1950. Prevention of Recurrent Clostridium difficile at Six Months Following Treatment With Microbiota-Based Therapy RBX2660: Durability Results From a Phase 2 Open-Label Study

BACKGROUND: Numerous microbiota-based therapies are being evaluated for prevention of C. difficile infection (rCDI), a public health threat with high recurrence rates associated with the current standard of care. RBX2660, a standardized microbiota-based drug, was efficacious for preventing rCDI in a double-blinded Phase 2b clinical study (PUNCH CD 2). Herein we report the durability of RBX2660 beyond the initial primary clinical end-point of a subsequent Phase 2 open-label study, demonstrating rCDI prevention at 6 months post-treatment. METHODS: This prospective, multi-center, open-label Phase 2 study enrolled subjects who had experienced either ≥2 recurrences of CDI following standard-of-care antibiotic therapy or ≥2 episodes of severe CDI requiring hospitalization. Participants received up to two doses of RBX2660 delivered via enema with doses 7 days apart. The primary endpoint of the open-label clinical study defined efficacy as absence of CDI at 8 weeks from the last dose. Safety follow-ups and durability assessments occurred via telephone at 3, 6, 12, and 24 months. The study is ongoing, and not all subjects have completed their assessments. RESULTS: This study included 149 RBX2660-treated subjects and 110 historical control subjects from 31 and 4 centers, respectively, in the United States and Canada. At 8-weeks post-treatment, RBX2660’s efficacy in preventing rCDI (79.9%; 119/149) was higher than CDI-free rates in the historical control group (51.8%, 57/110; P < 0.001). Of the 119 subjects who were determined to be treatment success at 8 weeks, 117 have data through 6 months, of which 8 were exited for non-CDI reasons. Of those 109 subjects through the 6-month follow-up, 3 (2.8%) had a new CDI beyond 8 weeks after enema. The 6-month long-term CDI-free rate was 97.2% (106/109) (median follow-up: 182 days; mean: 177 days). CONCLUSION: RBX2660, a microbiota-based drug, was efficacious for the prevention of recurrent CDI with long-term durability at 6-months post-treatment; a result consistent with 6-month rCDI prevention reported for the Phase 2b PUNCH CD 2 trial. Long-term follow-up of RBX2660 safety and efficacy 24 months is ongoing. This analysis was funded by Rebiotix Inc., Roseville, MN. DISCLOSURES: S. Mische, Rebiotix, Inc.: Employee, Salary. R. Orenstein, Rebiotix, Inc.: Scientific Advisor, Consulting fee. E. R. Dubberke, Rebiotix, Inc.: Scientific Advisor, Consulting fee. S. Khanna, Rebiotix, Inc.: Scientific Advisor, Consulting fee and Research support. G. Hecht, Rebiotix, Inc.: Scientific Advisor, Consulting fee. H. Dupont, Rebiotix, Inc.: Investigator, Research support. C. Lee, Rebiotix, Inc.: Scientific Advisor, Consulting fee. K. Blount, Rebiotix, Inc.: Employee, Salary.