An old steroid used to treat a rare disease just got approved by the FDA - and it costs $89,000

The FDA on Thursday approved a drug to treat Duchenne muscular dystrophy (DMD), a devastating muscle-wasting disease that mainly affects young boys.

The drug, Emflaza, known generically as deflazacort, belongs to a class of anti-inflammatory drugs known as corticosteroids that are frequently used to treat DMD and other conditions.

Emflaza is the first steroid to win formal FDA approval to treat DMD. Prednisone, another steroid, is frequently prescribed for the disease though it does not have official FDA approval. Emflaza is thought to have fewer side effects than Prednisone.

While this is the first time the FDA has approved deflazacort, the steroid has been available outside the US for decades. Marathon, the company that owns Emflaza, did not invent deflazacort, and patients have been able to import it cheaply for for years since it hadn't been approved in the US.

That will now change. Patients will no longer be allowed to import the drug now an FDA-approved product is available. Instead, the drug will carry a list price of $89,000 a year, though the company said it will provide a "robust" assistance program for patients who are not covered by insurance.

The move is reminiscent of a plan former pharma CEO Martin Shkreli had with a treatment for another rare disease. While CEO of KaloBios, Shkreli had told investors that he planned to price a drug called benznidazole that's used to treat the neglected parasitic infection Chagas disease somewhere in the $60,000-to-$100,000 per-treatment range. The decades-old drug hasn't been approved in the US, but it's used around the world and provided in specific instances to the US for free.

Marathon will also get a priority review voucher, which are granted to companies who develop treatments for neglected diseases as a way to add incentives on drugs that otherwise wouldn't have much commercial value.

The voucher can then be used by the company to speed up its review time for another drug, or it can be sold to another company that wants to fast-track its drug by a few months. These vouchers have been sold for up to $350 million.

Duchenne's is a rare genetic disorder affecting some 15,000 U.S. patients that causes progressive muscle deterioration and kills most sufferers by the age of 30. Last year Dr. Janet Woodcock, head of the FDA's pharmaceuticals division, ordered the approval of a Duchenne drug made by Sarepta Therapeutic despite opposition from the agency's top scientists and a negative recommendation from a panel of outside advisors.

The FDA approved Emflaza for all DMD patients five years and older. Sarepta's drug treats a subset of DMD patients representing about 13% of the total.

Reuters reporting by Toni Clarke.