2822 Twelve-Month Durability of Microbiota-Based Drug RBX2660 for Preventing Clostridioides difficile Infection (CDI) Is Not Associated With Patient Demographics: Sub-Population Analysis of a Phase 2 Open-Label Study

INTRODUCTION: Recurrent Clostridioides difficile infection (rCDI) is an urgent public health threat that is associated with significant mortality and substantial medical cost. Microbiota therapy is gaining acceptance to prevent rCDI in multi-recurrent individuals. Two Phase 2 clinical studies have reported the efficacy of RBX2660, a standardized, stabilized microbiota-based drug, in preventing rCDI. To address the suggestion of demographic differences on treatment outcome, we investigated two key demographic stratifications (age and gender) of rCDI subjects enrolled in the Phase 2 open-label study and their associations with outcomes through 12 months post-RBX2660 treatment. METHODS: Data were drawn from a multi-center, open-label Phase 2 study (NCT02589847) in which subjects with multi-recurrent CDI received <2 doses of RBX2660 delivered via enema 7 days apart; this analysis includes data to 12 months after completion of dosing, with ongoing follow-up through 24 months. Efficacy was defined as absence of CDI recurrence through 56 days after the last dose; and durability is defined as a continued lack of reported CDI occurrence. Subjects were censored from subsequent time intervals if they experienced a new CDI occurrence. Fisher’s exact test was performed comparing the proportion of treatment subjects who were recurrence-free by subgroup: age, >65 years vs. <65 years; sex, male vs. female. RESULTS: This study included 149 RBX2660-treated participants in the USA and Canada. Eight-week efficacy for RBX2660 in preventing rCDI (76.5%; 114/149) was higher than CDI-free rates in the historical control group (51.8%, 57/110; P < 0.0001). Of the 114 RBX2660 subjects who achieved treatment success through 8-weeks, 109 subjects had 6-month follow-up data. Of those, three experienced a new CDI episode through 6 months. Between 6 and 12 months, two additional subjects experienced a CDI occurrence. The overall durability through 12 months is 91.7%, as four of the 109 subjects didn’t complete 12-month follow-up and were conservatively assessed as failures. Age and gender did not have a statistically significant impact on efficacy outcome (Table 1). The safety profile through 12 months is consistent with previous reports for RBX2660. CONCLUSION: RBX2660, a microbiota-based drug, was efficacious for preventing rCDI, with clinical durability to at least 12-months after treatment. Importantly, durability was not dependent on age or gender. Twenty-four month follow-up of efficacy and safety are ongoing.

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