The incidence of Clostridium difficile infection has been steadily increasing in recent years. But the antibiotics commonly used to combat it put patients at risk for diarrhea and lead to the emergence of more virulent strains of C. difficile.

Lowy and colleagues developed fully human monoclonal antibodies that target C. difficile, specifically C. difficile toxins A (CDA1) and B (CDB1). Then they conducted a randomized, double-blind, placebo-controlled phase 2 trial to see if these antibodies could reduce the recurrence of C. difficile infection in 200 patients with symptomatic infection who were already receiving metronidazole or oral vancomycin.

A total of 101 patients received the combined CDA1-CDB1 antibody (10 mg of each/kg) in a single intravenous infusion, and 99 patients received a placebo. All patients recorded daily stool counts for 84 days.

A significantly smaller percentage of patients in the treatment group (7%) than in the placebo group (25%) had laboratory-confirmed recurrence of C. difficile infection. In addition, 28% of patients in the treatment group experienced recurrent diarrhea (not necessarily a laboratory-confirmed infection recurrence) compared with 50% in the placebo group.

No significant differences were observed between the groups in terms of diarrhea severity, number of days to resolution, number of patients not responding to treatment, or duration of hospitalization. Adverse events reported were mostly mild to moderate and not significantly different between groups.

Although the study results support the use of antibodies plus antibiotics in reducing the recurrence of C. difficile infection, the authors note that larger studies should be conducted to further support these findings.