- Biogen's hopes for its experimental spinal muscular atrophy (SMA) treatment were substantially bolstered on Monday by new Phase 3 data showing a statistically significant improvement in motor function among patients with a later-onset type of the muscle-weakening condition.
- Patients receiving the drug, known as nusinersen, saw an average improvement of 4 points in a scale used to measure motor function, while those on placebo declined by an average of 1.9 points.
- Biogen, which depends heavily on revenue from its portfolio of drugs for multiple sclerosis, hopes to launch nusinersen in the U.S. as early as the end of this year or the first quarter of next year. Another Phase 3 study testing nusinersen in infantile-onset SMA read out positive in August.
Biogen has already submitted applications for approval of nusinersen to the Food and Drug Administration and the European Medicines Agency, based on the trial results in infantile-onset SMA.
Now, with more positive data in hand, Biogen is stopping its Phase 3 study in later-onset SMA early and gearing up for a U.S. launch. All 126 patients currently enrolled in the "CHERISH" will be allowed to move into an open-label transition study to continue receiving the drug.
Patients with SMA suffer from progressive muscular atrophy and weakness resulting from the loss of motor neurons in the spinal cord and lower brain stem. Severe forms of the condition, which correspond to the amount of survival motor neuron (SMN) proteins lost, can result in paralysis and difficulty breathing and swallowing.
Infantile-onset SMA is considered the more severe form of the disease, although the later-onset types 2 and 3 are still life-altering. There are no currently approved treatments for SMA in the U.S.
The 5.9 point difference in motor scale scores seen between the treatment and placebo arms of the CHERISH study exceeds what is typically considered clinically meaningful, Biogen said.
Monday's results further validate Biogen's decision in August to exercise its option to license nusinersen from Ionis Pharmaceuticals, for which it paid Ionis $75 million upfront.
Biogen is heavily reliant on sales of its MS drugs Tecfidera and Tysabri and recently narrowed its focus further by spinning off its hemophilia business. An approval for nusinersen would give Biogen a new source of growth within its neurological portfolio and help it corner the SMA market.
Jefferies, an investment firm, estimates 2025 revenues at $1.5 billion, based on a 40% market penetration among type 1 patients (infantile-onset) and a 38% penetration among patients with types 2 and 3.
Biogen is furthest along in SMA development. Yet other competitors could be nipping at its heels — AveXis recently won FDA support for design of a Phase 1 study evaluating its SMA gene-therapy.