SRRK Stock Soars as Muscle Disease Drug Meets Phase III Study Goal

Core Viewpoint - Scholar Rock's shares surged 362% following the announcement of positive results from the late-stage study of apitegromab for treating spinal muscular atrophy (SMA) [1] Company Overview - Scholar Rock is focused on developing apitegromab, a fully human monoclonal antibody that inhibits myostatin activation, which is crucial for muscle growth regulation [2] - The company has seen an 82.3% increase in shares year-to-date, contrasting with a 2.8% decline in the industry [7] Clinical Study Results - The phase III SAPPHIRE study met its primary endpoint, showing a statistically significant improvement in motor function in SMA patients treated with apitegromab compared to placebo at week 52, measured by the Hammersmith Functional Motor Scale Expanded (HFMSE) [3] - In the main efficacy group (ages 2-12), 30% of patients on apitegromab achieved a 3-point or more improvement in HFMSE, compared to 12.5% in the placebo group [4] - Early motor function gains were observed as soon as eight weeks into treatment, with continued improvement at 52 weeks [5] Safety Profile - Apitegromab was well-tolerated across all age groups, with no significant differences in adverse events between the two dosage strengths (10 mg/kg and 20 mg/kg) [7] - Serious adverse events were not attributed to apitegromab, and no patients discontinued the study due to adverse events [7] Regulatory and Future Plans - Scholar Rock plans to submit regulatory applications for apitegromab in the U.S. and EU in Q1 2025, with existing designations such as Fast Track and Orphan Drug in the U.S. and Priority Medicines in the EU [8] - Detailed data from the SAPPHIRE study is expected to be presented at a medical conference in early 2025 [9] Other Developmental Programs - Scholar Rock is also evaluating apitegromab for cardiometabolic disorders, with a phase II EMBRAZE study completed for preserving lean muscle mass in individuals on GLP-1 receptor agonist therapy [10] - The company is advancing SRK-439, a selective myostatin inhibitor, for treating cardiometabolic disorders [11] - Another candidate, SRK-181, is in a phase I study for advanced cancer treatment [12] Market Impact - Following Scholar Rock's positive data, Biohaven's stock rose 10.8%, as investors anticipate favorable results from its own SMA study [13] - Biohaven is evaluating taldefgrobep alfa (BHV-2000) in a phase III study for SMA, with top-line data expected by the end of 2024 [14]