WASHINGTON (NEWSnet/AP) — Food and Drug Administration regulators on Tuesday approved a new treatment for a rare form of Lou Gehrig’s disease, though they are requiring further research.

Biogen’s new injectable drug, tofersen, is meant for for patients with a rare genetic mutation of ALS that's estimated to affect less than 500 people in the U.S. ALS, or amyotrophic lateral sclerosis, is a fatal disease that destroys nerve cells needed for basic functions like walking, talking and swallowing.

Approval came via FDA’s accelerated pathway, which allows drugs to launch before they are confirmed to benefit patients. While accelerated approval has long been an option for treatments of serious conditions, the shortcut has come under increasing scrutiny.

The FDA is requiring Biogen to continue studying the drug in a trial of people who carry the genetic mutation but do not yet have symptoms.

Patients receive three spinal injections of the drug over a two-week period, followed by a monthly dose. The most common side effects linked to the drug were pain, fatigue and increased spinal fluid.

Biogen did not announce a price for its drug Tuesday but said it will be “comparable to other recently launched ALS treatments."

The ALS Association and other patient groups hailed the approval.

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