By Raghav Mahobe and Bhanvi Satija
(Reuters) -The U.S. Food and Drug Administration said on Tuesday it had approved Biogen Inc (NASDAQ:BIIB)'s drug for treating a form of amyotrophic lateral sclerosis (ALS), making it the first available treatment targeting a genetic cause of the disease.
The drug, branded as Qalsody, got a green light under the agency's accelerated approval pathway.
Biogen will be required to provide more data on the drug's effectiveness for it to remain on the market and for the FDA to grant traditional approval.
Qalsody's approval is based on data that showed it reduced levels of neurofilament protein, an indicator of nerve cell degeneration believed to be tied with progression of the symptoms of the disease.
The effect of the drug is "large enough that you can see that (the) disease is fundamentally different than it would have been if patients weren't on the drug", said Colin Quinn, a neurologist at Penn Medicine ahead of the approval.
Qalsody can be used to treat ALS patients with mutations in a specific gene that leads to accumulation of toxic levels of the superoxide dismutase 1 (SOD1) protein, and is designed to suppress its production.
A panel of FDA experts in March voted in favor of an accelerated approval, but the same panel voted that data from trials of the drug did not support full approval.
To confirm the drug's clinical benefit, Biogen is testing it in another late-stage study in patients who do not yet have symptoms.
Biogen said Qalsody will be priced within a range comparable to other recently launched ALS treatments. The company estimates out-of-pocket expense will be less than $50 per month for a majority of the patients, depending on their insurance plan.
Around 16,000 to 32,000 people have ALS in the U.S., of which 2% cases are associated with SOD1 gene mutations, according to government data.