Deflazacort (brand name, Emflaza; originally developed by Marathon Pharmaceuticals and later acquired by PTC Therapeutics) is a corticosteroid to treat people with Duchenne muscular dystrophy, ages 5 and older, regardless of disease-causing genetic mutation.

How does deflazacort (Emflaza) for DMD work?

Deflazacort is a corticosteroid precursor, which means that it is a substance from which an active corticosteroid, 21-desDFZ, is formed. It acts through the glucocorticoid receptor to exert anti-inflammatory and immunosuppressive effects.

The precise mechanism by which it works in people with DMD is not yet known.

Studies of deflazacort

The U.S. Food and Drug Administration’s (FDA) approval of Emflaza was based on a randomized, double-blind, and placebo-controlled clinical trial that took place in the U.S. and Canada. This  52-week study included 196 boys, ages 5 to 15, with DMD whether ambulatory or not.

In part 1, patients were given either deflazacort (0.9 or 1.2 mg/kg each day), a comparable corticosteroid (prednisone), or placebo for 12 weeks. In part 2, after those 12 weeks, the placebo group was given either deflazacort or the active comparator for 40 weeks. Participants already on an active treatment (either deflazacort or prednisone) continued on that treatment for those 40 weeks.

Average muscular strength was the trial’s efficacy measure, and the change in muscle strength was found to be significantly greater at week 12 in boys taking deflazacort (0.9 mg/kg each day) compared to placebo (no significant additional benefit was seen in the higher dose).  Muscle strength continued to increase through week 52 in this group, demonstrating persistence of the treatment’s beneficial effect.

Several assessments of the participants’ function (time to stand from supine, time to climb four stairs and time to walk or run 30 feet) also favored deflazacort (0.9 mg/kg) at week 12 compared to placebo.

Participants who were taking deflazacort also gained less weight than participants who were taking prednisone. The most frequent adverse events for all the participants on treatment were Cushingoid appearance, erythema, hirsutism, increased weight, headache and nasopharyngitis.

This Phase 3 study was completed in 1995, but results were only published in November 2016 (in the journal Neurologyas the original trial sponsor was purchased by another company who decided not to pursue its development in the U.S.

A more recent study (NCT02251600) in 29 DMD boys, ages 6 to 12, evaluated deflazacort in comparison to placebo for two years. Improvements recorded in muscle strength did not reach statistical significance, possibly because of a limited number of placebo-arm patients, but favored deflazacort treatment.

Further DMD studies planned by Marathon for Emflaza include a trial examining the safety and effectiveness of different dose regimens in younger patients, and a safety and efficacy study in non-ambulatory patients.

Indications and side effects

Emflaza is the first FDA-approved corticosteroid to treat all DMD patients, and the first approval of deflazacort for any use in the U.S.

Common side effects include facial puffiness or Cushingoid appearance, weight gain, increased appetite, upper respiratory tract infection, cough, frequent daytime urination, unwanted hair growth, central obesity, and colds.

People using Emflaza are not advised to be vaccinated with live or live-attenuated vaccines. New or booster vaccinations should be discussed first with a doctor.


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