Mixed results for Phase III trial of Pfizer's investigational Clostridioides difficile vaccine

In an area where big pharma has failed to find success, US pharma giant Pfizer (NYSE: PFE) has joined the ranks, on Tuesday announcing mixed results from the CLOVER trial (CLOstridium difficile Vaccine Efficacy TRial), a pivotal Phase III study evaluating its Clostridioides difficile (C. difficile) vaccine candidate (PF-06425090) in the prevention of C. difficile infection (CDI).

Initial analyses of two protocol defined secondary endpoints indicated a highly favorable benefit in reducing CDI severity and 100% vaccine efficacy in preventing medically attended CDI, although the trial did not meet its pre-specified primary endpoint of prevention of primary CDI. Safety reviews indicated that the investigational vaccine was safe and well tolerated.

The Pfizer vaccine had been the frontrunner in the C. difficile space following a 2017 decision by French drug major Sanofi (Euronext: SAN) to abandon its trial, which was on track to become the first option available globally for the prevention of C. difficile, and GlobalData analysts estimated at the time said could have reached $400 million in peak sales.