AveXis SMA gene therapy advances toward pivotal trial

Pivotal trial poised to start in the second quarter

AveXis has posted top-line data from a phase 1 trial of its gene therapy against spinal muscular atrophy (SMA). All 15 patients were event-free at 13.6 months of age, a significant improvement over the natural history of the disease.

The phase 1 gave three babies with the genetic muscle weakness disease a low dose of a gene therapy designed to provide them with a functioning SMN gene. A further 12 babies received the larger amount of the gene therapy AveXis sees as the proposed therapeutic dose. By the age of 13.6 months, none of the subjects had suffered an “event”, defined by AveXis as death or the need for medically prescribed respiratory assistance for 16 hours a day for two weeks.

With natural history data suggesting 25% of babies with SMA would experience such an event by 13.6 months of age, the results have encouraged AveXis to push ahead with plans to start a pivotal trial of AVXS-101.

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“We plan to initiate a pivotal trial in the U.S. of AVXS-101 via IV delivery in patients with SMA type 1 in the second quarter of 2017, pending a successful outcome of the CMC type B meeting,” AveXis CEO Sean Nolan said in a conference call with investors to discuss the data.

FDA has pushed back the CMC meeting to May 1, a delay AveXis attributed to the regulator needing more time to review the package submitted by the gene therapy company. But AveXis thinks it will nonetheless be able to get the pivotal trial underway on schedule.

That will move AveXis closer to finding out whether its gene therapy can carve out a niche in a market now being colonized by Biogen and Ionis’ recently approved SMA drug Spinraza. Biogen won approval for the drug on the basis of data linking it to an increase in the number of babies who achieved motor milestones.

AveXis has also generated data on the effect of its gene therapy on motor function. At the last count, seven of the 12 babies in the high-dose cohort could sit unassisted for 10 seconds or more. The September data drop reported eight babies achieved this milestone.