Myostatin, also called GDF-8, is a protein the body makes to limit muscle growth, so blocking it is a long-studied route to building or protecting muscle. Drugs aimed at this pathway include Scholar Rock's apitegromab and Biohaven's taldefgrobep alfa, which target myostatin itself, and Lilly's bimagrumab, which blocks the activin type II receptors that myostatin acts through.
Interest grew as GLP-1 drugs spread, because part of the weight they remove is muscle. On October 1, 2026, Regeneron reported 52-week Phase 2 COURAGE results in which its anti-myostatin antibody trevogrumab, added to semaglutide, limited lean mass loss to 4.2% at 75 mg versus 7.3% on semaglutide alone, and an MRI substudy found about 70% of thigh-muscle loss prevented. Roche went the other way on September 28, 2026, dropping its anti-latent myostatin antibody emugrobart for obesity after an interim look at the Phase 2 GYMINDA trial.
See #muscle-wasting, #sarcopenia, and #cachexia.
Chugai announced on Monday, September 28, 2026 that Roche is discontinuing development of emugrobart (GYM329), a subcutaneous anti-latent myostatin antibody, for obesity after an interim analysis of the Phase 2 GYMINDA study concluded that the trial was unlikely to meet its pre-specified weight-loss objectives. GYMINDA tested emugrobart in combination with GLP-1/GIP receptor agonists in people with obesity or overweight; Chugai said the antibody was well tolerated, with no new safety signals. All rights return to Chugai, which is preparing to resume development in spinal muscular atrophy and considering out-licensing; Roche had already stopped emugrobart development in spinal muscular atrophy and facioscapulohumeral muscular dystrophy in March 2026.
Hanmi Pharmaceutical presented HM500197 (LA-MSTN) at ADA 2026 (June 5-8, New Orleans) as the world's first peptide-based myostatin inhibitor, positioned as a muscle-preserving adjunct to GLP-1 weight-loss therapy. The molecule was designed on Hanmi's HARP (Hanmi AI-driven Research Platform) integrating AI and structural modeling. Hanmi paired the LA-MSTN unveiling with a second next-generation candidate, HM17321, in a broader eight-abstract slate spanning the company's obesity pipeline. The myostatin angle addresses a major shortcoming of the current GLP-1 class — 25-40% of weight loss coming from lean tissue rather than fat — which Stanford's Maharjan team flagged at ENDO 2026 with the 560-step daily activity drop and which underlies the broader bone-health and frailty concerns now being studied across the GLP-1 class.
A 2026 scoping review in the Journal of Cachexia, Sarcopenia and Muscle catalogs peptides studied as therapeutic candidates and biomarkers in skeletal muscle wasting — covering sarcopenia, cancer cachexia, and ICU-related atrophy. The review documents MIF1/MIF2 myostatin peptide inhibitors, cachexia-targeting platform peptides, and the broader role of GH-axis peptides (CJC-1295, ipamorelin, tesamorelin) in muscle homeostasis. The clinical urgency lands harder now than it did pre-2024: Nature Reviews Endocrinology recently flagged sarcopenia and frailty as under-recognized GLP-1 receptor agonist side effects, with up to 40% of GLP-1-induced weight loss attributable to lean mass in the highest-loss patients. The review surfaces non-GLP-1 peptide candidates that could be paired with incretin therapy to protect muscle.
Scholar Rock's apitegromab — a selective pro/latent myostatin antibody approved for SMA — continues to draw obesity-pipeline attention with EMBRAZE Phase 2 data showing 54.9% relative lean mass preservation when combined with tirzepatide vs tirzepatide alone (4.2 lbs / 1.9 kg additional lean mass preserved, p=0.001). Body composition shifted from 70% fat/30% lean with tirzepatide alone to 85%/15% with the combination. SRK-439 next-gen selective myostatin inhibitor is in preclinical development with attenuation of fat-mass rebound after GLP-1 withdrawal as a key signal.
Regeneron's COURAGE Phase 2 data presented at EASD 2025 continue to drive obesity-pipeline conversations. Semaglutide alone produced 6.5% lean mass loss at 26 weeks; sema + trevogrumab 200 mg cut that to 3.3% (~half), and the triplet with garetosmab (anti-activin A) pushed to 2.0% lean mass loss with 92.6% fat-mass loss. The triplet had higher discontinuation for tolerability. Full COURAGE completion is expected late 2026, with Phase 3 initiation likely 2027.