8-K: Scholar Rock's Apitegromab Demonstrates Significant Lean Mass Preservation in Obesity Trial, Bolstering Pipeline

Scholar Rock Holding Corporation announced positive Phase 2 EMBRAZE clinical trial data for apitegromab, demonstrating statistically significant preservation of lean mass during tirzepatide-induced weight loss.

Summary

• The Phase 2 EMBRAZE proof-of-concept trial assessed apitegromab in combination with tirzepatide to preserve lean mass during tirzepatide-induced weight loss in patients with obesity or overweight.
• The trial successfully achieved its primary endpoint, demonstrating statistically significant preservation of lean mass.
• Patients receiving apitegromab with tirzepatide over 24 weeks showed a 54.9% preservation of lean mass, equivalent to an additional 4.2 pounds (1.9 kilograms) of lean mass, compared to tirzepatide alone (p=0.001).
• For patients on tirzepatide alone, 30.2% of total weight loss was attributed to lean mass loss, whereas with apitegromab, this was reduced to 14.6%.
• A higher quality of weight loss was observed for patients receiving apitegromab with tirzepatide (85.3% fat mass / 14.6% lean mass) compared to tirzepatide alone (69.5% fat mass / 30.2% lean mass).
• Patients receiving apitegromab with tirzepatide lost 18.8 lbs of fat mass and 12.3% of body weight, while those on tirzepatide alone lost 17.7 lbs of fat mass and 13.4% of body weight.
• Apitegromab was generally well tolerated, and its safety profile was consistent with observations in prior clinical studies, with no serious adverse events or discontinuations related to apitegromab treatment.

Sentiment

Score: 9

Explanation: The document reports highly positive, statistically significant clinical trial results for a key product candidate in a large and growing market (obesity), addressing a known side effect of popular GLP-1 drugs. It also confirms strong progress on other pipeline assets and regulatory timelines, indicating robust development and commercialization prospects.

Positives

• Apitegromab achieved its primary endpoint in the Phase 2 EMBRAZE trial, demonstrating statistically significant preservation of lean mass (+4.2 lbs or 54.9% vs. tirzepatide alone, p=0.001).
• The combination therapy resulted in a higher quality of weight loss, with 85.3% of total mass loss from fat mass compared to 69.5% for tirzepatide alone.
• Apitegromab exhibited an encouraging safety profile, consistent with prior studies, with no serious adverse events or discontinuations attributed to the drug.
• The company remains on track for the anticipated commercial launch of apitegromab for Spinal Muscular Atrophy (SMA) in the US in Q4 2025, with a PDUFA date of September 22.
• Progress is being made on SRK-439, a novel subcutaneous anti-myostatin antibody, with an IND submission anticipated in the second half of 2025 for first-in-human studies, showing significant lean mass increase in preclinical nonhuman primate studies.

Risks

• Preclinical and clinical data, including results from the Phase 3 SAPPHIRE trial, may not be sufficient to support regulatory approval.
• Results from the Phase 2 EMBRAZE trial may not be predictive of, inconsistent with, or less favorable than data generated from future or ongoing clinical trials of the same product candidate.
• Scholar Rock's ability to manage expenses or provide the necessary financial support, resources, and expertise to identify and develop product candidates on the expected timeline.
• Information provided or decisions made by regulatory authorities could impact development and approval timelines.
• Competition from third parties developing products for similar uses poses a market risk.
• Scholar Rock's ability to obtain, maintain, and protect its intellectual property is crucial for its business.
• Dependence on third parties for the development and manufacture of product candidates, including supply for clinical trials, introduces operational risks.
• The company's ability to obtain additional funding when needed to support its business activities.
• The ability to establish or maintain strategic business alliances.
• The ability to receive priority or expedited regulatory review or to obtain regulatory approval of apitegromab.
• Risks associated with expanding globally and the anticipated commercial launch timing in the US and Europe.

Future Outlook

Scholar Rock plans to prepare for the commercial launch of apitegromab, pending potential approval in Spinal Muscular Atrophy (SMA), and intends to study it in a range of other neuromuscular diseases with high unmet need. The company anticipates filing an IND application for SRK-439, a subcutaneous anti-myostatin antibody, in the second half of 2025 to support its first-in-human study, exploring its potential in various rare, severe debilitating neuromuscular disorders. Scholar Rock expects a US commercial launch of apitegromab in Q4 2025 (PDUFA Sept 22) and an MAA filing in Europe by mid-2026, with continued global expansion efforts.

Management Comments

• Akshay Vaishnaw, M.D., Ph.D., President of R&D, stated: "We are pleased that the EMBRAZE trial accomplished its objective by achieving its primary endpoint. The results validated our hypothesis that our platform of highly selective myostatin inhibitors has the potential to support healthier weight loss for millions of patients on GLP therapies by safely preserving lean mass."
• Dr. Vaishnaw also added: "While this is an exciting development for our platform, we remain focused on preparing for the launch of apitegromab, and following its potential approval in SMA, we look forward to studying it in a range of neuromuscular diseases with high unmet need. Further, there is great potential with SRK-439 to be a subcutaneous, anti-myostatin antibody and we look forward to also exploring its potential in various rare, severe debilitating neuromuscular disorders. We remain on track to file an IND application for SRK-439 in the second half of this year to support the first in human study."

Industry Context

The announcement positions Scholar Rock's apitegromab as a potential adjunctive therapy to GLP-1 agonists like tirzepatide, which are highly effective for weight loss but are known to cause significant lean muscle mass loss. This addresses a critical unmet need in the rapidly growing obesity and cardiometabolic disorders market, offering a 'higher quality' weight loss by preserving muscle. The company also maintains its focus on Spinal Muscular Atrophy (SMA) and other neuromuscular diseases, where apitegromab is a leading muscle-targeted treatment candidate, and is advancing SRK-439, another anti-myostatin antibody, into preclinical development for similar indications.

Comparison to Industry Standards

• The document highlights that GLP-1 therapies, such as tirzepatide, can result in substantial loss of lean muscle mass, citing data from the SURMOUNT-1 study.
• In the SURMOUNT-1 study, pooled tirzepatide (5, 10, and 15 mg) resulted in a mean change from baseline in lean mass of -5.6 kg at Week 72, compared to -1.2 kg for placebo.
• In the EMBRAZE trial, tirzepatide alone led to a mean lean mass loss of -3.5 kg (-7.6 lbs) over 24 weeks, with 30.2% of total weight loss being lean mass.
• In contrast, apitegromab combined with tirzepatide resulted in a mean lean mass loss of only -1.6 kg (-3.4 lbs) over 24 weeks, with only 14.6% of total weight loss being lean mass, demonstrating a significant improvement in body composition compared to tirzepatide monotherapy and addressing a known limitation of current GLP-1 treatments.

Stakeholder Impact

• Shareholders: Likely positive impact due to successful clinical trial results, opening a potential new market for apitegromab in obesity, and continued progress on the existing SMA pipeline, suggesting increased future revenue potential.
• Patients with Obesity/Overweight: Potential for a healthier weight loss experience by mitigating lean muscle mass loss associated with GLP-1 therapies like tirzepatide.
• Patients with Spinal Muscular Atrophy (SMA) and other Neuromuscular Diseases: Continued development and potential approval of apitegromab and SRK-439 offer new therapeutic options to address muscle atrophy and weakness.
• Healthcare Providers: A new therapeutic option to address a significant side effect of widely used GLP-1 therapies, potentially improving patient outcomes and quality of life.

Next Steps

• Additional data from the EMBRAZE trial will be presented at upcoming medical congresses.
• Scholar Rock will host an investor conference call on June 18, 2025, at 8:00 AM EDT.
• Prepare for the commercial launch of apitegromab for Spinal Muscular Atrophy (SMA), pending potential regulatory approval.
• Study apitegromab in a range of neuromuscular diseases with high unmet need.
• File an IND application for SRK-439 in the second half of 2025 to support the first-in-human study.
• Explore SRK-439's potential in various rare, severe debilitating neuromuscular disorders.
• Execute successful commercial launch of apitegromab in the US (PDUFA Sept 22, Q4 2025).
• Advance launch preparedness for apitegromab in Europe (MAA mid-2026).
• Expand globally.

Key Dates

Recommendation

Keywords

Scholar Rock, apitegromab, EMBRAZE trial, Phase 2, obesity, lean mass preservation, tirzepatide, myostatin inhibitor, GLP-1 therapies, neuromuscular diseases, SMA, spinal muscular atrophy, SRK-439, biopharmaceutical, clinical trial data, weight loss, fat mass, muscle preservation