Pfizer's Phase 3 DMD Miss No Threat to Sarepta's Elevidys: Analysts

Pfizer's recent phase 3 trial failure for its Duchenne muscular dystrophy (DMD) gene therapy has further solidified Sarepta Therapeutics' position as the leading company in the DMD market with its Elevidys therapy. On Wednesday, Pfizer revealed that its gene therapy, fordadistrogene movaparvovec, failed to show improvement in motor function among DMD patients aged 4 to 7 in a phase 3 study. Additionally, the therapy did not achieve any secondary endpoints or demonstrate a significant difference compared to a placebo. Pfizer must now reassess the future of this program.

This setback follows a fatal incident in a phase 2 trial of younger patients, where a boy died of cardiac arrest in May after receiving the therapy. The recent phase 3 trial employed a crossover design, but dosing associated with the crossover was halted following the fatality. Analysts at Leerink believe the lack of efficacy and safety concerns make it unlikely that Pfizer's program will proceed further, describing the recent trial results as the "final nail in the coffin."

William Blair analysts have long doubted the competitiveness of Pfizer's program against Sarepta's Elevidys. They believe the recent phase 3 failure effectively removes Pfizer from the competitive landscape, especially as Sarepta nears an FDA decision for a key label expansion. Sarepta is expected to receive news on June 21 regarding a potential broader label and conversion to full approval for Elevidys. Since its initial approval last June, Sarepta has aimed for a label that covers the treatment of all DMD patients with a confirmed mutation in the DMD gene. CEO Douglas Ingram has described this as the "broadest possible label."

Currently, Elevidys is approved for treating ambulatory patients ages 4 to 5, a narrow demographic presenting several executional challenges. As the average age of DMD diagnosis in the U.S. is 5, many patients in the approved age range are not yet diagnosed, creating a "race against time" to secure access to Elevidys before patients age out of eligibility. Despite missing the primary endpoint in one of its phase 3 studies, analysts at William Blair believe that the overall data supports Elevidys' conversion to full approval and broader expansion.

However, treating non-ambulatory patients remains uncertain; analysts predict these patients might be excluded from the expanded label. Sarepta is steadily navigating through its relatively small pool of eligible patients. Since Elevidys' approval in June 2023, the company has generated $200.4 million in sales last year and $133.9 million in the first quarter of this year.

The recent developments illustrate the tumultuous journey of gene therapies in the DMD field. While Pfizer grapples with significant setbacks, Sarepta is poised to strengthen its leadership position, contingent upon regulatory decisions that could potentially expand its market. As the landscape for DMD treatments evolves, the upcoming FDA decision will be crucial for Sarepta’s future strategy and patient access to Elevidys.