Cohort 1 is an open-label extension of study SERES-012. Subjects who had a CDI recurrence in study SERES-012 within 8 weeks of receipt of study drug, have responded to a course of standard of care (SOC) antibiotic treatment, will receive an oral dose of SER-109. A treatment regimen of SER-109 is defined as an oral dose of SER-109 (4 capsules once daily) for 3 consecutive days.~Approximately 30 eligible subjects with recurrent CDI disease from study SERES-012 are expected to enroll. Screening for this study will begin at the Recurrence Visit of Study SERES-012.~Cohort 2 is an open-label program for subjects who were not part of SERES-012. Subjects 18 years of age or older who had one or more CDI recurrence and have responded to a course of antibiotic treatment will receive an oral dose of SER-109. The CDI recurrence must be confirmed by a positive C. difficile stool toxin or polymerase chain reaction (PCR) assay to confirm eligibility. A treatment regimen of SER-109 is defined as an oral dose of SER-109 (4 capsules once daily) for 3 consecutive days.~Approximately 200 eligible subjects with recurrent CDI disease are expected to enroll.
Cohort 1: Subjects who had a Clostridioides difficile infection (CDI) recurrence in study SERES-012 within 8 weeks of receipt of study drug will be eligible. The purpose of this cohort is to assess safety and efficacy of SER-109 in reducing recurrence of CDI in adults who had a CDI recurrence within 8 weeks after receipt of SER-109 or Placebo in study SERES-012.~Cohort 2: Cohort 2 is an open-label program for subjects who were not part of SERES-012. The purpose of this cohort is to describe safety and tolerability of SER-109 in subjects 18 years of age or older with at least a first recurrence of CDI.