Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of PTC Therapeutics (NASDAQ:PTCT), a biopharmaceutical company focused on developing small-molecule drugs to treat genetic mutations, vaulted higher by as much as 88% after receiving a positive opinion from the Committee for Medicinal Products for Human Use (CHMP) in Europe for translarna, which is the branded name given to ataluren, the company's lead investigational compound.

So what: According to PTC Therapeutics' press release, following its request for a reexamination of translarna as a treatment for nonsense mutation Duchenne muscular dystrophy (nmDMD), the CHMP (essentially the equivalent of the FDA panel in the U.S.) recommended the conditional marketing authorization of the compound. This positive CHMP decision will be taken into consideration by the European Medicines Agency on whether to grant EU market approval over the coming months. Usually this is about a three-month process, although similar to how investigational drugs are reviewed in the U.S., the EMA is not obligated to follow the advice of the CHMP. If approved, translarna would mark the first FDA-approved therapy specifically for nmDMD. Following this decision Credit Suisse boosted its price target on PTC to $40 from $35, while rival Prosensa (NASDAQ:RNA) rocketed higher by as much as 35% in anticipation that its DMD-based exon-skipping therapy will be viewed favorably in the EU as well.

Now what: The results from PTC's phase 2b trial were remarkably solid, with a 31.3 meter benefit noted in the six-minute-walk-distance (6MWD) relative to the placebo after 48 weeks. Further, in a pre-specified group of patients unable to walk 350 meters, the 40 mg dose of translarna improved their 6MWD by 68 meters relative to the placebo. Based on today's opinion and these results I'm certainly leaning toward the therapy being approved throughout Europe, although investors should keep in mind that the company is also running a broader phase 3 trial at the moment, and we have seen DMD drugs succeed in phase 2 studies only to fall flat on their face in phase 3. While this is an exciting day for nmDMD sufferers overseas who could soon be looking at better quality of life, investors would probably be wise to wait for a pullback before even considering buying into PTC.

PTC shares may have skyrocketed today, but even it could struggle to keep pace with this top stock over the long run
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Sean Williams has no material interest in any companies mentioned in this article. You can follow him on CAPS under the screen name TMFUltraLong, track every pick he makes under the screen name TrackUltraLong, and check him out on Twitter, where he goes by the handle @TMFUltraLong.

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