• Ridinilazole treatment resulted in a 59% reduction in recurrence compared to vancomycin
• C. difficile causes approximately 500,000 infections and 29,000 deaths in the US annually
• There are at least 12 products in development that target the microbiome in treating C. difficile

Summit Therapeutics plc (NASDAQ: SMMT, AIM: SUMM) announced on 8/3/2018 the publication in the journal PLOS ONE of microbiome analyses highlighting ridinilazole as a precision antibiotic in development for the treatment of C. difficile infection (‘CDI’).

The clinical management of CDI is stymied by poor sustained cures due to high recurrence rates after initial infection. The microbiome is known to play an important role in protecting against initial CDI and the onset of recurrent disease. Thus, preserving the microbiome could help to address the key unmet need in CDI. In a double-blind Phase 2 clinical trial, ridinilazole was highly preserving of patients’ microbiomes compared to patients treated with the broad-spectrum standard of care antibiotic vancomycin. With this microbiome preservation, ridinilazole treatment resulted in a 59% reduction in recurrence compared to vancomycin (14.3% vs. 34.8%, respectively). Ridinilazole also demonstrated clinical and statistical superiority over vancomycin in sustained clinical response, which captures whether patients have been cured and remain free from disease recurrence 30 days after completing treatment. 

“These results show how the precision action of ridinilazole against C. difficile, and its corresponding lack of impact on the broader microbiome, led to greatly increased rates of sustained cures through decreased disease recurrence. Better prevention of recurrence is the next frontier in CDI therapy, with potential to reduce both patient morbidity and healthcare costs, which escalate further when initial treatment fails,” commented Dr David Roblin, President of R&D of Summit.“Ridinilazole exemplifies Summit’s strategy of developing new mechanism antibiotics we believe may have the potential to become new standards of care for serious bacterial infections.”

In the US alone, C. difficile causes approximately 500,000 infections and 29,000 deaths annually. Patients typically develop CDI following the use of broad-spectrum antibiotics that can cause widespread damage to the natural gut microbiome and allow overgrowth of C. difficile bacteria. Existing CDI treatments are predominantly broad-spectrum antibiotics, which cause further damage to the microbiome and are associated with high rates of recurrent disease.

Other treatments under development include fecal transplants, specific microbial supplementation, phage therapy. Cafepharma's microbiome database lists 12 microbiome focused therapies currently under development. Seres and Rebiotix both have products in Ph III trials for C. diff.