for people ages 18 years and up (full criteria)
at La Jolla, California and other locations
study started
estimated completion



Summit is developing ridinilazole as a novel antimicrobial for Clostridium difficile Infection (CDI) with the goal of achieving comparable cure rates to standard of care, but reducing rates of recurrent disease. A phase 2 proof of concept study, with vancomycin as comparator, demonstrated these attributes with a comparable safety profile. A high fecal concentration of ridinilazole and little systemic exposure were noted. The rationale for this phase 3 study is to confirm the improvement in sustained clinical response of CDI over vancomycin and to compare the safety and tolerability of ridinilazole to that of vancomycin.

Official Title

A Phase 3, Randomized, Double-blind, Active Controlled Study to Compare the Efficacy and Safety of Ridinilazole (200 mg, Bid) for 10 Days With Vancomycin (125 mg, Qid) for 10 Days in the Treatment of Clostridium Difficile Infection (CDI)


Clostridium Difficile Infection Infection Communicable Diseases Clostridium Infections Enterocolitis, Pseudomembranous Vancomycin ridinilazole


You can join if…

Open to people ages 18 years and up

  1. At least 18 years of age, at the time of signing the informed consent.
  2. Signs and symptoms of CDI including diarrhea such that in the Investigator's opinion CDI antimicrobial therapy is required. Diarrhea is defined as a change in bowel habits, with ≥3 Unformed Bowel Movements (UBMs) (5, 6 or 7 on the Bristol Stool Chart) in the 24 h prior to randomization.
  3. The presence of either toxin A and/or B of C. difficile in the stool determined by a positive free toxin test, produced within 72 hours prior to randomization.
  4. Male or Female
  5. Male must agree to use contraception as detailed in the protocol during the treatment period and for at least 5 days after study treatment and refrain from donating sperm during this period.
  6. Female patient is eligible to participate if she is not pregnant, not breastfeeding, and either:

Not a woman of childbearing potential (WOCBP). A WOCBP who agrees to follow the contraceptive guidance per protocol during the treatment period and for at least 5 days after study treatment.

  1. Documented signed informed consent and any authorizations required by local law (e.g. Protected Health Information [PHI]).

You CAN'T join if...

  1. More than one prior episode of CDI in the previous 3 months or more than 3 episodes in the past 12 months.
  2. A history of chronic diarrheal disease including inflammatory bowel disease (Crohn's disease or ulcerative colitis).
  3. Positive diagnostic test for other gastro intestinal (GI) pathogens within 2 weeks of randomization.
  4. Major gastrointestinal (GI) surgery (e.g. significant bowel resection) within 3 months of randomization (except appendectomy). Presence of a colostomy or ileostomy or likely requirement of an ostomy during the study.
  5. Life threatening or fulminant CDI with evidence of hypotension, septic shock, peritoneal signs or absence of bowel sounds, or toxic megacolon.
  6. Current history of significantly compromised immune system e.g.:
  7. HIV positive with a CD4<200 cells/mm3 within 6 months of randomization.
  8. Severe neutropenia with neutrophil count < 500 cells/mL.
  9. Concurrent immunosuppressive therapy for recent (within previous 6 months) or anticipated solid organ transplant or bone marrow transplant.
  10. Concurrent chemotherapy, radiotherapy or biologic for active malignancy. Or active malignancy with ablative chemotherapy within the past 3 months or anticipated during the study.
  11. More than one day (24 hours) of dosing of antimicrobial treatment active against CDI for the current episode of CDI prior to randomization.
  12. Prior or current use of anti-toxin antibodies including bezlotoxumab.
  13. Unable to discontinue products used to affect bowel movement or disease progression.
  14. . Involved in a clinical trial and received an IMP for indications other than CDI within 1 month or five half-lives (whichever is longer) or within 3 months if the IMP was for CDI.
  15. . Received an investigational vaccine against C.difficile.
  16. . Patients that the Investigator feels are inappropriate for the study for any other reason e.g. have any conditions that would make the patient unsuitable for inclusion, patients not likely to complete the study for whatever reason, known hypersensitivity or intolerance to study IMPs, patients unwilling or unable to comply with protocol requirements


  • U.C.S.D. accepting new patients
    La Jolla California 92093 United States
  • eStudySite accepting new patients
    Chula Vista California 91911 United States


accepting new patients
Start Date
Completion Date
Summit Therapeutics
Phase 3
Study Type
Last Updated