Pfizer announced that the phase II study evaluating the company’s Clostridium difficile (C. difficile) vaccine candidate, PF-06425090, provided positive data, based on a pre-planned interim analysis. The randomized study (NCT02561195) examined the safety, tolerability, and immunogenicity of the vaccine in healthy adults 65 to 85 years of age. Pfizer’s vaccine candidate is designed to help prevent C. difficile infection (CDI), which can include life-threatening diarrhea and pseudomembranous colitis, by inducing a functional antibody response capable of neutralizing the two main disease-causing toxins produced by C. difficile (toxins A and B).

“Despite improved infection control measures, C. difficile disease continues to rise, further augmenting an already urgent public health threat with particular negative impact on older adults,” said Kathrin Jansen, Ph.D., senior vice president and head of Vaccine Research and Development for Pfizer. “We are very encouraged by these interim immunogenicity and safety results demonstrating robust increases in vaccine-elicited neutralizing antibodies to both toxins, that we believe could provide protection against C. difficile disease.”

Based on findings from the pre-planned interim analysis, Pfizer’s C. difficile vaccine candidate will progress into phase III in the first half of 2017.

Pfizer’s C. difficile vaccine candidate was granted Fast Track designation by the FDA in August 2014. The FDA’s Fast Track designation is designed to facilitate the development and expedite the review of new drugs and vaccines intended to treat or prevent serious conditions and address an unmet medical need.

The phase II study (NCT02561195) was a randomized, placebo-controlled, observer-blinded study of more than 850 healthy adults 65-85 years of age, evaluating the safety, tolerability and immunogenicity of two dose levels (100µg and 200µg) of Pfizer’s C. difficile vaccine candidate on two different three-dose vaccination schedules (days 1/8/30 and months 0/1/6).