Conference Coverage

A pill for C. difficile works by increasing microbiome diversity


AT ACG 2021

Understanding how it works

To understand better how CP101 achieves its effects, the researchers collected stool samples from the patients and counted the number of different kinds organisms in each sample.

At baseline, the patients had about the same number, but after a week the diversity was greater in the patients treated with CP101, and that difference had increased at week 8. The researchers also found much less diversity of organisms in the stools of those patients who had recurrences of C. difficile infection.

The diversity of microbes in the successfully treated patients appeared to have been introduced by CP101. Dr. Allegretti and colleagues measured the number of organisms in the stool samples that came from CP101. They found that 96% of patients colonized by the CP101 organisms had avoided recurrence of the C. difficile infections, compared with 54.2% of those patients not colonized by these microbes.

“We now have some microbiome-based markers that show us as early as week 1 that the patient is going to be cured or not,” Dr. Allegretti said.

Based on these results, Finch plans to launch a phase 3 trial soon, she said.

The data on colonization is interesting because it has not been found with fecal microbiota transplants, said Purna Kashyap, MBBS, codirector of the Microbiome Program at the Mayo Clinic College of Medicine in Rochester, Minn., who was not involved in the study.

But to better interpret the data, it would be helpful to know more about how the placebo and CP101 groups compared at baseline with regard to medications, immunosuppression, and antibiotics used to treat the C. difficile infections, Dr. Kashyap said. He was struck by the lower cure rate in the portion of the placebo group treated with fidaxomicin.

“Overall, I think these are exciting observations based on the data but require careful review of the entire data to make sense of [them], which will happen when it goes through peer review,” he told this news organization in an email.

Several other standardized microbiota restoration products are under development, including at least two other capsules. In contrast to CP101, which is made up of whole stool, VE303 (Vedanta Biosciences) is a “rationally defined bacterial consortium,” and SER-109 (Seres Therapeutics) is a “consortium of highly purified Firmicutes spores.” VE303 has completed a phase 2 trial, and SER-109 has completed a phase 3 trial.

Dr. Allegretti is a consultant for Finch Therapeutics, which funded the trial. Dr. Kashyap has disclosed no relevant financial relationships.

A version of this article first appeared on


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