AveXis steps up gene therapy pursuit of Biogen’s SMA pathfinder

New trials expand the program into different SMA populations, and to Europe.

AveXis is expanding trials of its gene therapy for children with spinal muscular atrophy (SMA) with a series of new trials as it plays catch-up with Biogen and Ionis, which claimed the first approval for an SMA drug.

The Chicago biotech already has pivotal trials of its AVXS-101 candidate underway in two variants of the severe neuromuscular disease—types 1 and 2—but says it will now start studies in patients with SMA type 3, older children with type 2, and very young children (less than six weeks old) who have yet to develop symptoms.

It’s also got an eye on the European development of the gene therapy, with a new SMA type 1 study that it hopes will support approval by the EMA.

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Biogen and Ionis’ Spinraza (nusinersen) was approved by the FDA near the end of 2016 and is still the only drug approved to treat SMA, which can affect up to 10,000 children around the world and is one of the leading causes of early death and disability in young children.

The disease causes progressive muscle weakness and paralysis and has four types, with type 1 being the most severe. Biogen has tested its drug on types 1-3, so the expansion of AveXis’ trials program should help it cover the same clinical ground as its rival as well as helping it catch up in Europe, where Spinraza got a green light last July.

AVXS‐101 is based on an adeno‐associated virus vector (AAV9) containing the SMN1 transgene that is designed to deliver a working copy of the gene to cells and cause long-term expression of SMN, a protein which is deficient in SMA. It works in a different way to Spinraza, which is an SMN2 splicing modifier, trying to increase the amount of functional SMN produced by the faulty gene.

“Our focus has always been to serve the SMA community, and our expanded clinical development program is designed to evaluate the impact of AVXS-101 in a broader set of SMA patients,” said Sukumar Nagendran, M.D., AveXis’ chief medical officer.

“We believe the year ahead has the potential to be one of significant clinical progress as we continue toward our ultimate goal of bringing AVXS-101 to the patients and families devastated by SMA.”

With no other approved therapies, Spinraza is gaining ground rapidly in the market and is already on course for blockbuster revenues with sales of $271 million in the third quarter of 2017. Analysts at Leerink have predicted it could bring in $2 billion by 2020, helped by a window of opportunity before other therapies become available.

Aside from AveXis, other companies are also trying to bring SMA drugs through clinical trials, including some Big Pharma heavyweights. Novartis has an SMN2 splicing modifier called branaplam in phase 1/2 testing for SMA type 1, while fellow Swiss group Roche has mid-stage studies ongoing for its neuroprotectant olexisome for types 2 and 3 SMA, as well as SMN2-targeted RG7916—partnered with PTC Therapeutics—in types 1-3.

Meanwhile, Cytokinetics is also active in this area with its fast skeletal muscle troponin activator (FSTA) CK-2127107, which works independently of SMN to boost muscle fiber responses and is in phase 2 testing for SMA types 2, 3 and 4.