Pharma

FDA approves Duchenne muscular dystrophy drug

The FDA has given the green light to Emflaza (deflazacort), a new drug for Duchenne muscular dystrophy. Announced Thursday, the news is bittersweet. Deflazacort is a corticosteroid, a class of drugs that doctors have used off-label for many years.

FDA APPROVED

The U.S. FDA has given the green light to Marathon Pharmaceuticals’ Emflaza (deflazacort), a new treatment for Duchenne muscular dystrophy (DMD).

Announced Thursday, the news could be bittersweet for patients and caregivers.

While it has shown efficacy, Emflaza is a corticosteroid — part of a class of drugs that are already widely used for DMD. Emflaza will be the first on-label drug, however, as none have been directly approved for this condition.

Emflaza also marks the first approval of deflazacort in the U.S. The drug was approved in the U.K. in 2008, where it is now sold as Calcort.

Despite the incremental nature of the drug approval, the Muscular Dystrophy Association was rejoicing over the win.

“Emflaza has shown meaningful benefits for patients living with DMD and has the potential to delay disease progression,” stated EVP, CMO and CSO Valerie Cwik in an early press release forwarded via email. “With the FDA approval of Emflaza, we now have a treatment option for kids and adults with Duchenne, which is a major advance for the community. As a physician, I participated in a clinical trial of Emflaza and have a keen awareness about what the approval of this drug means for patients and families.”

Globally, DMD affects around one in every 3,600 male infants, making it the most common form of muscular dystrophy. It is caused by a mutated gene on the X chromosome. Males who inherit the mutation from a ‘carrier’ mother develop the disease. (Females have a second X chromosome, which compensates for the defect.)

The disease-causing mutation interferes with the production of a protein called dystrophin. Without dystrophin, the patient’s muscle cells are fragile and easily damaged. DMD symptoms usually appear between 2-6 years of age. Over time the muscles degenerate, causing a progressive weakening.

Corticosteroids, such as Emflaza, work to decrease inflammation and activation of the immune system.

In a 196-person trial, patients on Emflaza showed an improvement in strength across a number of muscle groups compared to those taking a placebo. The patients in the active arm also demonstrated an overall stability in average muscle strength throughout the 52-week study. In a second 104-week trial with 29 patients, deflazacort demonstrated a numerical advantage over placebo on an assessment of average muscle strength.

There was some evidence to suggest patients taking Emflaza lost the ability to walk later than those treated with placebo, though this was not statistically controlled for.

As with other corticosteroids, Emflaza comes with a suite of side effects, including facial puffiness, weight gain, increased appetite, upper respiratory tract infection, cough, extraordinary daytime urinary frequency, unwanted hair growth and excessive fat around the stomach. Other less common side effects can also occur.

On the flipside, Emflaza is broad-acting and works for all subtypes of the disease, irrespective of the underlying mutation.

Marathon Pharmaceuticals swept up a trifecta of FDA special treatments for this drug, including fast track designation, priority review and orphan drug designation. They will also receive a rare pediatric disease priority review voucher to encourage further R&D in rare pediatric diseases.

In September 2016, a disease-modifying drug from Sarepta was provisionally approved by the FDA. Dubbed Exondys 51, it has been priced at $300,000 per year, despite controversially minimal improvements in patient outcomes.

Earlier that year, the agency rejected a DMD therapy developed by BioMarin Pharmaceuticals after a panel of independent advisers concluded that the drug, Kyndrisa, had not demonstrated any measurable efficacy.

With just one targeted treatment on the market, the bar is set low for DMD. Emflaza may offer some real value in the coming years, but a big breakthrough is still very much needed.

Photo: bandit2523, Getty Images

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