The US Food and Drug Administration has cleared Merck's Clostridium difficile (CDI) recurrence jab Zinplava after having extended the review period by three month.

Zinplava (bezlotoxumab) is indicated to reduce recurrence of CDI in patients 18 years of age or older who are already receiving antibacterial drug treatment and are at high risk for recurrence.

The firm stressed that its drug is not an antibacterial and is not indicated to actually treat the infection, but is a monoclonal antibody designed to neutralise C. difficile toxin B, which can damage the gut wall and cause inflammation, leading to diarrhoea.

Around one-in-four patients experience a recurrence after the initial episode, and more than 40 percent of these have further recurrence, highlighting the need for new options able to break the infection cycle.

Pivotal Phase III clinical studies showed the rate of infection recurrence through week 12 to be significantly lower in patients given Zinplava (17.4 percent and 15.7 percent) or Zinplava and actoxumab (15.9 percent and 14.9 percent) than those taking a placebo (27.6 percent) and (25.7 percent), respectively.

According to the US Centers for Disease Control and Prevention, C. difficile is estimated to have caused almost half a million infections in the US alone in 2011, with 29,000 deaths, often within 30 days of initial diagnosis.

Merck said it anticipates launching Zinplava in first quarter of next year.