Clinical Trials

Inclusion Criteria:

• Ability to provide written informed consent.
• Men or women 18 years of age or older.
• Recurrent CDI* as defined by:
  • 3 episodes of CDI, with 2 episodes occurring within the previous 12 months (inclusive of the current episode); OR
  • 2 episodes of CDI occurring within the previous 6 months (inclusive of the current episode) AND 65 years of age or older;
  • *NOTE: CDI is defined by: 
    • History of diarrhea (≥ 3 unformed stools per day) for 2 or more consecutive days; AND
    • A stool specimen documented as testing positive for C. difficile within 60 days prior to Randomization. Testing for CDI may include:
      • Presence of toxin A and/or B of C. difficile in the stool determined by any locally available Food and Drug Administration (FDA)-cleared test of C. difficile toxin including the Alere C. DIFF QUIK CHEK COMPLETE rapid test, enzyme immunoassay for cytotoxin, or toxigenic culture; AND/OR
      • Presence of a toxigenic strain of C. difficile determined by a locally available FDA-cleared nucleic acid amplification test (NAAT) to detect the presence of either toxin genes or the pathogenicity locus, or non-FDA-cleared tests that have been approved by the Sponsor.
        • NOTE: Subjects < 65 years who only have a NAAT/PCR positive test alone (not part of multi-step testing algorithm) within 60 days prior to Randomization may be randomized after consultation with the Medical Monitor; AND
      • Has received a course of standard-of-care CDI antibiotics for the most recent CDI episode (for 10-42 days, with exact duration, antibiotic type, and dose at the discretion of the Investigator); AND
      • Has an adequate clinical response, defined as ≥ 3 unformed stools in 24 hours for 2 or more consecutive days during standard-of-care CDI antibiotics prior to Randomization.
• Willingness to abstain from consuming non-dietary probiotics through Week 8 after Randomization.
• Women must fulfill at least 1 of the following criteria:
  • Post-menopausal, defined as amenorrhea ≥ 1 year;
  • Surgically sterile: hysterectomy, bilateral oophorectomy, or tubal ligation; or
  • Abstinent or willing to use adequate contraception from Screening through the Week 24 visit; and
• Deemed to have life expectancy of 8 weeks or greater.

Exclusion Criteria:

• Admitted to, or expected to be admitted to, an intensive care unit for any medical reason.
  • NOTE: Residents of long term care facilities, such as nursing homes and rehabilitation centers, are eligible for study entry.
  • NOTE: Patient visits to clinics, urgent care centers, acute care hospitals, or emergency departments are allowed; however, subject must be an outpatient prior to Randomization.
• Stools known to be positive for ova and/or parasite(s), or other enteric pathogens (e.g., Salmonella, Shigella, and/or Campylobacter) within 28 days prior to Screening.
• Inability to ingest capsules (e.g., severe nausea, vomiting, and/or dysphagia).
• Known or suspected toxic megacolon and/or known small bowel ileus.
• Prior history, evidence, or diagnosis of inflammatory bowel disease (e.g., Crohn’s disease, ulcerative colitis, indeterminate colitis, or microscopic colitis).
• Recent diagnosis (< 6 months prior to Screening) of diarrhea-predominant irritable bowel syndrome (post-infection or not related to an enteric infection). Subjects with diarrhea-predominant irritable bowel syndrome  6 months prior to Screening may be randomized after consultation with the Medical Monitor.
• Current diagnosis of chronic diarrheal illness with pre-CDI baseline diarrhea (≥ 3 loose stools in a 24-hour period). This includes but is not limited to celiac disease, bile salt diarrhea, chronic pancreatitis, and short gut syndrome.
• Past administration of bezlotoxumab (Zinplava™), or past enrollment in a C. difficile vaccine study within 12 months of Randomization.
• Initiation of any systemic cancer treatment (e.g., chemotherapy, radiotherapy, biologic, others) for active malignancy that is planned 8 weeks prior to Randomization or during the 8 weeks following Randomization. Subjects on maintenance treatment for malignancy may be randomized after consultation with the Medical Monitor.
• Initiation or escalation of immunosuppressive agents, at the discretion of the Investigator, for any condition during the 8 weeks prior to Randomization or planned during the 8 weeks following Randomization. Subjects on stable immunosuppressive agents or short-courses may be randomized after consultation with the Medical Monitor.
  • NOTE: Solid organ transplant recipients are excluded.
• Compromised immune system, including, but not limited to, a known history of human immunodeficiency virus infection and cluster of differentiation 4 count that is unknown or documented to be < 200 cells/mm^3 within the last year, or an acquired immunodeficiency syndrome-defining illness; or at the discretion of the Investigator.
• Fecal transplant for any condition, regardless of route of administration, in the last year or plans to undergo during the study.
• Major intra-abdominal surgery (e.g., bowel resection) within the past 60 days prior to Screening (excluding appendectomy or cholecystectomy), history of total colectomy/ileostomy and/or planned invasive surgery/hospitalization during the study;
  • NOTE: Subjects with history of bariatric surgery may be randomized after consultation with the Medical Monitor.
• Use of a systemic antibiotic for any condition (other than CDI therapy for the current recurrence) during the Screening period, or any anticipated use of a systemic antibiotic for any condition other than CDI during the study for 8 weeks after Randomization. This includes subjects who have a known medical procedure that requires antibiotic prophylaxis (e.g., elective surgical procedure or dental procedure requiring prophylactic antibiotics) scheduled during the study.
• Unable to discontinue drugs that are specifically used as antiperistaltic agents (e.g., intended to control diarrhea, including but not limited to loperamide, diphenoxylate-atropine, or opioids).
  • NOTE: Opioids prescribed for chronic pain or other indications are allowed if stable dose or decreasing dose during the course of the study. Changes in regimen should be discussed with the Medical Monitor.
• Active drug, chemical, or alcohol dependency as determined by the Investigator through history or optional toxicology screen.
• Enrollment in any other investigational drug or device study within 30 days prior to Randomization (Day 1) or within 5 half-lives of the last dose of the previous investigational compound, whichever is longer.
• Pregnant, breast-feeding, or considering becoming pregnant during the study.
• Clinically significant abnormal laboratory values including, but not limited to, white blood cell count ≥ 15 x 10^9 laboratory evidence of acute kidney injury, or absolute neutrophil count of < 1 x 10^9 neutrophils at Screening.
• Any acute or chronic medical comorbidity, psychiatric, social, or other circumstances that, in the opinion of the Investigator, may interfere with study compliance, completion, or accurate assessment of study outcomes/safety.

Randomization (Day 1) Inclusion Criteria:

• An outpatient prior to Randomization.
  • NOTE: Subject may be enrolled while an inpatient in an acute care facility, but must be discharged prior to Randomization on Day 1. Subjects residing in an assisted living center, long-term care facility, or rehabilitation center may be randomized.
• Has received a course of standard-of-care CDI antibiotics for the most recent CDI episode (for 10-42 days, with exact duration, antibiotic type, and dose at the discretion of the Investigator).
• Has an adequate clinical response, defined as ≤ 3 unformed stools in 24 hours for 2 or more consecutive days during standard-of-care CDI antibiotics prior to Randomization.
• Subject has completed a washout (i.e., a minimum of 2 and a maximum of 6 days after cessation of standard-of-care CDI antibiotics). If the subject experiences diarrhea for 2 or more consecutive days during the washout period, the Investigator should contact the Medical Monitor.