USA — The US Food and Drug Administration (US FDA) has extended the review period for Biogen and Ionis’ amyotrophic lateral sclerosis (ALS) therapy Tofersen by three months.

The approval decision was originally expected to be by 25 January 2022, but this has now been extended to 25 April 2023.

Without going into specifics, Biogen confirmed the extended deadline today, stating that it had submitted responses to FDA queries that amounted to a major amendment to the filing, necessitating additional review time.

Tofersen was one of Biogen’s most important near-term launch prospects just a few weeks ago, so the delay would have been significant.

However, it has since announced promising results with Eisai-partnered Alzheimer’s disease candidate lecanemab, which, if confirmed, could put the biotech back on track following the failure of its previous Alzheimer’s therapy, Aduhelm (aducanumab).

The FDA began reviewing tofersen in July under its accelerated approval pathway and a priority review based on the findings of the VALOR trial, which disappointed at its first readout last year but has since seen improved data indicating that it can slow the progression of the devastating neurodegenerative disease.

Tofersen is an antisense oligonucleotide that targets a rare form of ALS caused by mutations in the superoxide dismutase 1 gene (SOD1).

Mutations in the SOD-1 gene are linked to about 2% of cases of ALS, also known as motor neuron disease (MND). In the United States, approximately 31,000 people have ALS.

Priya Singhal, Biogen’s global head of global safety and regulatory sciences, stated that the company is “committed to providing any details the agency requires to complete the review of tofersen,” adding that Biogen will continue to provide the drug to patients through its early-access program in the meantime.

Biogen has not provided an update on whether the FDA will require an advisory committee meeting to review the drug’s data. There is currently no set date for this.

It remains to be seen whether the VALOR data will persuade the FDA to grant conditional approval while it awaits the results of a confirmatory phase 3 trial (ATLAS) in SOD1-ALS, which is expected to produce results in 2026.

Biogen is currently squeezed between competitive pressures on its multiple sclerosis and spinal muscular atrophy products and virtually zero sales of Aduhelm.

Therefore, a lot is riding on its near-term pipeline, which includes lecanemab, tofersen, the antidepressant zuranolone developed in collaboration with Sage Therapeutics, and lupus therapies litifilimab and dapirolizumab pegol.

Despite reservations about its efficacy, the FDA approved Amylyx’s Relyvrio (sodium phenylbutyrate and taurursodiol) last month, ending a five-year drought in new ALS therapies.

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