Study Summary

This study involves research about recurrent Clostridium difficile infection and SER-109 (an investigational medicine). SER-109, is composed of bacterial spores (the inactive form of bacteria) purified from a healthy donor and placed in capsules that are taken orally. These spores are common in the healthy gut but are often depleted in the intestines of C. difficile and ulcerative colitis patients.

This study is to determine if SER-109 will help replenish beneficial bacteria in the intestines and help prevent recurrent C. difficile infection.

The study will involve approximately 320 participants with recurrent Clostridium difficile infection.  The study lasts for 27 weeks. Half of the study participants will receive the investigational medication and the other half will receive placebo. Whether the subject receives the investigational medication or the placebo, the subject will take 4 capsules daily for 3 consecutive days, be observed for 8 weeks, and then engage in a long-term safety follow-up period lasting 16 weeks.

The study includes approximately 6 home or clinic visits and up to 12 phone calls. During the study clinic visits and phone calls, the study staff will perform assessments to evaluate the subject’s health and progress. This includes:

  • Review of the subject’s medical history

  • Physical exams

  • Measurement of vital signs

  • Collection of blood, stool, and urine samples

  • Evaluations of the subject’s diarrheal episodes

  • Review of any medications the subject has taken

  • Review of any side effects the subject has experienced

The study is sponsored by Seres Therapeutics.  Seres Therapeutics will cover the costs of the study treatment, tests, clinic visits, and care provided for the study.

Can I Take Part?


  • Seres Therapeutics (Study Protocol, 20170324 Poster English20170324V1SERES-012RecruitmentBrochureEnglishCMcG, Seres 012PosterEnglish CLIENT REV & QD TRKED.DOCX)