Sarepta Drops 42% on Fatalities; Markets Eye Solid Biosciences

Sarepta Therapeutics' stock plunged over 40% following a second patient death linked to acute liver failure after treatment with its Duchenne muscular dystrophy (DMD) gene therapy, ELEVIDYS, prompting the suspension of shipments for non-ambulatory patients and withdrawn revenue guidance; ELEVIDYS accounted for 61% of Sarepta's total revenue last quarter. Solid Biosciences, developing a potentially safer DMD alternative, saw its shares jump over 11%, as investors speculate STG-003 could gain traction, though both companies remain high-risk investments. While Sarepta will continue selling ELEVIDYS to ambulatory patients and hopes for FDA approval of an enhanced safety regime, Solid Biosciences is planning to meet with the FDA in Q4 2025 to discuss STG-003.

Analysis

Sarepta Therapeutics (SRPT) experienced a significant setback following a second patient death due to acute liver failure linked to its Duchenne muscular dystrophy (DMD) treatment, ELEVIDYS, resulting in a stock plunge of over 42% on June 16. This event prompted the company to suspend ELEVIDYS shipments for non-ambulatory patients and withdraw its revenue guidance. The impact is substantial, as ELEVIDYS accounted for 61% of Sarepta's $612 million total revenue last quarter, drove nearly all its growth with a 180% sales increase, and was central to a previously forecasted $2.3 billion to $2.6 billion in 2025 sales. However, Sarepta will continue selling ELEVIDYS to ambulatory patients, who have historically constituted 85% of patients dosed (70% in 2025), a segment the company believes can maintain profitability. Sarepta is developing an enhanced regimen to mitigate liver failure risk, pending FDA approval, with hopes for a guidance update during its Q2 earnings call; analysts maintain a consensus price target around $70, implying significant upside, likely reflecting the ongoing ambulatory sales. Concurrently, Solid Biosciences (SLDB) saw its shares jump over 11% as investors speculate its DMD candidate, STG-003, could emerge as a safer alternative. Early trial data for STG-003 indicated high microdystrophin expression and a potentially more favorable liver safety profile compared to ELEVIDYS, which is known to elevate liver enzymes in approximately 30% of patients. Solid Biosciences plans to meet with the FDA in Q4 2025 to discuss an accelerated approval pathway for STG-003, though it remains an early-stage asset facing a long development road. Both companies represent high-risk investments, with their futures heavily dependent on clinical outcomes and regulatory decisions in the DMD gene therapy landscape.

Key Decisions for Investors

• Investors in Sarepta Therapeutics (SRPT) should closely monitor communications regarding the FDA's review of the enhanced ELEVIDYS regimen and await the Q2 earnings call for updates on revenue guidance and the timeline for resuming non-ambulatory sales, while acknowledging the substantial downside risk associated with any further adverse events despite continued sales to the ambulatory patient segment.
• For Solid Biosciences (SLDB), the recent positive momentum is speculative, tied to Sarepta's challenges and early STG-003 data; key catalysts to watch include the outcome of the planned Q4 2025 FDA meeting regarding accelerated approval and subsequent clinical trial results, understanding this remains a high-risk developmental-stage biotechnology investment.
• Given the binary nature of outcomes in DMD gene therapy development, positions in both SRPT and SLDB should be sized according to high-risk tolerance, with diversification strategies considered to mitigate idiosyncratic drug development risks.