Dana Walsh PhD1, Carlos Gonzalez MS2, Bill Shannon PhD MBA2, Ken Blount1
1Rebiotix Inc, Roseville, MN, USA; 2BioRankings, St. Louis, MO, USA
Antimicrobial resistance (AMR) is a challenge in individuals at risk for recurrent Clostrioides difficile infection (rCDI). Recognizing that AMR bacteria colonize the intestinal microbiota, therapeutic approaches that decolonize the gut of AMR bacteria would be valuable. Herein, we assessed the microbial resistome before and after treatment with RBX7455—a room temperature-stable, orally-administered investigational microbiota-based therapeutic—in a Phase 1 trial for reducing CDI recurrence.
Ninety percent of participants met the primary endpoint of no CDI recurrence through 8 weeks after treatment, and participant microbiome compositions became more similar to RBX7455 after treatment. The total AMR counts per participant decreased from before to after treatment (p<.05, mixed effects model), with the pattern of AMRs identified (resistome) becoming more like the RBX7455 resistome (Figure 1). Most notably, AMRs associated with multi-drug, fluoroquinolone, and betalactam resistance decreased from before to after treatment. There was no significant difference among the groups with respect to clinical response or changes in microbiome composition and AMR content.
Among 5 trials with consistent investigational product and clinical endpoints, RBX2660 consistently reduced rCDI recurrence, with a majority of treatment responders remaining CDI-free for at least 6 and up to 24 months. Further, initial lIn a Phase 1 trial of RBX7455 for rCDI, AMR gene content decreased after treatment. This underscores the potential of microbiota-based therapies for decolonizing AMR bacteria from the gut microbiota. Continued clinical evaluation of RBX7455 is underway.
Figure 1 – Average total and per-class AMR gene counts in participant samples before and after RBX7455 treatment.