Phase 3 Trial Results Look Promising for Potential Duchenne MD Therapy Deflazacort

Results from a Phase 3 clinical trial comparing deflazacort and prednisone, two corticosteroid drugs under evaluation as potential treatments for Duchenne muscular dystrophy, showed that both deflazacort and prednisone improved muscle strength compared to a placebo, meeting the primary endpoint of the study. But deflazacort caused less weight gain than prednisone, according to Marathon Pharmaceuticals, which is developing deflazacort.

The research paper detailing the results, “Efficacy and safety of deflazacort vs prednisone and placebo for Duchenne muscular dystrophy,” was recently published in the journal Neurology.

The trial evaluated the safety and effectiveness of deflazacort and prednisone compared to a placebo. The study followed 196 patients, ages 5 to 15, who were randomly assigned to one of four groups: deflazacort (0.9 mg/kg/day); deflazacort (1.2 mg/kg/day); prednisone (0.75 mg/kg/day); and a placebo. After 12 weeks, the placebo participants were randomly assigned to one of the treatment groups, and all patients were followed for 52 weeks.

The results showed that after 12 weeks, both drugs showed significant improvement in muscle strength compared with the placebo, but deflazacort caused fewer side effects than prednisone, such as weight gain. Also, patients who received the lower dose of deflazacort presented a significant improvement in average muscle strength score at week 52 compared with the prednisone group.

“Corticosteroids are the only treatment that increases muscle strength in boys with Duchenne muscular dystrophy,” said Dr. Robert Griggs, MD, lead author of the study and professor in the Department of Neurology of the University of Rochester, in a news release. “With currently no FDA-approved treatment for Duchenne and no cure, deflazacort may provide an important treatment option for delaying the progression of Duchenne.”

The three most commonly reported treatment-related adverse events in all groups were Cushingoid appearance (69.4 percent), erythema (41.8 percent), and hirsutism (39.3 percent). The side effects associated with long-term steroid use were not evaluated, given the study’s duration of 52 weeks.

In addition to this study, Marathon conducted eight other clinical pharmacology and safety studies and nine preclinical studies for the use of deflazacort.

Marathon has now proposed two new drug applications (NDAs) for deflazacort, one for the production of a tablet to be immediately released (6 mg, 18 mg, 30 mg, and 36 mg) and the other for the production of an oral suspension (22.75 mg/mL) formulation.

According to Marathon, both NDAs are now under consideration by the U.S. Food and Drug Administration (FDA).

“As with too many rare diseases, patients and families living with Duchenne muscular dystrophy have limited treatment options and a dire need for reliable therapies,” said Tim Cunniff, Marathon’s executive vice president of research and development at Marathon.

“These very encouraging data underscore the merits of bringing deflazacort through the FDA review process in the hopes of making deflazacort broadly available to patients who could benefit from it in the U.S.”

Deflazacort and prednisone are corticosteroid drugs with an anti-inflammatory and immunosuppressant action. Deflazacort is marketed in other countries for several indications. If approved, it will be among the first available treatments for this disease in the U.S.