U.S. Food and Drug Administration staff on Monday said Biogen's investigational ALS drug may have a "clinical benefit" on a rare and aggressive form of the disease, despite failing a broader late-stage clinical trial last year.
A separate exploratory analysis of the drug suggests "a clinical benefit with a longer duration of treatment," the staff wrote.
It also found that tofersen reduced levels of a protein called neurofilament light (NfL,) which is "correlated with disease severity, disease progression rate, and survival in patients with ALS," according to the FDA staff.
The first is to move forward with recommending accelerated approval based on tofersen's reduction of NfL in ALS patients.
"SOD1-linked ALS is a particularly rare and aggressive form of an already rare and devastating disease," said Dr. Neil Thakur, The ALS Association's chief mission officer.