Also known as SRK-015 · SRK-439
A monoclonal antibody that selectively blocks pro/latent myostatin — the muscle brake — studied to preserve lean mass during GLP-1 weight loss.
Research refreshed
Apitegromab is a fully human monoclonal antibody (Scholar Rock) and the first of the anti-myostatin biologics in this catalog. Where myostatin is the growth factor that brakes muscle and follistatin is the body’s natural antagonist, apitegromab is an engineered antagonist: an antibody that binds the inactive precursor forms of myostatin (pro- and latent myostatin) and prevents their activation. Its selectivity for those precursors — rather than mature myostatin or the related GDF11/activins — is its defining design feature.
Apitegromab’s lead program is in spinal muscular atrophy (SMA), where it is added on top of SMN-targeted therapy to build motor-relevant muscle. That application is close to a regulatory answer: after a September 2025 Complete Response Letter tied to a routine inspection at a third-party (Novo Nordisk) manufacturing facility — not to the drug’s efficacy or safety — Scholar Rock resubmitted the application, and the FDA set a decision date of September 30, 2026.
The same mechanism drives its forward-looking metabolic use. In the Phase 2 EMBRAZE trial (published in Nature Medicine, 2026), tirzepatide alone lost about 30% of its weight as lean mass; adding apitegromab preserved an additional 1.9 kg (~4.2 lb), or 54.9% of the lean mass that would otherwise have been lost, and was generally well tolerated — its precursor-selectivity framed as a potential tolerability advantage over broader myostatin/activin blockers. As a biologic it sits a full step beyond the protein hormones elsewhere in this catalog: an antibody (~150 kDa), produced in mammalian cells, designed to deplete a specific target. It is included here as the antibody arm of the myostatin axis that myostatin and follistatin introduce.
Binds pro-myostatin and latent myostatin, blocking the proteolytic activation that releases mature, active myostatin. Lowering active myostatin disinhibits muscle growth via the ActRIIB/Smad pathway.
Behind every vial of Apitegromab is the same exacting pipeline every research peptide runs — but the chemistry plays out differently for this molecule. Here is how Apitegromab, specifically, is brought into being.
On paper, Apitegromab weighs in at roughly 150,000 daltons. Before a single bond is made, the target sequence, salt form, and purity threshold are written down as the contract the finished material must meet.
Apitegromab is assembled by solid-phase peptide synthesis — the chain grows one protected residue at a time on resin, and what you fail to build cleanly here you pay to remove later.
The crude mixture — Apitegromab plus its deletions and side products — is then separated on preparative HPLC, and where the cut is taken decides the difference between a genuinely pure peptide and a barely-passable one.
A real batch of Apitegromab proves itself: identity confirmed by mass spectrometry against its ~150,000 Da, purity read directly off an analytical HPLC trace, water and counterion content measured. That batch-specific certificate of analysis is the only honest way to know what is actually in a vial of Apitegromab — and a short, cold, accountable chain of custody is how that purity survives the trip to your bench.
Apitegromab is a recombinant monoclonal antibody (~150 kDa) produced in mammalian cell culture — the most complex biologic class in this catalog, far removed from solid-phase peptide synthesis. Characterization is antibody-grade: glycan and charge-variant profiling, identity by mass spectrometry, and target-binding/cell-based potency, with host-cell-protein and endotoxin limits.
Don't judge a vial by its cake. A fluffy, good-looking lyophilized powder reflects bulking agents and freeze-drying parameters — not purity. Insist on a batch-specific certificate of analysis.
Recent clinical trials and publications mentioning Apitegromab, pulled automatically from ClinicalTrials.gov and PubMed and refreshed daily. Listings are unfiltered search results, not curated endorsements.
A monoclonal antibody that selectively blocks the precursor forms of myostatin, the growth factor that limits muscle. It is studied in spinal muscular atrophy and, in combination with GLP-1/GIP drugs, to preserve muscle during weight loss.
Apitegromab targets pro- and latent (inactive) myostatin before it is activated, rather than the mature protein — a selectivity intended to avoid hitting related factors and improve tolerability.
In the Phase 2 EMBRAZE trial (Nature Medicine, 2026), participants on tirzepatide alone lost about 30% of their weight as lean mass. Adding apitegromab preserved an additional 1.9 kg (~4.2 lb) — 54.9% of the lean mass that would otherwise have been lost — and was generally well tolerated.
No — this is a research and educational reference. Apitegromab is an investigational antibody; its SMA application is under FDA review (decision date Sept 30, 2026) and it is not approved for any use.
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ViewDosing protocols, mechanism, comparisons, and the latest trials — citation-backed answers grounded in PubMed, PubChem, and ClinicalTrials.gov.