The Food and Drug Administration on Tuesday authorized the first drug for a rare genetic form of the neurological disorder A.L.S., despite uncertainty about the treatment’s effectiveness.
The decision reflects the agency’s push toward greater flexibility in approving treatments for patients with devastating illnesses and few, if any, options.
Biogen, the pharmaceutical company bringing the drug to market, said it would price the drug “within a range comparable to other recently launched A.L.S. treatments.” An A.L.S. therapy approved last year was priced at $158,000 annually.
The drug, which is known scientifically as tofersen and will be sold under the brand name Qalsody, targets a mutation in a gene known as SOD1 that is present in about 2 percent of the roughly 6,000 cases of A.L.S. diagnosed in the United States each year. Fewer than 500 people in the United States at any given time are expected to be eligible.
The agency authorized the treatment via a policy that allows a drug to be fast-tracked onto the market under certain circumstances before there is conclusive proof that it works. Biogen will be required to provide confirmatory evidence, from ongoing clinical research, to keep the drug on the market.
The decision is the first conditional approval granted for a medication for A.L.S., or amyotrophic lateral sclerosis, which generally causes paralysis and death within a few years. Fewer than half the patients eligible for Qalsody survive more than three years after their diagnosis.
The approval is based on evidence that the drug can significantly reduce levels of a protein that has been linked to damage to nerve cells. Biogen has argued that these results are reasonably likely to help patients, even though the drug, in a clinical trial, did not significantly slow the progression of the disease, as measured by patients’ ability to speak, swallow and perform other activities of daily living.
Despite the uncertainty about its benefit, Qalsody’s approval is widely seen as more justifiable than that of Aduhelm, another drug from Biogen. Aduhelm prompted an outcry when the F.D.A. approved it in 2021 to treat Alzheimer’s despite a lack of evidence that it worked.
At a meeting last month, a panel of independent advisers to the F.D.A. unanimously recommended that the agency grant conditional approval of Qalsody, even though a majority of advisers concluded that there was not convincing evidence that it was effective.
A.L.S. patients and advocacy groups mounted an impassioned campaign for the drug. F.D.A. officials wrote last month that their approach to evaluating such medications had been shaped by the agency’s “interactions with patients and their caregivers who describe their willingness to accept less certainty about effectiveness in return for earlier access to much-needed medicines.”
Patients receive Qalsody as an injection into the spinal canal every few weeks. The drug was found to be generally safe, though a small number of patients developed inflammation of the spinal cord.
Before Qalsody, only three A.L.S. medications were approved in the United States, and they have not significantly altered the course of the disease.