In combination with Eli Lilly’s tirzepatide, marketed as Zepbound for obesity, Scholar Rock’s monolonal antibody helped patients lose the same amount of weight as patients on tirzepatide alone while preserving more muscle mass.
When combined with Eli Lilly’s blockbuster weight loss drug tirzepatide, Scholar Rock’s monoclonal antibody apitegromab—which faces an upcoming PDUFA for its use in spinal muscular atrophy— preserves 55% more lean muscle mass than tirzepatide alone, the biotech announced early Wednesday.
That figure beats Scholar Rock’s own expectations. “The results are higher than initial management commentary of a 20-40% muscle preservation expectation,” analysts from Jefferies wrote in a note to investors.
The company’s stock was up about 15.5% after the markets opened Wednesday morning.
The data comes from Scholar Rock’s Phase II EMBRAZE trial, which met its primary endpoint of change in baseline in lean mass after 24 weeks.
BMO Capital Markets analysts also had a positive reaction to the news but pointed out that overall weight loss was no better than tirzepatide alone. Indeed, patients in the combination arm of the trial lost 8.5 kg versus 8.0 kg in the monotherapy arm. However, the combo treatment’s weight loss was 85% fat mass, while that for tirzepatide alone was 70% fat, the rest being in lean mass.
BMO added that the results are in line with a combination therapy Regeneron is testing: its own anti-myostatin antibody trevogrumab alongside Novo Nordisk’s semaglutide, marketed for weight loss as Wegovy. In Phase II data released two weeks ago, the combo therapy preserved 50–80% of lean mass lost with semaglutide alone. “Today’s results validate what we have seen with Regeneron’s recent COURAGE study,” Seigerman wrote.
Scholar Rock already has apitegromab on a priority review track for treating spinal muscular atrophy (SMA). The antibody blocks myostatin, an inhibitor of muscle growth. Through that mechanism, the company sees an opportunity to repurpose its drug for keeping muscle mass in patients on GLP-1s, where loss of muscle mass is a significant issue.
The highly anticipated PDUFA date for apitegromab in SMA is September 22. In October 2024 Scholar Rock released data from a Phase III trial that showed improvement in motor function in patients with SMA, sending the company’s stock soaring 300%.
The EMBRAZE results will also be a boost for the company’s next-generation anti-myostatin antibody SRK-439. Scholar Rock intends to file an IND for the drug in the second half of the year. The Jefferies analysts wrote that they “believe there’s ‘hidden value’ in the idea that SRK-439 . . . can be quickly developed into other rare neuromuscular disorders—not just obesity.”
