Drug Development

UPDATED: Spark adds fresh evidence that pioneering gene therapy could be a game changer for patients

Spark Therapeutics has added another impressive round of late-stage data demonstrating that its gene therapy for an inherited eye disease could be a game changer for patients. This latest readout included positive outcomes for 9 crossover patients who received voretigene neparvovec (SPK-RPE65) a year ago, along with promising longer term results on the original group of 20 patients.

Nine patients with inherited retinal disease caused by mutations in the RPE65 gene were put in the control arm of the study, and all volunteered for the gene therapy after investigators concluded that the original treatment group had benefited markedly with significant gains in vision. A year after treatment, Spark says that 8 of the 9 “demonstrated the maximum improvement measurable on the primary endpoint at one year.” And the first 20 patients who were treated with their gene therapy have demonstrated a sustained benefit in vision, speaking to the durability of the change.

But it wasn’t all upbeat for Spark today. Analysts noted that the biotech expects a significant delay in its regulatory filing, citing CMC issues.

“ONCE also reported that the BLA submission will be delayed until early 2017 due to incomplete CMC data,” noted Wedbush analyst David Nierengarten. “(W)e have pushed back the expected launch from 4/1/17 to 10/1/17 in the US, which reduces our PT by $1.” Investors didn’t overlook the unexpected setback, sending Spark’s shares down slightly.

Voretigene neparvovec is a leading gene therapy in a diverse field that has produced remarkably mixed results. Widely billed as the first gene therapy likely to go to the FDA in search of marketing approval, it’s become a test case for discussions on pricing a potential one-time treatment. And it’s also helped underscore the simple fact that not all gene therapies are equal, as developers test new and better delivery vehicles and corrective genes.

Spark wants to be the leader, and it’s been making its case with data like this.

Looking for evidence of a functional improvement in vision, Spark reported that the 8 additional patients hit the top rung in the tracked change in bilateral mobility testing. On light sensitivity testing, the eight also improved, “with an average improvement of nearly 200-fold, compared to the more than 100-fold improvement average seen in the 301 study subjects. Subjects in the (crossover) study demonstrated an average visual acuity improvement of 4.5 letters, averaged across both eyes, compared to an average improvement of eight letters by the same analysis in the (original) 301 study.”

Spark also added some fresh evidence that its pioneering treatment could live up to its stock symbol {$ONCE), with evidence that the treatment was equally effective two years after treatment as one. According to Spark:

The mean durability of benefit was sustained at 1.9 lux levels after two years, compared with the improvement of 1.9 lux levels after one year. The more than 100-fold improvement average seen in the original intervention group at one year similarly was maintained through at least two years.

Spark—a spinout of Children’s Hospital of Philadelphia—has a market cap of $1.8 billion.

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