Investigating RBX2660 for Recurrent C Difficile Infection

Clostridioides difficile (C diff) infection is the most common healthcare-associated infection in the US, accounting for significant patient mortalities and hospital burdens. Recurrent C diff infection (rCDI) is associated with even higher patient deaths, and is recognized as an urgent public health threat.

RBX2660 is a standardized, stabilized, investigational microbiota-based live biotherapeutic for the treatment of C diff. The therapy has been evaluated in 5 prospective clinical trials. One study, presented at last week’s Making a Difference in Infectious Diseases (MAD-ID) 2022 Annual Meeting, examined the safety and efficacy of RBX2660 as administered under US Food and Drug Administration (FDA) enforcement discretion.

This retrospective analysis utilized data collected from electronic health records of adult rCDI patients. The primary safety set included patients who had no treatment history with RBX2660, and who had continuous treatment follow-up for 6 months after receiving the therapy. Study outcomes of interest included safety, absence of rCDI within 8 weeks after RBX2660, and clinical response duration.

The study included a total of 94 patients, enrolled from 5 sites between November 2015-September 2019. The most common comorbidities included gastroesophageal reflux disease (47.9%), irritable bowel syndrome (17%), gastritis (11.7%), constipation (8.5%), microscopic colitis (7.4%), diverticulitis (6.4%), Crohn’s disease (5.3%), and ulcerative colitis (4.3%). Additionally, 16% of patients were using concomitant immunosuppressants, including glucocorticoids (7%) and monoclonal antibodies (6%).

Of the 94 participants, 64 were in the primary safety set and were treated with RBX2660. The treatment success rate was 82.8% (n = 53), and there was no significant difference between the patients who received 1 dose of RBX2660 (83.3%; n = 20) and the patients who received 2 doses (82.5%; n = 33).

Among those who initially responded to treatment, 88.7% (n = 47) had a sustained clinical response after 6 months. The safety outcomes were comparable to other RBX2660 studies, with 92.2% of adverse events qualified as mild-to-moderate severity. This safety profile extended to the participants with autoimmune disorders and other inflammatory conditions.

The investigators concluded that RBX2660, administered under FDA enforcement discretion, demonstrated high clinical efficacy in reducing rCDI for 6 months. These results were corroborated by other studies, and by real-world observances of the safety and efficacy of RBX2660 in patients with common rCDI comorbidities.

This study, “RBX2660, a Live Microbiota-based Biotherapeutic, Improves Outcomes of Clostridioides difficile Infection in a Real-World Population: A Retrospective Study of Use Under Enforcement Discretion,” was accepted as an abstract for the Making a Difference in Infectious Diseases (MAD-ID) 2022 Annual Meeting.