What: Shares of Spark Therapeutics (NASDAQ:ONCE), a leader in the field of gene therapy, ripped higher today by more than 50% at one point on tremendous volume. The fuel driving this rocket-like surge was the announcement that the company's lead experimental gene therapy product candidate, SPK-RPE65, met its primary endpoint of improving functional vision in an intervention group, relative to a control group, of patients with RPE65-mediated inherited retinal dystrophies. The company said SPK-RPE65 was also generally well-tolerated, with no serious adverse effects occurring in the experimental group as a result of treatment.  

Source: Wikimedia Commons

So what: On the scientific side of the ledger, gene therapy as a viable treatment modality is finally starting to make headway, at least for some diseases. And Spark's ability to successfully reverse some of the impacts of RPE65-mediated inherited retinal dystrophies with its experimental-stage product is certainly another important achievement for gene therapy as a whole. 

From an investment standpoint, the Street thinks SPK-RPE65 could eventually achieve peak sales of around $600 million, meaning that Spark's shares are presently trading at less than 3 times this estimate, even after today's huge move upwards.

Now what: Given the strength of these late-stage results, Spark's management plans on filing for the therapy's regulatory approval with the U.S. Food and Drug Administration in 2016. Before then, though, I would expect the company to take advantage of this spike in share price to raise funds via a secondary offering, which is almost standard procedure among clinical-stage biotechs following a positive clinical catalyst. Investors that missed this positive clinical catalyst therefore may have a chance to buy shares at a lower price in the days ahead. Stay tuned.