Results From a Randomized, Placebo-Controlled Clinical Trial of a RBX2660-A Microbiota-Based Drug for the Prevention of Recurrent Clostridium difficile Infection

Clin Infect Dis. 2018 Sep 28;67(8):1198-1204. doi: 10.1093/cid/ciy259.


Background: Despite advancements, recurrent Clostridium difficile infections (CDI) remain an urgent public health threat with insufficient response rates to currently approved antibiotic therapies. Microbiota-based treatments appear effective, but rigorous clinical trials are required to optimize dosing strategies and substantiate long-term safety.

Methods: This randomized, double-blind, placebo-controlled phase 2B trial enrolled adults with 2 or more CDI recurrences to receive: 2 doses of RBX2660, a standardized microbiota-based drug (group A); 2doses of placebo (group B); or 1 dose of RBX2660 followed by 1 dose of placebo (group C). Efficacy was defined as prevention of recurrent CDI for 8 weeks following treatment. Participants who had a recurrence within 8 weeks were eligible to receive up to 2 open-label RBX2660 doses. The primary endpoint was efficacy for group A compared to group B. Secondary endpoints included the efficacy of group C compared to group B, combined efficacy in the blinded and open-label phases, and safety for 24 months.

Results: The efficacy for groups A, B, and C were 61%, 45%, and 67%, respectively. The primary endpoint was not met (P = .152). One RBX2660 dose (group C) was superior to placebo (group B; P = .048), and the overall efficacy (including open-label response) for RBX2660-treated participants was 88.8%. Adverse events did not differ significantly among treatment groups.

Conclusions: One, but not 2, doses of RBX2660 was superior to placebo in this randomized, placebo-controlled trial. These data provide important insights for a larger phase 3 trial and continued clinical development of RBX2660.

Clinical trials registration: NCT02299570.

Publication types

  • Clinical Trial, Phase II
  • Multicenter Study
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Anti-Bacterial Agents / administration & dosage*
  • Biological Therapy*
  • Clostridioides difficile / drug effects*
  • Clostridium Infections / drug therapy
  • Clostridium Infections / prevention & control*
  • Diarrhea / drug therapy
  • Diarrhea / microbiology
  • Diarrhea / prevention & control
  • Double-Blind Method
  • Enterocolitis, Pseudomembranous / prevention & control*
  • Feces / microbiology
  • Female
  • Humans
  • Male
  • Microbiota*
  • Middle Aged
  • Recurrence
  • Treatment Outcome
  • Young Adult


  • Anti-Bacterial Agents

Associated data