Tofersen NDA Provides Hope for Thousands and Shows Promise of Antisense Technology


When the FDA recently accepted Biogen’s new drug application for tofersen, it signaled hope for thousands of people with SOD1 mutations that cause ALS.

Tofersen works by blocking the production of the SOD1 protein using a molecule called an antisense oligonucleotide. An antisense oligonucleotide is a small string of synthetic DNA that, in this case, is believed to prevent the SOD1 protein from getting made. We were early supporters of antisense research, with investments starting in 2004 and totaling more than $1.5M, and are excited that our investment has led to this and several other significant milestones in ALS.

In October 2021 Biogen announced that the phase 3 VALOR study failed to reach it’s primary endpoint, though there were some signs of reduced disease progression. Then, in June 2022, Biogen released results from a follow-on open label extension study which showed that earlier use of tofersen slowed declines in clinical function, respiratory function, muscle strength and quality of life compared to people who originally were assigned to a placebo but who began taking tofersen several months later during the open label extension study.

The FDA has granted priority review to this new drug application and is expected to decide on whether or not to approve tofersen by January 25, 2023.