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What: Shares of Optimer Pharmaceuticals (Nasdaq: OPTR) surged today by as much as 11.5% on news that the company's DIFICID drug performed well in phase 3 study results.

So what: The drug is meant to treat clostridium difficile-associated diarrhea, or CDAD. Patients being treated with the drug showed speedier resolution of diarrhea and lower risk of death during the first 12 days after treatment compared to patients treated with Vancomycin.

Now what: The primary author of the analysis, Dr. Sarah Walker, said, "We were encouraged by the results of the phase 3 clinical studies and believed that a more comprehensive look at the patient characteristics of the phase 3 study participants might yield even greater insights into the use of DIFICID for the treatment of CDAD." Canaccord Genuity, which rates the stock a "Buy," followed up with some positive comments that additional upside may come from increased uptake among doctors. The company has a $20 price target on Optimer shares, which would represent a 38% to today's close.

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