PTC Therapeutics (PTCT) - Get Report shares have doubled this morning on the surprising (I'd say shocking) news that European regulators recommended the conditional approval of Translarna as a new treatment for patients with Duchenne muscular dystrophy caused by so-called "nonsense" mutations. 

Why is the PTC news a major surprise? Because the same European regulators rejected Translarna in 2013, telling the company the phase II study upon which the regulatory submission was based did not provide convincing proof of efficacy. PTC resubmitted essentially the same package of Translarna data again, and this time, regulators in Europe were satisfied enough to grant the drug conditional approval.

Here's what European regulators said today about their reversal:

Translarna was investigated in a pivotal study involving 174 patients with DMD. The results showed some evidence of efficacy of Translarna in slowing down the loss of walking ability in DMD patients. However, as part of the conditional marketing authorisation, the company will be required to provide comprehensive data on the efficacy of Translarna from an ongoing confirmatory study. Regarding safety, Translarna is generally well tolerated with the most common side effects being headache, nausea and vomiting.

PTC is conducting a large, confirmatory study of Translarna in DMD patients with nonsense mutations, with enrollment expected to complete in the middle of this year. That means there's a rather long wait to find out of Translarna really works because results from the study won't be ready for some time. Meantime, PTC will be able to market the drug to nonsense DMD patients in Europe, or at least try to convince member countries in the EU to settle on pricing and reimbursement. That will be interesting to watch. 

PTC shares are up 128% To $15.32 in Friday's pre-market.

Prosensa (RNA) shares are up 16% to $7.70 in sympathy, and rightfully so. If European drug regulators are going soft on DMD drugs with spotty clinical data, then surely Prosensa's drisapersen has an excellent shot at conditional approval for exon 51 skip DMD patients. 

I sure hope the lawyers at Sarepta Therapeutics (SRPT) - Get Report are busy this morning, because for the same reasons, eteplirsen should be a lock for European approval, if the company can work out the patent issues which have so far blocked the company from seeking approval. 

Adam Feuerstein writes regularly for TheStreet. In keeping with company editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback;

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