Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

The safety of REBYOTA was evaluated in 2 randomized, double-blind clinical studies (Study 1: NCT03244644 and Study 2: NCT02299570) and 3 open-label clinical studies (NCT01925417, NCT02589847, NCT03931941) conducted in the United States and Canada. A total of 978 adults 18 years of age and older with a history of 1 or more recurrences of Clostridioides difficile (CDI) infection and whose symptoms were controlled 24 – 72 hours post-antibiotic treatment were enrolled and received 1 or more doses of REBYOTA; 595 of whom received a single dose of REBYOTA. In the 2 randomized, double-blind clinical studies, 131 adults were originally randomized to receive placebo and 48 crossed over to receive an open-label dose of REBYOTA after additional CDI recurrence. Overall, across the 5 studies, the median age of participants was 64 years and 67.2 % were female. The racial and ethnic distribution was as follows: 93.8% were white, and 2.4% were of Hispanic or Latino ethnicity. No meaningful differences in demographic characteristics occurred across the treatment groups. Study 1 and Study 2 excluded individuals with celiac disease, Inflammatory Bowel Disease, Irritable Bowel Syndrome, and chronic diarrhea. Individuals with these conditions were not excluded from one of the open-label studies (NCT03931941), and individuals with food allergies were not excluded from any of the 5 clinical studies.

Adverse Reactions

Across the 5 clinical studies, participants recorded solicited adverse events in a diary for the first 7 days after each dose of REBYOTA or placebo. Participants were monitored for all other adverse events by queries during scheduled visits, with duration of follow-up ranging from 6 to 24 months after the last dose. In Study 1, a multi-center, double-blind randomized (2:1), placebo-controlled trial conducted in the United States and Canada, 180 adults 18 years of age and older received a single dose of REBYOTA and 87 received placebo. Participants with a recurrence of CDI (rCDI) during the first 8 weeks after receipt of REBYOTA or placebo were censored from analysis at the time of rCDI. During the first two weeks following a dose of REBYOTA or placebo, 34 participants (18.9%) and 24 participants (27.6%) respectively, were censored. Overall, during the 8 week follow up period, 47 REBYOTA recipients (26.1%) and 30 placebo recipients (34.5%) were censored from analysis. In an analysis of solicited and unsolicited adverse events reported in Study 1, the most common adverse reactions (defined as adverse events assessed as definitely, possibly, or probably related to Investigational Product by the investigator) reported by ≥3% of REBYOTA recipients, and at a rate greater than that reported by placebo recipients, were abdominal pain, (8.9%), diarrhea (7.2%), abdominal distention (3.9%), flatulence (3.3%), and nausea (3.3%) (Table 1). 

Most adverse reactions occurred during the first 2 weeks after treatment. After this, the proportion of patients with adverse reactions declined in subsequent 2-week intervals. Beyond 2 weeks after treatment only a few single adverse reactions were reported. Most adverse drug reactions were mild to moderate in severity. No life-threatening adverse reaction was reported.

Serious Adverse Reactions

In a pooled analysis of the 5 clinical studies, 10.1% (60/595) of REBYOTA recipients (1 dose only) and 7.2% (6/83) of placebo recipients reported a serious adverse event within 6 months post last dose of investigational product. None of these events were considered related to the investigational product.