Clostridium Difficile Vaccine Successful in Phase 2 Clinical Trial

Pfizer recently announced positive results from a phase 2 study of a candidate vaccine to prevent a Clostridium difficile infection.

Approximately 29,000 deaths per year are caused by C. difficile in the United States alone. There is currently no vaccine against the bacteria, which can cause life-threatening diarrhea and pseudomembranous colitis, according to a press release from Pfizer.

C. difficile infections are typically seen in patients with altered gut microbial flora, which is typically the result of antibiotics. Since elderly patients tend to be on multiple medications, their treatment regimen combined with a weakened immune system can lead to a serious infection with the bacteria.

C. difficile infection was classified as an urgent public health threat by the US Centers for Disease Control and Prevention in 2013, according to Pfizer.

Included in the study were 850 patients aged 65 to 85. The randomized trial was designed to determine the safety, tolerability, and immunogenicity of PF-06425090 in 2 different doses on 2 different 3-dose vaccination schedules.

An interim analysis of the trial revealed that the candidate vaccine successfully prevented C. difficile infection in this vulnerable population.

Based on these positive top-line results, Pfizer plans to move the candidate vaccine into phase 3 clinical trials during the first half of the year, according to the press release. PF-06425090 was previously granted FDA fast track designation in August 2014 due to the current unmet need of prevention options for C. difficile.

Current treatment options may offer improvements, but do not provide long-term protection, with up to 25% of patients facing 1 recurrence, and up to 65% experiencing multiple recurrences, according to Pfizer.

If successful in further clinical trials, patients with this life-threatening infection may have a long-term treatment option.

“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, PhD, senior vice president and head of Vaccine Research and Development for Pfizer, Inc. “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.”