What happened

Shares of mid-cap biotech Sarepta Therapeutics (NASDAQ:SRPT) marched almost 11% higher Wednesday morning on elevated volume. The stock's rally was catalyzed by news of encouraging results from an early-stage muscle biopsy study for its experimental Duchenne muscular dystrophy (DMD) therapy, known as golodirsen. Duchenne is a genetic disorder causes muscle wasting; it primarily afflicts young boys, and is the result of a mutation on the X chromosome.

Golodirsen targets patients with deletions of the DMD gene amenable to skipping exon 53. If approved, it would complement the company's first DMD commercial product, Exondys 51. As of 10:30 a.m. EDT Wednesday, Sarepta's shares were up by 10.5%. 

Young man with muscular dystrophy sitting in a wheelchair.

Image Source: Getty Images.

So what

Using the capital from its recent successful commercial launch of Exondys 51, Sarepta is ramping up its efforts to bring additional DMD exon-skipping therapies to market. At present, Exondys 51 only targets about 13% of the total DMD patient population (those amenable to exon 51 skipping) -- underscoring the sizable commercial opportunity offered by the company's diverse pipeline of DMD therapies. In fact, Sarepta is hoping to eventually bring exon-skipping therapies to market that target roughly 80% of all DMD patients

Now what

While golodirsen's initial biopsy results are certainly encouraging (the therapy reportedly led to a significant increase in dystrophin expression), and support the notion that exon-skipping therapies do help to replenish levels of the critical structural protein dystrophin, which is deficient in DMD patients, Sarepta is still a few years away from becoming a multi-product company. Based on its stated development timeline for golodirsen, after all, this particular therapy probably won't be ready for even an accelerated regulatory filing until perhaps 2020.

As far as experimental medicines go, that would actually be a relatively rapid path to the FDA following a positive early-stage readout. But investors may want to curb their enthusiasm somewhat, given that a lot could still go wrong. Sarepta's shares, after all, are already trading at a stately price-to-sales ratio of 51.78 based on Exondys 51's promising start, and on the prospect that a buyer might be lurking in the shadows. 

George Budwell has no position in any of the stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.