FDA Approves Drug for Rare Muscle Disorder

The US Food and Drug Administration (FDA) today approved deflazacort (Emflaza/Marathon Pharmaceuticals) an orphan drug used to treat patients five years and older for Duchenne muscular dystrophy (DMD). The ailment is a rare genetic disorder that causes progressive muscle deterioration and weakness. Emflaza is a corticosteroid that works by decreasing inflammation and reducing the activity of the immune system.

Corticosteroids are commonly used to treat DMD across the world. This is the first FDA approval of any corticosteroid to treat DMD and the first approval of deflazacort for any use in the United States.

The effectiveness of deflazacort was shown in a clinical study of 196 male patients who were 5 to 15 years old at the beginning of the trial with documented mutation of the dystrophin gene and onset of weakness before age five. At week 12, patients taking deflazacort had improvements in a clinical assessment of muscle strength across a number of muscles compared to those taking a placebo. An overall stability in average muscle strength was maintained through the end of study at week 52 in the deflazacort-treated patients. In another trial with 29 male patients that lasted 104 weeks, deflazacort demonstrated a numerical advantage over placebo on an assessment of average muscle strength. In addition, although not statistically controlled for multiple comparisons, patients on deflazacort appeared to lose the ability to walk later than those treated with placebo.

The side effects are similar to those experienced with other corticosteroids. The most common side effects include facial puffiness (Cushingoid appearance), weight gain, increased appetite, upper respiratory tract infection, cough, extraordinary daytime urinary frequency (pollakiuria), unwanted hair growth (hirsutism) and excessive fat around the stomach (central obesity).

DMD is the most common type of muscular dystrophy. DMD is caused by an absence of dystrophin, a protein that helps keep muscle cells intact. The first symptoms are usually seen between three and five years of age and worsen over time. The disease often occurs in people without a known family history of the condition and primarily affects boys, but in rare cases it can affect girls. DMD occurs in about one of every 3,600 male infants worldwide.

People with DMD progressively lose the ability to perform activities independently and often require use of a wheelchair by their early teens. As the disease progresses, life-threatening heart and respiratory conditions can occur. Patients typically succumb to the disease in their 20s or 30s; however, disease severity and life expectancy vary.

Other side effects that are less common include problems with endocrine function, increased susceptibility to infection, elevation in blood pressure, risk of gastrointestinal perforation, serious skin rashes, behavioral and mood changes, decrease in the density of the bones and vision problems such as cataracts. Patients receiving immunosuppressive doses of corticosteroids should not be given live or live attenuated vaccines.

The FDA granted this application fast track designation and priority review. The drug also received orphan drug designation, which provides incentives to assist and encourage the development of drugs for rare diseases.

The sponsor is receiving a rare pediatric disease priority review voucher under a program intended to encourage development of new drugs and biologics for the prevention and treatment of rare pediatric diseases. A voucher can be redeemed by a sponsor at a later date to receive priority review of a subsequent marketing application for a different product. This is the ninth rare pediatric disease priority review voucher issued by the FDA since the program began.