A Randomized, Double-Blind, Phase 3 Safety and Efficacy Study of Ridinilazole Versus Vancomycin for Treatment of Clostridioides difficile Infection: Clinical Outcomes With Microbiome and Metabolome Correlates of Response

BACKGROUND

Exposure to antibiotics predisposes to dysbiosis and Clostridioides difficile infection (CDI) that can be severe, recurrent (rCDI), and life-threatening. Nonselective drugs that treat CDI and perpetuate dysbiosis are associated with rCDI, in part due to loss of microbiome-derived secondary bile acid (SBA) production. Ridinilazole is a highly selective drug designed to treat CDI and prevent rCDI.

METHODS

In this phase 3 superiority trial, adults with CDI, confirmed with a stool toxin test, were randomized to receive 10 days of ridinilazole (200 mg twice daily) or vancomycin (125 mg 4 times daily). The primary endpoint was sustained clinical response (SCR), defined as clinical response and no rCDI through 30 days after end of treatment. Secondary endpoints included rCDI and change in relative abundance of SBAs.

RESULTS

Ridinilazole and vancomycin achieved an SCR rate of 73% versus 70.7%, respectively, a treatment difference of 2.2% (95% CI: -4.2%, 8.6%). Ridinilazole resulted in a 53% reduction in recurrence compared with vancomycin (8.1% vs 17.3%; 95% CI: -14.1%, -4.5%; P = .0002). Subgroup analyses revealed consistent ridinilazole benefit for reduction in rCDI across subgroups. Ridinilazole preserved microbiota diversity, increased SBAs, and did not increase the resistome. Conversely, vancomycin worsened CDI-associated dysbiosis, decreased SBAs, increased Proteobacteria abundance (∼3.5-fold), and increased the resistome.

CONCLUSIONS

Although ridinilazole did not meet superiority in SCR, ridinilazole greatly reduced rCDI and preserved microbiome diversity and SBAs compared with vancomycin. These findings suggest that treatment of CDI with ridinilazole results in an earlier recovery of gut microbiome health. Clinical Trials Registration.Ri-CoDIFy 1 and 2: NCT03595553 and NCT03595566.

730. A Phase 3, Randomized, Double-Blind Study to Evaluate the Efficacy and Safety of Ridinilazole Compared with Vancomycin for the Treatment of Clostridioides difficile Infection

Background

Vancomycin (VAN) therapy for C. difficile infection (CDI) is effective with > 80% clinical response (CR) but is associated with 20–30% recurrence rate (rCDI). Secondary bile acids (2° BAs) inhibit C. difficile germination and help prevent rCDI. VAN depletes the gut microbiome decreasing the conversion of primary bile acids to 2° BAs. Ridinilazole (RDZ) is a highly selective anti-CDI, DNA-binding antibiotic in development for the treatment of CDI and prevention of rCDI.

Methods

A global, double-blinded, randomized Phase 3 trial assessed a 10-day treatment with RDZ 200 mg BID vs VAN 125 mg QID for CDI. The primary endpoint was sustained clinical response (SCR) defined as CR and no rCDI through 30 days post-end of treatment (EOT). Other endpoints included rCDI, microbiome diversity and composition, and microbiome-derived 2° BAs concentration. rCDI was defined as a new episode of diarrhea with confirmed positive free toxin test (FTT), requiring additional CDI therapy. All participants were monitored for treatment emergent adverse events (TEAE).

Results

Of the 759 patients (pts) enrolled, 745 were included in the mITT population (RDZ n=370, VAN n=375). RDZ achieved a numerically higher SCR rate than VAN (73.0% vs 70.7%) p=0.4672. RDZ resulted in a significant reduction in rCDI rate (8.1% vs 17.3%, p=0.0002) (Fig 1). In a pre-specified subpopulation, this was most notable in pts not receiving other antibiotics (rCDI 6.7% in RDZ vs 16.5% in VAN, p=0.0005). Microbiome alpha diversity was higher for RDZ vs VAN at EOT and EOT+30d (p< 0.0001 and p≤ 0.0007 respectively, Fig 2) as were relative abundance (p< 0.0001 and p=0.0203 respectively), and concentrations of 2° BAs (Fig 3). Higher microbiome diversity and concentrations of 2° BAs at EOT were associated with both lower rCDI and higher SCR rates. RDZ was well tolerated (pts with ≥ 1 TEAE: RDZ 36.4% vs VAN 35.5%, treatment discontinuation due to TEAE: RDZ 0.8% vs. VAN 2.9%).

Conclusion

RDZ was effective for sustained clinical response and safe for the treatment of patients with CDI. This was most notable in pts not receiving antibiotics. Compared to VAN, RDZ patients had faster recovery of fecal 2° BA, consistent with the preservation of microbiome diversity, resulting in a significantly lower rate of rCDI.

Disclosures

Pablo C. Okhuysen, MD, AstraZeneca: Stocks/Bonds|Beam Therapeutics: Stocks/Bonds|Biontech: Stocks/Bonds|Deinove: Grant/Research Support|Ferring: Advisor/Consultant|Glaxo Smith Kleine: Stocks/Bonds|Johnson and Johnson: Stocks/Bonds|Melinta: Grant/Research Support|Merck Sharp & Dohme Corp: Grant/Research Support|Moderna: Stocks/Bonds|Napo Pharmaceuticals: Advisor/Consultant|Napo Pharmaceuticals: Grant/Research Support|Novavax: Stocks/Bonds|Pfizer: Stocks/Bonds|Summit: Advisor/Consultant|Summit: Grant/Research Support Kevin W. Garey, PharmD, MS, Acurx: Grant/Research Support|cidara: Advisor/Consultant|cidara: Grant/Research Support|Paratek: Grant/Research Support|Seres Health: Grant/Research Support|Summit: Grant/Research Support Thomas J. Louie, MD, adiso therapeutics: Advisor/Consultant|adiso therapeutics: Grant/Research Support|crestone: Advisor/Consultant|crestone: Grant/Research Support|Finch: Advisor/Consultant|Finch: Grant/Research Support|Seres Therapeutics: Advisor/Consultant|Seres Therapeutics: Grant/Research Support|Seres Therapeutics: Honoraria|summit plc: Grant/Research Support|vedanta biosciences: Advisor/Consultant|vedanta biosciences: Grant/Research Support Jianling LI, MS, Abbott: Stocks/Bonds|Abbvie: Stocks/Bonds|ALX Oncology: Stocks/Bonds|BioNTech: Stocks/Bonds|Bluebird Bio: Stocks/Bonds|Cytokinetics: Stocks/Bonds|I-Mab: Stocks/Bonds|Johnson & Johnson: Stocks/Bonds|Moderna: Stocks/Bonds|TG Therapeutics: Stocks/Bonds Esther Duperchy, PhD, Summit Plc: Employee Jose G. Montoya, MD, Summit: Honoraria|Summit: Stocks/Bonds Lori Styles, MD, Abbvie: Stocks/Bonds|Summit Therapeutics: employee|Summit Therapeutics: Stocks/Bonds Fong Clow, Sc. D, Summit Therapeutics: Employee Danelle James, MD, Summit Therapeutics: Employee.