Biogen's ALS ambitions on pause as FDA delays approval decision by 3 months

The long and winding road Biogen’s tofersen has taken to FDA approval just got longer, with the agency delaying its decision on the amyotrophic lateral sclerosis (ALS) drug until April.

Biogen’s tofersen plans were almost derailed a year ago by a phase 3 study that revealed the antisense medicine failed to improve the functional status of SOD1-ALS patients compared to placebo after six months, causing the 108-subject study to miss its primary endpoint.

Undeterred, the Big Pharma used 12-month data from the phase 3 VALOR trial and an open-label extension to show that an earlier initiation of tofersen treatment slowed decline across measures of clinical and respiratory function, strength and quality of life.

The FDA seemed convinced enough to consider the approval application and penciled in a decision date of Jan. 25, 2023.

Now, the agency has pushed the date back to April 25, Biogen said in a release Monday morning. The FDA’s reasoning is that it considers responses submitted by Biogen as part of the ongoing review to be a “major amendment” to the application, requiring additional time to consider.

The FDA first accepted the tofersen approval application back in July under the accelerated pathway and granted priority review. If approved, the Ionis Pharmaceuticals-partnered prospect would be the first drug to treat a genetic cause of ALS.

While the FDA reviews the drug, Biogen said it will continue its early access program for participants spanning over a dozen countries. An open-label extension and the phase 3 ATLAS study in pre-symptomatic individuals with motor neurone disease and the SOD1 genetic mutation remain ongoing.

Other potential ALS therapies have also had a tricky time with the regulator. In June, the FDA notified Amylyx Pharmaceuticals that it was extending its decision date for its drug AMX0035 to review additional data analyses. The therapy was previously voted down by an agency advisory committee in March in a tough vote that followed riveting patient testimony.

Clinical trials have been even less forgiving, with Clene Nanomedicine seeing its shares slump after its ALS drug CNM-Au8 came up short in a phase 2 trial in October. A month earlier, Biohaven announced its ALS drug verdiperstat failed to improve disease progression.