Cambridge, Mass.– Scholar Rock (NASDAQ: SRRK) has announced encouraging topline results from its Phase 2 EMBRAZE trial, showing that its investigational therapy apitegromab, when combined with the weight-loss drug tirzepatide, significantly preserved lean muscle mass in adults with obesity or overweight conditions. The findings offer proof-of-concept that apitegromab, a selective myostatin inhibitor, can improve the quality of weight loss by maintaining muscle mass typically lost during GLP-1 therapy.
Over 24 weeks, participants receiving apitegromab with tirzepatide lost an average of 4.2 pounds less lean mass than those receiving tirzepatide alone—representing a 54.9% preservation of lean mass (p=0.001). Both groups lost a similar amount of fat mass (18.8 lbs vs. 17.7 lbs), but the combination therapy resulted in a higher proportion of fat-to-lean mass loss (85% fat vs. 70%), indicating a more favorable body composition outcome.
“These results reinforce our belief that preserving lean muscle is crucial during therapeutic weight loss, especially with the rise of GLP-1 drugs,” said Dr. Akshay Vaishnaw, President of R&D at Scholar Rock. “Our EMBRAZE study validates that highly selective myostatin inhibition via apitegromab can be a key adjunct in managing weight while protecting muscle health.”
The study included 87 patients with a BMI of 30 or higher (or 27+ with related comorbidities) and compared apitegromab plus tirzepatide to a placebo plus tirzepatide. All participants received treatment for 24 weeks. While both arms saw substantial weight loss—12.3% and 13.4% respectively—patients on apitegromab experienced a greater preservation of lean tissue and a higher quality of weight reduction overall.
Importantly, apitegromab was well tolerated, with no treatment-related serious adverse events or discontinuations. The safety profile remained consistent with previous studies of the drug.
Scholar Rock views these results as a potential expansion opportunity for apitegromab, which is primarily being developed for spinal muscular atrophy (SMA). The company also plans to explore additional neuromuscular indications through its pipeline, including its next-generation compound SRK-439, expected to enter clinical trials later this year.
