Summit Therapeutics’ fix for slow enrollment in its pivotal antibiotic program has created its own problems. Having previously decided to pool subjects in two Clostridium difficile trials, Summit has now revealed the FDA disagrees with its changes.
Massachusetts-based Summit was aiming to deliver data in the second half of 2021 when it enrolled the first patient early in 2019. However, COVID-19 slowed enrollment, causing Summit to end 2020 still needing to recruit almost two-thirds of the participants. Summit withdrew its completion target amid the uncertainty.
With a little more than $100 million in the bank at the end of June, Summit hatched a plan to deliver data without completing enrollment. Last month, Summit outlined plans to combine the 753 patients it had enrolled across the two studies into a single data set. Although each trial is only around halfway to its enrollment target, Summit bet that together they could support a useful analysis.
That bet has received a frosty reception from the FDA. “The FDA does not agree with the change to the primary endpoint that Summit proposed and has subsequently implemented in its ongoing phase 3 Ri-CoDIFy studies when combining the studies,” Summit said in a statement.
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Summit’s stock sank 20% in response to the news, falling to $5.20 in after-hours trading. Despite the FDA opposition, Summit is forging ahead with the combined study with the view to delivering data in the first quarter of next year. Summit expects the top-line results to “best inform all parties as to the next appropriate course of action regarding ridinilazole.”
A lot is resting on the update for Summit and the broader, stumbling effort to restock the arsenal of antibiotics. C. diff infection recurs in up to 25% of people treated with metronidazole or vancomycin, and, once an infection has recurred once, it is more likely to do so again. Dificid, which Merck picked up in its takeover of Cubist Pharmaceuticals, is associated with a lower rate of recurrence, but there remains a need for new treatment options.