After being recently awarded a contract worth $62M from the US government’s Biomedical Advanced Research and Development Authority (BARDA), Summit Therapeutics has achieved a significant step toward initiating its clinical research program just seven months after outlining plans for Phase III trials for its developmental Clostridium difficile antibiotic, ridinilazole. With this news, the company looks well-positioned to kick-off its Phase III trials in H1 2018, thus securing ridinilazole’s position as the second most advanced developmental antibiotic for CDIs, behind Actelion’s cadazolid.
difficile infections (CDIs) are healthcare-acquired infections (HAIs) that result in diarrhea and can require surgical intervention in severe cases. The emergence of hypervirulent CDI strains in the early 2000s has driven an increase in infection incidence, with one study estimating that CDIs are now the most common HAI in the US. Although current treatment options, such as oral vancomycin, are considered to be effective at stemming the infection, they leave patients vulnerable to recurrences. As a result of the significant unmet need within this disease area, the market size for CDI is set to grow over the next 10 years, and a recent report by GlobalData predicts that the global market for CDI therapeutics will reach $1.7B by 2026, representing a Compound Annual Growth Rate (CAGR) of 10.2% over this time period.
Summit Therapeutics’ ridinilazole is a pipeline antibiotic that is being developed to reduce the risk of infection recurrence in CDI patients. Ridinilazole is a first-in-class antibiotic that is highly selective toward C. difficile. Clinical studies have shown that patients receiving ridinilazole to treat a CDI suffer less collateral damage to their natural gut microbiota, which Summit Therapeutics believed would help reduce the chance of developing further recurrences. This theory appeared to translate well into clinical practice during Phase II trials for ridinilazole, where patients receiving ridinilazole were observed to have a lower rate of infection recurrence than those taking vancomycin.
The main competition for ridinilazole in the CDI market comes from Actelion’s developmental antibiotic, cadazolid, as well as Merck & Co’s currently marketed antibiotic, Dificid (fidaxomicin). Cadazolid was due to complete Phase III trials this year; however, in June, Actelion announced that the drug had failed to reach its primary endpoint in one of two Phase III trials, and it is now unclear how the company plans to proceed with development moving forward. Merck & Co’s Dificid was launched in 2011 and is positioned as an alternative to vancomycin for the treatment of CDIs, offering improved rates of recurrence. However, Dificid has not been able to achieve a significant foothold in the CDI market, with physicians citing the high cost of treatment and the questionable efficacy, which originated from the use of non-inferiority trials during Phase III development, as concerns.
Summit will examine strategies to give ridinilazole a clinical and commercial advantage over both Dificid and cadazolid. The company has already stated its intention to design the Phase III trials to include superiority to vancomycin as a primary end-point, rather than the non-inferiority criteria included in clinical trials for its competitors. It will likely also be looking closely at Merck’s experience with Dificid, which is generally considered by physicians to be too expensive, when it comes to choosing a pricing strategy for ridinilazole. Summit’s ability to utilize cost-effectiveness as a means of positioning ridinilazole as an improvement over vancomycin could make the difference between the product sinking and swimming.