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FDA will consider Biogen’s ALS drug, despite mixed results in clinical trial

The Cambridge company’s experimental treatment targets a rare form of the deadly disease.

The FDA has agreed to review Cambridge-based drug maker Biogen’s experimental drug for a rare genetic form of ALS even though the medicine failed to meet its primary goal of slowing functional decline in a late-stage clinical trial.Adam Glanzman/Photographer: Adam Glanzman/Bloo

The Food and Drug Administration has agreed to review Biogen’s experimental drug for a rare genetic form of ALS even though the medicine failed to meet its primary goal of slowing functional decline in a late-stage clinical trial.

The Cambridge-based drug maker said Tuesday that regulators have accepted its application for the drug, called tofersen, and set a deadline of Jan. 25 for making a decision. Biogen is seeking approval under the agency’s accelerated pathway, which is typically reserved for diseases without effective treatments,

The medication is designed to treat a rare form of amyotrophic lateral sclerosis caused by a genetic mutation known as SOD1 that afflicts about 330 people in the US, according to the company. Like other types of ALS, this form ravages the nervous system and gradually robs patients of the ability to speak, eat, and, finally, breathe. The average life expectancy for people with ALS is three to five years from the onset of symptoms.

“If approved, tofersen will be the first treatment to target a genetic cause of ALS, and we hope this will pave the way for further advances in this relentless disease,” said Dr. Priya Singhal, Biogen’s interim head of research and development.


The application could stir controversy. In October, Tofersen did not meet its primary goal of demonstrating statistically significant slowing of decline in functional status of patients. Biogen, however, continued analyzing data and reported in June that early use of the drug slowed progression of ALS in patients with the SOD1 mutation in areas such as respiratory function, strength, and quality of life.

Biogen said it was also seeking approval based on changes the drug produced in a protein called neurofilament in the blood and cerebrospinal fluid. The company described those changes as a biomarker “reasonably likely to predict clinical benefit.”


The application carries echoes of Biogen’s 2021 effort to win approval of Aduhelm, a controversial treatment for an all too common neurological disorder, Alzheimer’s disease. That drug produced contradictory results in two late-stage trials aimed at determining whether it slowed progression of the most common form of dementia. Nonetheless, the FDA approved the medicine ― originally priced at $56,000 a year ― over the strong objections of its independent advisory committee, based on a surrogate biomarker that Biogen said indicated likely benefits to patients.

Troubled by the conflicting views, Medicare officials dealt a death blow to Aduhelm in April. The federal insurer said it will only cover the drug if patients are enrolled in a clinical trial, have mild Alzheimer’s symptoms, and show evidence of a build-up of proteins in the brain known as amyloid plaques, a hallmark of the disease. Following the decision, Biogen announced $1 billion in cuts, stopped marketing Aduhelm, and began looking for a new chief executive.

Brian Skorney, an analyst at the investment bank Baird, said in a note to investors Tuesday that given the FDA’s approval of Aduhelm based on a surrogate biomarker, he sees a “reasonable likelihood” that regulators will clear tofersen as well. He predicted that Biogen would price the drug at hundreds of thousands of dollars ― “definitely mid-six figures,” he said in an interview.

But he said the drug probably wouldn’t have much of an impact on Biogen’s business. The form of ALS it treats affects a small number of patients, the results of clinical trials were ambiguous, and the drug requires monthly injections into patients’ spinal canal, which, he said, is “a lot to ask for patients and caregivers to accept without any demonstrable clinical effect.”


Jonathan Saltzman can be reached at