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# Accelerated Approval Mulled for Biogen’s Tofersen
- URL: https://www.fdaweb.com/accelerated-approval-mulled-for-biogens-tofersen/
- Published: 2023-03-20T12:00:00.000Z
- Updated: 2026-09-14T18:20:37.000Z
- Author: David McFarland
- Tags: Drugs, #legacy-id-D5154015

FDA reviewers appear optimistic that Biogen’s amyotrophic lateral sclerosis (ALS) drug tofersen could be considered for accelerated approval despite it failing to show a statistically significant difference from placebo groups for the primary and secondary endpoints in a recent study in patients with the superoxide dismutase 1 (SOD1) gene, which is associated with 20% of familial cases and about 2% of sporadic ALS cases.

Biogen’s submission is proposing neurofilament light chain (NfL) in plasma as a marker of neuroaxonal damage, according to a [briefing document](https://www.fda.gov/media/166326/download?ref=fdaweb.com) released in advance of a 3/22 advisory committee review. “Most recently, scientific literature has established NfL as a biomarker that is significantly elevated in patients with ALS, even more so than in many other neurodegenerative diseases, and NfL levels have been shown to be prognostic for disease progression in ALS,” the FDA document says.

FDA reviewers found the study “markedly underpowered and thus limited in its ability to detect a difference if there was a drug effect; however, there are available data from that study that indicate target engagement of the therapy and a reduction in a biomarker that has been shown to be correlated with disease progression and prognosis in patients with ALS,” according to the briefing document.

On the safety side, reviewers wrote that the primary safety issues related to the potential risk of serious neurologic adverse events that “appear to be associated with the intrathecal route of administration of tofersen (i.e., myelitis, radiculitis, aseptic meningitis, papilledema, and elevated intracranial pressure).” Such reactions in the peripheral and central nervous system have been observed in other antisense oligonucleotide development programs for neurologic diseases with an intrathecal route of administration, the reviewers added.