Shares of Optimer Pharmaceuticals (OPTR) rose nearly 7% on Tuesday after the drug maker said its antibacterial diarrhea treatment Dificid was approved by the Food and Drug Administration.

Dificid was granted marketing approval as a treatment of Clostridium difficile-associated diarrhea, or CDAD, in adults 18 years and older. The company said it plans to start selling the drug in the U.S. in this year’s third quarter.

In the largest ever late-stage clinical trial of CDAD, Dificid had response rates that were better than oral vancomycin in sustaining clinical response through 25 days beyond the end of treatment. The drug is now the only FDA-approved antibacterial treatment proven to be superior to vancomycin.

“The clinical development program for Dificid was designed to address one of the greatest challenges in managing CDAD, disease recurrence,” Optimer CEO Pedro Lichtinger said in a statement, noting the company is proud to provide patients with an “effective treatment” proven to do just that.

CDAD is associated with a bacterial infection in the lining of the gut that can cause severe diarrhea, inflammation of the colon and in some cases death. The infection is expected to affect more than 700,000 people in the U.S. each year, though the incidence may be higher as many cases go undiagnosed, according to Optimer.

The disease is especially noted for the high number of patients, roughly 20% to 30%, who experience disease recurrence, or the reappearance of symptoms following initial antibiotic treatment.

As part of the approval, the company has committed to conducting a microbiological surveillance program to identify the potential for decrease susceptibility of CDAD, as well as two post-marketing studies in pediatric patients.

Optimer also plans on conducting a randomized trial to evaluate the efficacy of Dificid in the treatment of patients with multiple CDAD recurrences.

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