side views of historical 10-K risk factors, MBX proxy statement executive compensation details, and S-1/A capital-raising terms, all linked to easy-to-read AI notes.
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Amendment No. 1 to the Schedule 13D reports that Norwest Venture Partners XVI, LP and affiliated reporting persons experienced dilution in their ownership of MBX Biosciences, Inc. common stock as a result of an underwritten public offering that closed on September 26, 2025. The filing states each of the primary reporting persons beneficially owns 2,136,335 shares, representing 4.8% of the class based on 33,607,443 shares outstanding as of August 31, 2025 plus 11,108,055 shares issued in the offering; Ms. Aynechi’s aggregate beneficial ownership is reported as 2,140,989 shares (including 4,654 option shares). The reporting group ceased to be beneficial owners of more than 5% on September 26, 2025. The amendment discloses no transactions in the past 60 days and incorporates a prior joint filing agreement as an exhibit.
Frazier-affiliated investment vehicles disclosed their holdings in MBX Biosciences, Inc. Frazier Life Sciences X, L.P. directly holds 5,219,440 shares of common stock, representing 11.7% of the class based on the filing's share-count assumptions. Frazier Life Sciences Public Fund, L.P. holds 1,103,920 shares (2.5%), and Frazier Life Sciences Public Overage Fund, L.P. holds 325,653 shares (0.7%). The filing details pre-IPO purchases of preferred stock that converted at a 12.0221-to-1 ratio at IPO, IPO purchases at $16.00 per share, and a post-IPO purchase on September 26, 2025 by FLS X of 666,666 shares at $18.00 per share. The filing clarifies voting and dispositive power allocations among related entities and identifies exhibits, including an investors' rights agreement and a transactions exhibit.
MBX Biosciences Form 4 summary: On 09/26/2025 an affiliated investor group acquired 666,666 shares of MBX common stock at $18.00 per share. After the reported purchase the group beneficially owned 5,219,440 shares. The shares are held of record by Frazier Life Sciences X, L.P., with FHMLS X, L.P., FHMLS X, L.L.C., James N. Topper and Patrick J. Heron having shared voting and investment power; Heron is identified as a reporting person and a director and 10% owner. The filing is signed by an attorney-in-fact on behalf of the reporting parties.
MBX Biosciences describes a pipeline built on a proprietary PEP platform targeting endocrine and metabolic diseases. Lead candidate canvuparatide (MBX 2109) is a PTH peptide prodrug designed for once-weekly dosing; Phase 1 showed a low peak-to-trough ratio, extended half-life, and no drug-related severe or serious adverse effects. A Phase 2 trial enrolled 64 hypoparathyroidism patients, enrollment completed March 2025, and topline data were reported September 2025. At 12 weeks, the primary composite endpoint was achieved in 63% (30/48) of treated patients vs 31% (5/16) placebo (p=0.042); 6-month OLE responder rate was 79% (44/56). Pharmacokinetics supported once-weekly dosing; bone turnover markers increased and urine calcium fell in responders. Safety: mostly mild/moderate adverse events, injection site reactions 19% vs 13% placebo, no deaths or drug-related serious adverse events.
Other programs include imapextide (MBX 1416) (long-acting GLP-1 receptor antagonist) with Phase 1 median half-life ~90 hours, favorable safety, End-of-Phase 1 FDA meeting completed and Phase 2a anticipated Q3 2025; and obesity candidate MBX 4291 (GLP-1/GIP co-agonist prodrug) with IND submitted June 16, 2025, FDA clearance July 2025, Phase 1 initiated September 2025 and topline results expected in 2027. The offering price referenced is $18.00 per share and the company expects proceeds to fund development, including approximately $248.0 million to advance the three clinical-stage programs.
MBX Biosciences is advancing a pipeline of long‑acting peptide prodrugs built on its proprietary PEP platform, focused on hypoparathyroidism (HP), post‑bariatric hypoglycemia (PBH) and obesity. Its lead candidate, canvuparatide (MBX 2109), is intended as a once‑weekly PTH replacement; a Phase 2 trial enrolled 64 patients, completed enrollment in March 2025 and reported topline data in September 2025. At 12 weeks the primary composite endpoint was met in 63% of treated patients versus 31% for placebo (p=0.042). In an open‑label extension, 79% of evaluable patients were responders at six months. Pharmacokinetics support once‑weekly dosing and canvuparatide was generally well tolerated with no drug‑related serious adverse events. Imapextide (MBX 1416) showed a median half‑life of 90 hours in Phase 1, is expected to begin Phase 2a in Q3 2025 after an End‑of‑Phase 1 FDA meeting. MBX 4291 (obesity) received IND clearance in July 2025 and initiated Phase 1 in September 2025 with topline results anticipated in 2027. The prospectus discloses financing assumptions (an illustrative 10,000,000 share offering at $10.00) and an estimated need of approximately $248.0 million to advance the three clinical programs through stated milestones.
Frazier Life Sciences-related funds report holdings in MBX Biosciences following IPO conversions and purchases. Frazier Life Sciences X, L.P. holds 4,552,774 shares (13.6% of 33,593,866 outstanding), Frazier Life Sciences Public Fund, L.P. holds 1,103,920 shares (3.3%), Frazier Life Sciences Public Overage Fund, L.P. holds 325,653 shares (1.0%), and FLS XI holds 3,000 shares. These positions arose from pre-IPO preferred-stock purchases that converted at a 12.0221-to-1 ratio plus additional IPO purchases at $16.00 per share. The filers state purchases were funded from each fund's working capital and correct prior attributions of beneficial ownership for certain investment committee members.
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