FDA approves first oral drug for treatment of spinal muscular atrophy

Reviewed by James Ives, M.Psych. (Editor)Aug 7 2020

The U.S. Food and Drug Administration today approved Evrysdi (risdiplam) to treat patients two months of age and older with spinal muscular atrophy (SMA), a rare and often fatal genetic disease affecting muscle strength and movement. This is the second drug and the first oral drug approved to treat this disease.

Evrysdi is the first drug for this disease that can be taken orally, providing an important treatment option for patients with SMA, following the approval of the first treatment for this devastating disease less than four years ago."

Billy Dunn, M.D., director of the Office of Neuroscience in the FDA's Center for Drug Evaluation and Research

SMA is a hereditary disease that causes weakness and muscle wasting because patients lose lower motor neurons (nerve cells) that control movement. Evrysdi contains a survival of motor neuron 2-directed RNA splicing modifier. The efficacy of Evrysdi for the treatment of patients with infantile-onset and later-onset SMA was evaluated in two clinical studies. The infantile-onset SMA study included 21 patients who had an average age of 6.7 months when the study began. In that open-label study, efficacy was established based on the ability to sit without support for at least five seconds and survival without permanent ventilation. After 12 months of treatment, 41% of patients were able to sit independently for more than five seconds, a meaningful difference from the natural progression of the disease because almost all untreated infants with infantile-onset SMA cannot sit independently. After 23 or more months of treatment, 81% of patients were alive without permanent ventilation, which is a noticeable improvement from typical disease progression without treatment.

Patients with later-onset SMA were evaluated in a second randomized, placebo-controlled study. The study included 180 patients with SMA aged two to 25 years. The primary endpoint was the change from baseline in MFM32 (a test of motor function) total score at the one-year mark. Patients on Evrysdi saw an average 1.36 increase in their score at the one-year mark, compared to a 0.19 decrease in patients on placebo (inactive treatment).

The most common side effects of Evrysdi include fever, diarrhea, rash, ulcers of the mouth area, joint pain (arthralgia) and urinary tract infections. Patients with infantile-onset SMA had similar side effects as individuals with later-onset SMA. Additional side effects for the infantile-onset population include upper respiratory tract infection, pneumonia, constipation and vomiting. Patients should avoid taking Evrysdi together with drugs that are multidrug and toxin extrusion substrates because Evrysdi may increase plasma concentrations of these drugs.

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 drug development for rare diseases. The application was awarded a Rare Pediatric Disease Priority Review Voucher.

The FDA granted this approval of Evrysdi to Genentech, Inc.