SER-262 Versus Placebo in Adults With Primary Clostridium Difficile Infection to Prevent Recurrence

SER-262-001 is a Phase 1b, randomized, double blind, placebo-controlled, ascending single
dose clinical study with 2 treatment arms (SER-262 or placebo) in up to 8 dose cohorts.
Patients who have been diagnosed with their first (primary) episode of CDI, defined as
diarrhea (≥ 3 unformed stools per day for 2 consecutive days), a positive C. difficile stool
test and who have responded to standard‑of‑care antibiotic will receive investigational drug
or placebo on Day 1.

Inclusion Criteria:

1. Signed informed consent, indicating that the subject understands the purpose of and
procedures required for the study.

2. Male or female subjects ≥ 18 years.

3. A primary (first) episode of CDI with documentation of the episode including CDI date,
test results, antibiotic treatment (including start and stop dates), and response to
treatment

Exclusion Criteria:

1. Females who are pregnant, breastfeeding, lactating, or planning to become pregnant
during the study.

2. Known or suspected toxic megacolon and/or known small bowel ileus.

3. Active irritable bowel syndrome with diarrhea within the previous 12 months.

4. Major gastrointestinal surgery (eg, significant bowel resection or diversion) within 3
months before enrollment (this does not include appendectomy or cholecystectomy) or
any history of total colectomy or bariatric surgery.

5. History of inflammatory bowel disease (ulcerative colitis, Crohn's disease,
microscopic colitis) with diarrhea believed to be caused by active inflammatory bowel
disease in the past 12 months.

6. Estimated glomerular filtration rate (eGFR) < 60 ml/min/1.73m2

7. Admitted to or expected to be admitted to an intensive care unit for medical reasons
(not just boarding). Patients discharged from an intensive care unit before Day 1 may
be enrolled.

8. Concurrent intensive induction chemotherapy, radiotherapy, or biologic treatment for
active malignancy (patients on maintenance chemotherapy may only be enrolled after
consultation with medical monitor).

9. Absolute neutrophil count < 500 cells/mm3