The Food and Drug Administration approved Tofersen, an investigational drug developed by Biogen and Ionis Pharmaceuticals, to treat a rare genetic form of amyotrophic lateral sclerosis (ALS) Tuesday afternoon.

The FDA approved Tofersen to treat SOD1-mutation-mediated ALS based on a reduction in plasma neurofilament light, a blood-based biomarker of nerve injury and neurodegeneration. SOD1-mutation-mediated ALS affects approximately 330 people in the U.S. and is considered “uniformly fatal” by the National Institutes of Health.

The drug is administered via spinal injection with a recommended dosage of 100 mg. Patients receive three initial doses administered at 14-day intervals followed by a maintenance dose every 28 days. 

The FDA’s decision came just over a month after an advisory committee issued a mixed vote on Tofersen.

In a press statement released after the approval was announced, Biogen celebrated the FDA’s decision and reflected on the company’s “steadfast” commitment to pursuing treatments for the neurodegenerative disease.

“Today also marks a pivotal moment in ALS research as we gained, for the first time, consensus that neurofilament can be used as a surrogate marker reasonably likely to predict clinical benefit in SOD1-ALS,” Biogen CEO Christopher A. Viehbacher said in a statement. “We believe this important scientific advancement will further accelerate innovative drug development for ALS.”

The approval was also handed down the same day Biogen released its Q1 earnings report.

“Today’s approval of QALSODY represents a scientific advancement for the ALS community. We thank the people with SOD1-ALS whose participation in the clinical studies made this day possible,” said Ionis CEO Brett Monia, PhD, in a statement. We are proud of the Ionis scientists whose dedication made the discovery of this medicine possible, and we are appreciative of our partners at Biogen for their ongoing commitment to ALS.”

Tofersen’s success has prompted hope that other treatments for ALS and specifically SOD1 mutations, could gain momentum going forward. Last year, medical communications legend Lisa Stockman-Mauriello passed away after battling SOD1. She was a longtime advocate for expanded use of Tofersen and future clinical trials to include a parallel-expanded access program.

The regulatory greenlight also sparked widespread praise from the ALS community, which had been eyeing approval of the drug for months. 

The ALS Association heralded another victory for the patient community, with Tofersen marking the second approved treatment for ALS in less than a year and the third since 2017.

“The FDA’s decision marks a significant step in our effort to make ALS livable for everyone, everywhere, until we can cure it,” said Calaneet Balas, CEO of The ALS Association, in a statement. “This is the second time in less than a year our community gets to celebrate the approval of a new drug to treat ALS and we have great hope for the future of antisense technology.”  

Additionally, the ALS Therapy Development Institute said the decision “inspires hope” for people living with SOD1-mutation-mediated ALS.

“This approval is a culmination of decades of research on genetic drivers, preclinical development, biomarker identification, & people with ALS participating in clinical trials,” the organization tweeted.

Paul Wicks, PhD, a neuropsychologist and independent consultant investigating ALS, said he had spent 20 years hunting down SOD1-mutation-mediated ALS and added “it is a good day.”

This story has been updated to include commentary from Ionis Pharmaceuticals.