As New Duchenne Therapy Enters Phase 1 Trial, Advocacy Groups Seek Better Access to Existing Drug

Pfizer has dosed its first patient in a phase 1 clinical trial of an investigational gene therapy for the treatment of patients with Duchenne muscular dystrophy (DMD), a rare genetic disease that results in the absence of dystrophin, a protein that helps to keep muscle cells intact. DMD primarily affects males and is characterized by progressive muscle degeneration and weakness that can lead to early death.

The therapy, PF-06939926, is a recombinant adeno-associated virus capsid carrying a truncated version of the human dystrophin gene under the control of a human muscle-specific promotor.

Enrollment in the multicenter, open-label, nonrandomized ascending dose study is expected to continue at up to 4 research sites in the United States, and early data are expected in the first half of 2019. The study will enroll approximately 12 patients with DMD, aged 5 to 12 years, and will evaluate the safety and tolerability of the drug, dystrophin expression and distribution, and patients’ muscle strength, quality, and function.

“Investment in this trial represents the culmination of years of research on behalf of patients by scientists at Pfizer and academic medical centers, along with the support of the DMD patient advocacy community, in the important quest to advance a program that could potentially change the trajectory of this debilitating disease,” said Greg LaRosa, PhD, senior vice president and chief scientific officer of Pfizer’s rare disease research unit, in a statement.

Current treatments for DMD include the use of corticosteroids and eteplirsen (Exondys 51), a injected drug that promotes dystrophin production by restoring the translational reading frame of the DMD gene through specific skipping of exon 51 in defective gene variants. The drug is applicable for approximately 14% of patients with DMD.

While eteplirsen, currently the only FDA-approved treatment for DMD, has been hailed by patient groups as an important step forward, the drug can cost as much as $1.5 million per patient per year.

As a result of the limited patient access that results from such a high price tag, 6 advocacy organizations, including Patients for Affordable Drugs and Universities Allied for Essential Medicines, asked HHS Secretary Alex Azar in an April 5, 2018, letter to exercise HHS’ rights to take ownership of 5 patents covering eteplirsen, and to use ownership as a way to bring down the cost of the drug for patients. According to the letter’s authors, because the government had a role in funding the research that allowed drug maker Sarepta Therapeutics to develop the therapy—and because researchers did not disclose that federal funding—HHS has the right to impose sanctions on Sarepta.