An experimental Metsera obesity drug led to an average 8.4% weight loss in a small clinical trial, preliminary results that keep the biotech competitive in the crowded mix of companies pursuing a promising new metabolic target, but with the potential to offer less frequent dosing than its rivals.
The drug, MET-233i, is a peptide engineered to stand in for amylin, a hormone that, like GLP-1, plays a role in regulating blood sugar and appetite. New York-based Metsera designed MET-233i with technology enabling the medication to last longer in the body.
The 8.4% weight loss mark reported Monday was achieved by the 1.2 mg dose, the highest of four doses of the drug administered weekly for five weeks in a two-part Phase 1 study. Each part enrolled 40 participants. In the single-ascending dose portion of the study, in which a group of participants received just a single dose, the 1.2 mg dose led to an average 3.8% loss in body weight that was maintained for five weeks.
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Metsera said its drug’s half-life of 19 days supports once-monthly dosing. That would be an advantage over the once-weekly dosing of the GLP-1 drugs currently available and the clinical-stage amylin drugs in development by other companies, such as Novo Nordisk, Roche, and AbbVie.
Gastrointestinal side effects, such as nausea and diarrhea, are common for metabolic medicines that target gut receptors to treat obesity. Metsera said these adverse effects in its drug’s Phase 1 study were classified as mild and dose-dependent. The company added that these effects were limited to the first week of dosing, which suggests rapid onset of tolerance.
Metsera expects patients will start at lower doses of the drug to build up to the full dose; at these lower doses, the Phase 1 results show MET-233i’s side effects were comparable to placebo. This dose titration approach is part of the ongoing Phase 1 monotherapy study, which is evaluating 12 weekly doses of MET-233i followed by an exposure-matched monthly dose at week 13. Preliminary data from this study are expected in late 2025
“We observed five-week body weight loss comparable to that of leading GLP-1-based medicines, and we identified efficacious starting doses with placebo-like tolerability,” Metsera Chief Medical Officer Steve Marso said in a prepared statement. “These data position MET-233i as a potential best-in-class amylin and support a category-leading profile in combination with MET-097i.”
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The ability of Metsera’s drugs to achieve longer dosing comes from a platform technology called Half-Life Optimization by Lipid Optimization, or HALO. The technology enables a peptide to bind simultaneously to its target and to albumin, a protein found in the blood. Doing so gives the drug a half-life approaching that of albumin. This protein produced in the liver has a half-life of about three weeks; binding to it has been studied as a way to improve the durability of shorter-lived biologic drugs.
Metsera has also applied HALO to the GLP-1 drug candidate in its pipeline, MET-097i, which is currently in Phase 2b testing as a monotherapy. A 12-week Phase 1 study evaluating the combination of this drug with Metsera’s amylin drug candidate is underway; preliminary data are expected by the end of this year or in early 2026.
Yet another long-acting Metsera drug, MET-034i, is being developed to address the GIP receptor to spark metabolic effects. The company is preparing to advance this drug to the clinic in combination with its GLP-1 drug candidate. Combining GLP-1 and GIP could put Metsera directly in competition with blockbuster Eli Lilly drug Zepbound, but with a potential advantage of once-monthly dosing versus the weekly injections of the Lilly drug. Metsera expects to report preliminary data of its GLP-1 and GIP receptor-targeting drug combination in late 2025.
Metsera was founded in 2022 by Population Health Partners and Arch Venture Partners. In February, the clinical-stage company raised $275 million in one of this year’s few biotech IPOs, which it priced at $18 per share. On Monday, Metsera’s opening stock price was $31.60, up nearly 15% from Friday’s closing price.
Photo: Peter Dazeley, Getty Images