The objective of this Phase IIa study is to assess the safety, tolerability, and efficacy of incremental doses of MGB-BP-3 in patients with Clostridium difficile-associated diarrhea (CDAD).

This is an exploratory, Phase IIa, open-label study assessing the safety, tolerability, and efficacy of incremental doses of MGB-BP-3 with 3 sequential groups of 10 patients with CDAD. Patients will be administered an oral dose of MGB-BP-3 for 10 days (Day 1 to Day 10). At the end of the treatment period, patients will be followed for up to 8 weeks to assess the incidence of disease recurrence.

Main Inclusion Criteria:

1. Age 18 years or older of any gender.
2. Inpatients and/or outpatients who are able to attend all scheduled visits.
3. Patients with the first episode or the first recurrence of mild or moderate CDAD.
4. Confirmed diagnosis of mild or moderate CDAD as defined by the Infectious Diseases Society of America/Society for Healthcare Epidemiology of America guidelines.

Main Exclusion Criteria:

1. Patients with severe complicated CDAD (including hypotension or shock, ileus, megacolon, pseudomembranous colitis).
2. A white blood cell count higher than 15,000 cells/mL.
3. A serum creatinine level greater than or equal to 1.5 times ULN.
4. Elevated liver enzymes alanine aminotransferase and aspartate aminotransferase greater than ULN.
5. Inflammatory bowel disease (ulcerative colitis or Crohn's disease), microscopic colitis, or irritable bowel syndrome with chronic diarrhea.
6. Any other non-C difficile diarrhea.
7. Received treatment with a fecal transplant within 7 days and/or is anticipated to receive a fecal transplant during the study.
8. Major gastrointestinal surgery (ie, significant bowel resection) within 3 months of enrollment (does not include appendectomy or cholecystectomy).
9. Received laxatives within the previous 48 hours.
10. Pregnant or lactating women.
11. Prior (within 180 days of Screening) or current use of anti-toxin antibodies.
12. Have received a vaccine against C difficile.
13. Any condition for which, in the opinion of the investigator, the treatment may pose a health risk to the patient.