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Dive Brief:

• An experimental, muscle-preserving therapy from Scholar Rock succeeded in a Phase 3 trial in spinal muscular atrophy, positioning the biotechnology company to seek approvals in the U.S. and Europe early next year.

• A regimen of Scholar Rock’s drug, apitegromab, and a standard SMA therapy significantly improved motor function after one year versus treatment with a typical SMA medicine and a placebo, the company said Monday. Specifically, a prespecified, pooled analysis showed children between 2 and 12 years old who received one of two tested doses had an average difference versus placebo of about a 1.8-point change from baseline on a scale used to evaluate their physical abilities.

• Motor function benefits were also observed in a smaller, exploratory group of 13- to 21-year-olds, according to the company. No new safety findings were reported, and no one dropped out of the trial due to side effects. “We believe these data collectively show that apitegromab has the potential to become part of a new standard of care,” CEO Jay Backstrom said on a conference call. Shares more than quadrupled in value Monday.

Dive Insight:

Scholar Rock’s findings have implications not only for people with SMA, but for ongoing research into drugs designed to preserve muscle as well.

In SMA, apitegromab could further what’s already been a dramatic shift in treatment. Prior to 2016, there were no medicines available for SMA, a rare disease that causes progressive muscular weakness and in its most severe form can be lethal in infants. Since then, regulators have approved a gene-targeting medicine from Biogen, a gene therapy from Novartis and an oral treatment from Roche.

All three can change SMA’s course, helping babies survive when they may not have otherwise, hit growth milestones and avoid the use of a machine to help them breathe. But the therapies have “mixed” effects on motor function, analysts at the firm Piper Sandler wrote earlier this year. Specifically, long-term study results suggest that a treatment benefit “plateaus and wanes over time,” causing an overall decline that leaves room for a therapy that can improve function, they wrote in September.

Scholar Rock claims to have met that goal with apitegromab, which blocks a protein, myostatin, that can limit muscle growth. On a conference call, executives pointed to results showing how treatment with the drug, when added to either Biogen’s or Roche’s therapies, led to improved motor function early on and increased with time. Additionally, 30% of those on Scholar Rock’s drug had at least a three-point improvement on a ratings scale widely used to evaluate SMA therapies. By comparison, 12.5% of placebo recipients hit that mark.

The results “demonstrate the ability of apitegromab to alter the course of disease, from losing function to gaining function,” said Chief Medical Officer Jing Marantz, on the call.

Scholar Rock shares had lost more than half of their value this year amid skepticism apitegromab could help people already on other drugs, Jefferies analyst Michael Yee wrote on Monday. The study’s “surprise” success has reversed that trend and solidified Scholar Rock as an “attractive M&A acquisition candidate,” he added.

With the more than 300% stock jump Monday, Scholar Rock is now worth about $2.6 billion.

Analysts also think the findings could fuel optimism that the drug and others like it have a role in treating obesity. Scholar Rock is among a handful of companies, including Biohaven Pharmaceutical and Roche, testing whether myostatin-blocking therapies can preserve muscle in people taking popular weight loss drugs like Novo Nordisk’s Wegovy. Proof such drugs provide a benefit on top of other SMA treatments “is a major win for the anti-myostatin field and the SMA community writ large,” wrote Piper Sandler analyst Christopher Raymond.

Scholar Rock expects results from a Phase 2 study of apitegromab in obesity in the second quarter of 2025. Biohaven is developing a similar drug for SMA and obesity as well, and anticipates Phase 3 SMA results later this year.

Roche's anti-myostatin drug is in early-stage testing.