Uncertainties Over Effectiveness and High Costs Surround DMD Therapies

by Angela Maas

Since 2016, the FDA has approved a handful of therapies to treat Duchenne muscular dystrophy (DMD). But some uncertainty exists over their effectiveness, in addition to concerns about their costs.

When DMD is suspected, a blood test that measures creatine kinase (CK) levels is performed. "CK is an enzyme found in abnormally high levels when muscle is damaged," says Mesfin Tegenu, R.Ph., president of PerformRx, LLC. "The detection of an elevated CK level leads to molecular genetic testing to confirm a definitive diagnosis of DMD."

In February 2017, the FDA approved then-manufacturer Marathon Pharmaceuticals LLC's Emflaza (deflazacort). The company said it would be priced at $89,000, which sparked outrage since people have been buying a generic version from overseas since the 1990s for about $1,000 per year. After the backlash, Marathon ultimately sold the drug to PTC Therapeutics Inc., which launched it later that year with a $35,000 annual price tag. Since then, PTC has raised the price to more than Marathon’s original one.

In September 2016, the FDA gave accelerated approval to Sarepta Therapeutics, Inc.'s Exondys 51 (eteplirsen). The dystrophin gene has 79 exons, and about 80% of people with DMD have genotypes that are amenable to exon skipping. Exondys 51 targets those with a mutation of the DMD gene that is amenable to exon 51 skipping.

Sarepta also has a second exon-skipping therapy, Vyondys 53 (golodirsen), which treats DMD in people with a mutation amenable to exon 53 skipping. The FDA gave the drug accelerated approval in December, almost four months after the agency rejected the drug through a complete response letter.

Both drugs are weight-based with similar prices: about $300,000 per year but up to $1 million annually.

"It's unclear how much a health plan may spend on someone with DMD; however, a recent study from the Muscular Dystrophy Association found that the annual cost for DMD for U.S. society as a whole is around $362-$488 million dollars," says Tegenu. "The price of the newer DMD therapies (Exondys 51 and Vyondys 53) are both estimated to cost approximately $750,000 per year for the treatment of one patient."

Pharma manufacturers continue to focus on the DMD space, and several products, including gene therapies, are in the pipeline.

From RADAR on Specialty Pharmacy