GLP-1s Erase 7.4% Muscle: The $7B Anti-Myostatin Fix Ranked

Everyone owns the GLP-1 drugs. Nobody owns the fix for their biggest side effect.

That is the setup in the anti-myostatin trade, and it is an under-covered corner of the entire obesity boom. Novo Nordisk’s semaglutide and Eli Lilly’s tirzepatide are redefining weight loss, but a large share of the pounds they remove is not fat. Across the major GLP-1 trials, 25% to 40% of total weight loss comes from lean muscle mass. In the Phase 2 BELIEVE study, semaglutide 2.4 mg produced a 7.4% decline in total body lean mass at 72 weeks. For a 65-year-old with limited muscle reserve, that is the difference between functional independence and a fall.

The market has already priced the GLP-1 winners. Lilly (LLY) is worth $1.05 trillion. The second-order trade, the companies fixing the muscle loss the GLP-1s create, is where the multiples are still sane. Here is the race, ranked by risk-reward, with prices from Polygon’s August 29 close.

The biology is simple enough to state in one paragraph. Myostatin and activin A are members of the TGF-beta family that act as brakes on muscle growth. Block the brake, and muscle builds. Scholar Rock’s apitegromab binds the pro and latent forms of myostatin. Regeneron’s trevogrumab blocks GDF8/myostatin directly and pairs it with garetosmab, which blocks activin A. Lilly’s bimagrumab blocks the activin type II receptor that both signals through. Veru’s enobosarm is different: it is a SARM, a selective androgen receptor modulator, not an antibody. The mechanisms vary. The goal is the same. Keep the muscle while the GLP-1 strips the fat.

Scholar Rock Apitegromab: The Only Near-Term Catalyst

Scholar Rock (SRRK) is the purest expression of the trade and the only name with an FDA decision on the calendar. Apitegromab is an anti-myostatin antibody for spinal muscular atrophy, and its Phase 3 SAPPHIRE trial was the first muscle-targeted drug ever to hit a primary endpoint in SMA. The trial met its goal with a 1.8-point improvement on the Hammersmith Functional Motor Scale Expanded versus placebo (p=0.0192). Some 30.4% of apitegromab patients gained at least 3 points on the HFMSE versus 12.5% on placebo. The results were published in The Lancet Neurology, and the trial is registered as NCT05156320.

The PDUFA date is September 30, 2026. Scholar Rock is prepared to launch immediately, and the stock has already rerated from the teens to $57.80, a $7.04 billion market cap, ahead of the decision.

The catch is manufacturing, not efficacy. On August 7, 2026, Scholar Rock disclosed that the FDA classified an April inspection of its Catalent Indiana fill-finish facility as Official Action Indicated, and it is pivoting to a second U.S.-based facility that is in good standing. That is the specific risk heading into September 30: a clean approval could still be delayed if the agency wants the manufacturing question fully resolved first. The approved drug with a slow launch is still preferable to the unapproved one, but this is a real, named risk, not a generic one.

Eli Lilly Bimagrumab: The $1.9B Anchor That Stepped Back

Lilly bought Versanis Bio for $1.9 billion in 2023 to get bimagrumab, and the Phase 2 BELIEVE data published in Nature Medicine is the benchmark for the whole space. The high-dose combination of bimagrumab 30 mg/kg plus semaglutide 2.4 mg produced 22.1% weight loss at 72 weeks versus 15.7% for semaglutide alone. Critically, bimagrumab alone added 2.5% lean mass while semaglutide lost 7.4%. The fat-loss index, the share of weight loss that is actual fat, was 100% for bimagrumab and 92.2% for the combination versus 75.6% for semaglutide.

Then Lilly blinked. In September 2025 the company halted one of its two Phase 2b trials of bimagrumab plus tirzepatide, the one enrolling type 2 diabetics, citing “strategic business reasons.” The FDA has signaled that improving muscle composition may not be enough on its own; the agency appears to want a functional benefit or additive weight loss. Bimagrumab is not in Phase 3, and Lilly, at a $1.05 trillion market cap, will not move a single percent on this program either way. The anchor of the trade is a rounding error to its owner.

Regeneron Trevogrumab: The Best Data Nobody Can Trade

Regeneron (REGN) has the cleanest obesity-specific dataset after Lilly, and you cannot meaningfully trade it. The Phase 2 COURAGE trial paired semaglutide with trevogrumab with or without garetosmab. Regeneron confirmed that 33% of semaglutide-induced weight loss is lean mass, and that adding trevogrumab prevented about half of that loss. At 26 weeks, the triple combination of semaglutide plus both antibodies produced a 27.1% fat reduction with only a 2.0% lean loss, versus 15.7% fat and 6.5% lean for semaglutide alone. That is the pharmacologically ideal profile.

The problem is the same one Lilly has. Regeneron is an $81.8 billion company where a muscle-sparing obesity add-on, even if it works, is a small fraction of a franchise built on Eylea and Dupixent. The COURAGE data is a signal for where the field is headed, not a stock catalyst.

Biohaven Taldefgrobep: A Pivot, Not a Pipeline

Biohaven (BHVN) is the cautionary tale in the muscle shelf. Its myostatin inhibitor taldefgrobep alfa missed the primary endpoint in the Phase 3 RESILIENT SMA trial, failing to statistically separate from placebo plus standard of care at 48 weeks. The stock fell 10% on the news. Biohaven is now recasting taldefgrobep for obesity, the GLP-1 muscle-preservation angle, but that is a reset, not a readout. At $15.41 and a $2.33 billion market cap, BHVN is a show-me story. The myostatin mechanism clearly works in the right patient and trial design, which SAPPHIRE proved and RESILIENT did not; the difference was the endpoint and population, not the biology. A failed SMA asset on a promise to re-file it in obesity is not worth buying.

Veru Enobosarm: A $45M Lottery Ticket

Veru (VERU) is the smallest name on the list, and it is not really an anti-myostatin play. Enobosarm is an oral SARM that showed a 59.8% relative reduction in the share of patients losing 10% or more of stair-climb power in the Phase 2b QUALITY study with semaglutide (p=0.0006). That is a functional endpoint, which is exactly what the FDA wants. But Veru carries a $44.8 million market cap and is still preparing its Phase 3 program with a reformulated version. This is a binary lottery ticket, and at this valuation the market is pricing in near-certain dilution before any Phase 3 data. A 1% position at most, and only if you accept it could go to zero.

The Verdict

The anti-myostatin trade splits into two end-markets with very different risk profiles. The neuromuscular market, where apitegromab lives, is a $7 billion company with a September 30 PDUFA and a demonstrated, peer-reviewed Phase 3 win. The obesity market is bigger, but it is owned by mega-caps where the drug is immaterial, and the pure-play names are either a failed asset looking for a second act (Biohaven) or a micro-cap lottery ticket (Veru).

Scholar Rock is the only buyable way to own this theme with a catalyst inside 30 days, in the same muscle-disease neighborhood Sarepta built its DMD franchise in. Size it for the binary: the SAPPHIRE data supports approval, but the Catalent manufacturing disclosure means a delay is a live possibility. Hold the name through September 30 if you already own it. If you are looking for the second-order GLP-1 trade, the honest answer is that the real money is still 18 to 24 months away, and it will land with Regeneron’s COURAGE program or a partnered Lilly asset, not with a small cap you can front-run today.