New Data Continues to Show Value in RBX2660 for rCDI

Published on: 

Strategic Alliance Partnership | <b>Mayo Clinic Gastroenterology and Hepatology</b>

More than 70% of patients treated with RBX2660 were recurrence free at the 8 week mark.

New data shows RBX2660 helps reduce recurrent Clostridioides difficile infections (rCDI) following standard-of-care antibiotic treatment in a Bayesian analysis model.

A team, led by Sahil Khanna, MBBS, MS, Mayo Clinic, presented new data from the PUNCH CD3 study evaluating a RBX2660, a live microbiota therapeutic.

The Trial

In the randomized, double-blind, placebo-controlled phase 3 trial, the investigators examined 267 patients with recurrent CDI infections. Of this group, approximately a third were treated at first recurrence (n = 180, RBX2660; n = 67, placebo).

The investigators sought primary endpoints of treatment success, defined as the absence of CDI diarrhea within 8 weeks following treatment.

Each patient had 1 or more C difficile infection recurrences with a positive stool assay and were previously treated with standard-of-care antibiotics.


The results show an original Bayesian analysis model estimation of treatment success of 70.4% at 8 weeks in the RBX2660 cohort, compared to 58.1% for the placebo group. There was a 99.1% posterior probability that RBX2660 was superior to placebo in reducing rCDI following standard-of-care antibiotic treatment.

However, the investigators then aligned the data to improve the exchangeability and interpretability of the Bayesian analysis and found the model-estimated treatment success rate for the treatment group was 70.6% compared to 57.5% for the placebo group.

There was a 99.1% posterior probability that RBX2660 was superior to placebo in reducing rCDI following standard-of-care antibiotic treatment and there was an estimated treatment effect of 13.1%.

The numbers were even more impressive at 6 months, where more than 90% of participants who achieved treatment success remained free of rCDI.


For safety, the majority of adverse events were mild-to-moderate in nature, with no treatment-related serious adverse events identified. However, treatment-emergent adverse events were higher in the RBX2660 group compared to placebo (55.6%, n = 100, RBX2660; 44.8%, n = 39, placebo). This was largely caused by a higher incidence rate of mild gastrointestinal events in the RBX2660 group.

“The findings from this Phase 3 trial provide hope that this potential treatment could make a meaningful difference in the lives of patients with recurrent C. difficile infection,” Khanna said in a statement.

Data From ACG

Data from the ad-hoc analysis of the ongoing, single-arm, PUNCH-CD3 open-label phase 3 study was recently presented at the American College of Gastroenterology (ACG) 2022 Annual Scientific Meeting in Charlotte.

The investigators, once again led by Khanna, found 74.6% (n = 300) treated with RBX2660 remained free of a CDI recurrence.Moreover, at 6 months, 84% of assessable patients (n = 220) experienced a sustained response and remained CDI recurrence free.

The Future

RBX2660 has received fast track, orphan, and breakthrough therapy designations from the FDA.

In September 2022, the FDA's Vaccines and Related Biological Products Advisory Committee (VRBPAC) recommended approval for a biologics license application (BLA) for the single-dose microbiota-based live biotherapeutic product to treat recurrent CDI. The BLA is currently pending a decision from the FDA.

The study, “Efficacy and Safety of RBX2660 in PUNCH CD3, a Phase III, Randomized, Double‑Blind, Placebo‑Controlled Trial with a Bayesian Primary Analysis for the Prevention of Recurrent Clostridioides difcile Infection,” was published online in Drugs.