Jones, Courtney

Abstract Background Recurrent Clostridioides difficile infections (rCDI) are a global public health threat. To reduce rCDI, microbiota-restoring therapies are needed, particularly standardized, easy-to-administer formulations. Methods This phase I open-label trial assessed the safety, efficacy in preventing rCDI recurrence, and intestinal microbiome effects of RBX7455, a room temperature-stable, orally administered investigational live biotherapeutic. Adult participants with 1 or more prior episodes of rCDI received: 4 RBX7455 capsules twice daily for 4 days (group 1); 4 RBX7455 capsules twice daily for 2 days (group 2); or 2 RBX7455 capsules twice daily for 2 days (group 3). For all groups, the first dose was administered in clinic, with remaining doses self-administered at home. Adverse events were monitored during and for 6 months after treatment. Treatment success was defined as rCDI prevention through 8 weeks after treatment. Participants’ microbiome composition was assessed prior to and for 6 months after treatment. Results Nine of 10 group 1 patients (90%), 8 of 10 group 2 patients (80%), and 10 of 10 group 3 patients (100%) were recurrence-free at the 8-week endpoint with durability to 6 months. Seventy-five treatment-emergent adverse events were observed in 27 participants with no serious investigational product-related events. Prior to treatment, participants’ microbiomes were dissimilar from the RBX7455 composition with decreased Bacteroidia- and Clostridia-class bacteria, whereas after treatment, responders’ microbiomes showed increased Bacteroidia and Clostridia. Conclusions Three dosing regimens of RBX7455 were safe and effective at preventing rCDI. Responders’ microbiomes converged toward the composition of RBX7455. These results support its continued clinical evaluation. Clinical Trials Registration NCT02981316.

Abstract Background Recurrent Clostridium difficile infections (rCDI) are associated with decreased diversity and altered intestinal microbiome compared with healthy patients. RBX2660, a standardized microbiota-based drug, is designed to restore microbiome diversity and composition in patients’. The effect of RBX2660 on rCDI patient microbiomes was evaluated by comparing pre- and post-treatment samples from PUNCH CD 2—a randomized, double-blind, placebo-controlled study. Methods rCDIsubjects were randomized to receive blinded treatments of 2 doses of RBX2660 (Group A), 2 doses of placebo (Group B), or 1 dose each of RBX2660 and placebo (Group C), by enema 7 days apart. Subjects submitted stool samples at baseline, day 7, 30, and 60 after treatment. Stool samples from responders to RBX2660 treatment per protocol defined as the absence of CDI for 8 weeks after treatment were compared with non-responders. Relative taxonomic abundances at the class level were determined using 16s rRNA sequencing analysis for 94 stool samples from 45 patients in Groups A and C. Relative abundance data were grouped longitudinally using Bray-Curtis dissimilarity index. Analyses were performed based on the Dirichlet-Multinomial distribution to compare group mean relative taxonomic abundances; Simpson and Shannon diversity indices were compared among groups longitudinally. Results Baseline patient microbiomes were similar across response groups. RBX2660 treatment shifted the relative microbiome densities with taxa-specific increase in Bacteroidia, Clostridia, and decrease in Gamma-proteobacteria abundance. A larger shift from baseline microbiome was seen in responders to RBX2600 compared with non-responders (Figure 1). Microbiome changes in responders were durable to 60 days. RBX2660 treatment increased Shannon and Simpson diversity at 7 days post-treatment in responders but not in non-responders (P < 0.05). Conclusion RBX2660 treatment shifts patient intestinal microbiomes with greater alterations seen in those with a successful clinical outcome. Funded by Rebiotix Inc., Roseville, MN. Disclosures S. Khanna, Rebiotix, Inc.: Scientific Advisor, Consulting fee; K. Blount, Rebiotix, Inc.: Employee, Salary; C. Jones, Rebiotix, Inc.: Employee, Salary; B. Shannon, Rebiotix, Inc.: Research Contractor, Consulting fee; S. Carter, Rebiotix, Inc.: Research Contractor, Consulting fee