C. difficile Vaccine Candidate Soon to Start Phase 3 Trial

Strategic Alliance Partnership | <b>C Diff Foundation</b>

Phase 2 study shows promising results for potential C. difficile vaccine candidate.

Global pharmaceutical enterprise Pfizer today announced positive results from its phase 2 study of vaccine candidate PF-06425090 designed to help prevent Clostridium difficile (C. difficile) infection in adults.

The randomized phase 2 study examined the immunogenicity, safety, and tolerability of the vaccine in 854 healthy adults 65 to 85 years old. Researchers found the experimental vaccine could potentially inhibit severe diarrhea and pseudomembranous colitis by inducing a functional antibody response that can neutralize the two main disease-causing toxins (toxin A or B) produced by C. difficile.

The study observed two dose levels (100 µg and 200 µg) of the vaccine candidate. Each study participant randomly received three doses of vaccine on one of two vaccine schedules (days 1/8/30 and months 0/1/6).

The primary outcome measures of the study included:

• Proportions of individuals in each vaccine group with toxin A- specific neutralizing antibody level greater than or equal to the specified threshold for toxin A. (Time Frame: 7 days or 1 month after dose 3)

• Proportions of individuals in each vaccine group with toxin B- specific neutralizing antibody level greater than or equal to the specified threshold for toxin B. (Time Frame: 7 days or 1 month after dose 3)

C. difficile infections have made several headlines during the last few years as an emerging threat against public health, particularly among the older demographic. “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 protections against C. difficile disease,” said Kathrin Jansen, PhD, senior vice president and head of Vaccine Research and Development for Pfizer Inc. in a news release.

Officials have confirmed that based on findings from the pre-planned interim analysis, the PF-06425090 candidate will transition into phase 3 come the first half of 2017.