Evaluation of CRS3123 vs. Oral Vancomycin in Adult Patients With Clostridioides Difficile Infection

A Phase 2, Randomized, Double-Blind, Comparator-Controlled, Multicenter Study to Evaluate the Safety and Efficacy of CRS3123 Compared With Oral Vancomycin in Adults With Clostridioides Difficile Infection

The purpose of this research is to evaluate the primary objectives of safety and efficacy (rate of clinical cure) of 2 dosages of CRS3123 (200 mg and 400 mg) administered orally (po) twice daily (bid) and vancomycin administered 125 mg PO 4 times daily (qid) in adults > or equal to 18 years of age with a primary episode or first recurrence of CDI. The study will investigate the plasma concentrations and HRQoL outcomes of CRS3123 and additional efficacy endpoints as secondary objectives.

Study Overview

• Status: Completed
• Conditions: Clostridioides Difficile Infection
• Intervention / Treatment: Drug: CRS3123; Drug: Active Comparator

• Study Type: Interventional
• Enrollment (Actual): 43
• Phase: Phase 2

Contacts and Locations

Study Locations

• Canada
  • Alberta
    • Calgary, Alberta, Canada, T2N2T9
      • 116
  • Ontario
    • London, Ontario, Canada, N6A 4V2
      • 120
• United States
  • California
    • Fullerton, California, United States, 92835
      • 131
    • Lancaster, California, United States, 93534
      • 117
    • Mission Hills, California, United States, 91345
      • 143
    • Orange, California, United States, 92868
      • 138
  • Florida
    • Miami, Florida, United States, 33125
      • 146
    • Miami, Florida, United States, 33144
      • 122
  • Georgia
    • Marietta, Georgia, United States, 30060
      • 140
  • Idaho
    • Idaho Falls, Idaho, United States, 83404
      • 110
  • Illinois
    • Winfield, Illinois, United States, 60190
      • 129
  • Michigan
    • Royal Oak, Michigan, United States, 48073
      • 130
  • Missouri
    • Weldon Spring, Missouri, United States, 63304
      • 139
  • Montana
    • Butte, Montana, United States, 59701
      • 128
  • New York
    • The Bronx, New York, United States, 10467
      • 134
  • North Carolina
    • Chapel Hill, North Carolina, United States, 27514
      • 147
  • Pennsylvania
    • Uniontown, Pennsylvania, United States, 15401
      • 114
  • Texas
    • Cedar Park, Texas, United States, 78613
      • 104
    • Houston, Texas, United States, 77079
      • 123
    • San Antonio, Texas, United States, 78229
      • 101

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 14 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria

1. Adults, ≥ 18 years of age.
2. More than or equal to 3 diarrheal (Bristol Stool Scale scores 5, 6, or 7) stools/day in a 24-hour period during screening prior to randomization and in the judgment of the investigator that C. difficile is the likely causative agent for the diarrhea.
3. Stool positive for C. difficile Toxin A and/or B antigen using an FDA or Health Canada approved/cleared EIA or ELISA laboratory test.
4. Participants with a primary episode or first recurrence of CDI are eligible.
5. In the judgment of the investigator, the expectation that the participant will survive with effective antibiotic therapy and appropriate supportive care for the anticipated duration of the study.
6. Female participants of childbearing potential must not be pregnant, plan to become pregnant during the study, or be breastfeeding; and must be willing to commit to either sexual abstinence or use highly effective methods of birth control contraception from screening through Day 70.
7. Males must use a condom and spermicide from screening through Day 70 (if the female partner(s) is of childbearing potential) and must not donate sperm from screening through Day 70.
8. Capable of giving signed informed consent, which includes compliance with the requirements and restrictions listed in the informed consent form.

Exclusion Criteria

1. Participants with any of the following conditions:

   1. Intractable vomiting preventing oral medication intake
   2. Severe underlying disease with an expected survival time less than the duration of the study (approximately 70 days).
   3. More than 1 prior CDI occurrence within the last 3 months or more than 2 prior episodes of CDI in the last 12 months.
   4. A history of a recent CDI episode within 3 months prior to enrollment that was non- responsive to vancomycin.
   5. In the investigator's opinion, the participant is anticipated to require oral or intravenous systemic antibiotic therapy for a non-CDI infection between screening and Day 70.
   6. Inflammatory bowel disease (Crohn's disease or ulcerative colitis), uncorrected Hirschsprung's disease, short gut syndrome, or any other condition known to significantly impact bowel motility and/or malabsorption.
   7. Any other known pathogen associated with diarrhea.
   8. Life-threatening or fulminant CDI as defined by IDSA/SHEA Guidelines.
   9. Colonic perforation.
   10. Need for concurrent laxatives or tube feeds, toxin binders, bile acid sequestrants during the study. Microbiota restoration therapy (MRT) or any phage therapy within 1 year of randomization. Receipt of bezlotoxumab within 3 months of randomization.
   11. Participants treated with another antimicrobial agent directed at the current episode of CDI (metronidazole, fidaxomicin, rifaximin, tigecycline, or oral vancomycin) for >24 hours of treatment within the 3 days prior to randomization will not be eligible for enrollment.
2. Pregnant or breastfeeding women.
3. Receipt of any investigational medication during the last month (30 days or 5 half lives, whichever is longer) prior to randomization.
4. Active and uncontrolled HIV with CD4 <200/mm3.
5. Presence of active malignancy undergoing chemotherapy that is expected to cause significant immunosuppression, hematologic malignancy undergoing induction chemotherapy, or recent bone marrow or solid organ transplant (within 1 month prior to randomization) undergoing treatment with medications for the rejection of transplantation. In the investigator's opinion, is expected not to survive through the duration of the study (approximately 70 days) due to complications of the malignancy, or in the investigator's opinion will require oral or intravenous systemic antibiotic therapy during the study for malignancy related conditions.
6. Severe neutropenia defined as ANC <500 cells/mm3
7. Severe hepatic impairment at screening including clinical signs of cirrhosis, end-stage hepatic disease (eg, ascites, hepatic encephalopathy), or Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) ≥ 3x upper limit of normal (ULN) or total bilirubin ≥ 2x ULN.
8. Any other surgical or medical condition (including a clinically significant laboratory abnormality) as determined by the investigator or the medical monitor, that could interfere with the participant's ability to participate in the study, the administration of study treatment, and/or the interpretation of study results that, in the investigator's opinion, may confound study assessments or study procedures.
9. Known hypersensitivity to CRS3123 or oral vancomycin.
10. An employee of the investigator or study center with direct involvement in the proposed study or other studies under the direction of that investigator or study center, as well as a family member of the employee or the investigator.
11. Unwillingness to stop consuming non-dietary probiotics from randomization to Day 70.
12. Participants currently taking digoxin within 1 week of screening.
13. Unwillingness to refrain from consumption of grapefruit and its juices as well as nutraceutical supplements containing curcumin from randomization until 24 hours after EOT.
14. Unwillingness to stop use of anti-diarrheals from randomization to Day 70.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Quadruple

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: CRS3123 200 milligram; CRS3123 200 milligram dose (400 mg/day) given orally at approximately 6-hour intervals for 10 days. Due to the difference in dosing schedules between CRS3123 (twice a day) and the standard of care vancomycin (four times a day) and appearance of study drugs used in the 3 Arms, placebo will be used to match the total number of capsules in each arm.	Drug: CRS3123; Study drug dosed PO BID for a total of 10 days
Experimental: CRS3123 400 milligram; CRS3123 400 milligram dose (800 mg/day) given orally at approximately 6-hour intervals for 10 days. Due to the difference in dosing schedules between CRS3123 (twice a day) and the standard of care vancomycin (four times a day) and appearance of study drugs used in the 3 Arms, placebo will be used to match the total number of capsules in each arm.	Drug: CRS3123; Study drug dosed PO BID for a total of 10 days
Active Comparator: Vancomycin 125 milligram; Vancomycin 125 milligram dose (500 mg/day) given orally at approximately 6-hour intervals for 10 days.	Drug: Active Comparator; Active comparator dosed PO QID for 10 days

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Rate of Clinical Cure at the Test of Cure [TOC] Visit in the Intent-to-treat [ITT] Population	Clinical cure is defined as survival through TOC/Day 12 and resolution of diarrhea (i.e., <3 unformed bowel movements [UBM] [Bristol Stool Scale score of 5, 6, or 7] at end-of-treatment (EOT)/Day 10 with maintenance of resolution through TOC/Day 12 and no further requirement for treatment of CDI through TOC/Day 12. Numbers reported below indicate participants from each cohort that were clinical cures, clinical failures, or indeterminate at the TOC/Day 12 visit.	TOC/Day 12

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Rate of Clinical Cure at Test of Cure (TOC) in the Microbiological-ITT (mITT) Population	Clinical cure is defined as survival through TOC/Day 12 and resolution of diarrhea (i.e., <3 unformed bowel movements [UBM] [Bristol Stool Scale score of 5, 6, or 7] at end-of-treatment (EOT)/Day 10 with maintenance of resolution through TOC/Day 12 and no further requirement for treatment of CDI through TOC/Day 12. Numbers reported below indicate participants from each cohort that were clinical cures, clinical failures, or indeterminate at the TOC/Day12 visit.	TOC/Day 12
Rate of Clinical Cure at Test of Cure (TOC) in the Per Protocol (PP) and Microbiologically Evaluable (ME) Populations	Clinical cure is defined as survival through TOC/Day 12 and resolution of diarrhea (i.e., <3 unformed bowel movements [UBM] [Bristol Stool Scale score of 5, 6, or 7] at end-of-treatment (EOT)/Day 10 with maintenance of resolution through TOC/Day 12 and no further requirement for treatment of CDI through TOC/Day 12. Numbers reported below indicate participants from each cohort that were clinical cures, clinical failures, or indeterminate at the TOC/Day12 visit.	TOC/Day 12
Rate of Total Relief of Symptoms of Clostridioides Difficile Infection at Test of Cure (TOC) in the Microbiological-ITT (mITT) Population	Total relief of symptoms at TOC/Day 12 is defined as resolution (< 3 per day) of unformed bowel movements, an investigator's assessment of clinical cure, and the resolution of signs or symptoms of CDI recorded at baseline. Numbers reported below indicate participants from each cohort that had total relief of symptoms at TOC/Day 12 and those that did not.	TOC/Day 12
Rate of Total Relief of Symptoms of Clostridioides Difficile Infection at Test of Cure (TOC) in the Per Protocol (PP) and Microbiologically Evaluable (ME) Populations	Total relief of symptoms at TOC/Day 12 is defined as resolution (< 3 per day) of unformed bowel movements, an investigator's assessment of clinical cure, and the resolution of signs or symptoms of CDI recorded at baseline. Numbers reported below indicate participants from each cohort that had total relief of symptoms at TOC/Day 12 and those that did not.	TOC/Day 12
Time to Resolution of Diarrhea Through Test of Cure (TOC) in the Microbiological-ITT (mITT) Population	The time to resolution of diarrhea is defined as the time elapsed from the first dose of study treatment to the last unformed bowel movement before 2 consecutive days of < 3 unformed bowel movements (Bristol Stool Scale score of 5, 6, or 7) per day through TOC/Day 12. Values reported below are median days to resolution for each cohort.	Study Day 1 until the date of documented resolution, assessed up to TOC/Day 12
Time to Resolution of Diarrhea Through Test of Cure (TOC) in the Per Protocol (PP) and Microbiologically Evaluable (ME) Populations	The time to resolution of diarrhea is defined as the time elapsed from the first dose of study treatment to the last unformed bowel movement before 2 consecutive days of < 3 unformed bowel movements (Bristol Stool Scale score of 5, 6, or 7) per day through TOC/Day 12. Values reported below are median days to resolution for each cohort.	Study Day 1 until the date of documented resolution, assessed up to TOC/Day 12
Rate of Early Recurrence of Clostridioides Difficile Infection Through Day 40 in the Microbiological-ITT (mITT) Population	Rate of early recurrence of C. difficile infection (CDI) is defined as a new episode of diarrhea (≥ 3 unformed bowel movements [Bristol Stool Scale score of 5, 6, or 7] in a 24-hour period) with a positive toxin result and requires retreatment for CDI before Day 40. The table below shows the number of participants per cohort that experienced a recurrence before Day 40 and those that did not. Only participants that were clinical cures at TOC/Day 12 were included in the analysis.	Post TOC/Day 12 visit through Day 40
Rate of Early Recurrence of Clostridioides Difficile Infection Through Day 40 in the Microbiologically Evaluable (ME) Population	Rate of early recurrence of C. difficile infection (CDI) is defined as a new episode of diarrhea (≥ 3 unformed bowel movements [Bristol Stool Scale score of 5, 6, or 7] in a 24-hour period) with a positive toxin result and requires retreatment for CDI before Day 40. The table below shows the number of participants per cohort that experienced a recurrence before Day 40 and those that did not. Only participants that were clinical cures at TOC/Day 12 were included in the analysis.	Post TOC/Day 12 visit through Day 40
Rate of Late Recurrence of Clostridioides Difficile Infection (Between Day 40 and Day 70) in the Microbiological-ITT (mITT) Population	Rate of late recurrence of CDI is defined as a new episode of diarrhea (≥ 3 unformed bowel movements [Bristol Stool Scale score of 5, 6, or 7] in a 24-hour period), with a positive toxin result and requires retreatment of CDI between Day 40 and Day 70. The table below shows the number of participants per cohort that experienced a recurrence between Day 40 and Day 70 and those that did not. Analysis populations for this assessment only includes participants that had an investigator assessment of clinical cure at TOC/Day 12. Participants that were indeterminate at TOC/Day 12 or recurrent prior to Day 40 were excluded.	Day 40 - Day 70
Rate of Late Recurrence of Clostridioides Difficile Infection (Between Day 40 and Day 70) in the Microbiologically Evaluable (ME) Population	Rate of late recurrence of CDI is defined as a new episode of diarrhea (≥ 3 unformed bowel movements [Bristol Stool Scale score of 5, 6, or 7] in a 24-hour period), with a positive toxin result and requires retreatment of CDI between Day 40 and Day 70. The table below shows the number of participants per cohort that experienced a recurrence between Day 40 and Day 70 and those that did not. Analysis populations for this assessment only includes participants that had an investigator assessment of clinical cure at TOC/Day 12. Participants that were indeterminate at TOC/Day 12 or recurrent prior to Day 40 were excluded.	Day 40 - Day 70
Rate of Recurrence of Clostridioides Difficile Infection Through Day 70 in the Microbiological-ITT (mITT) Population	Rate of recurrence of CDI is defined as a new episode of diarrhea (≥3 unformed bowel movements [Bristol Stool Scale score of 5, 6, or 7] in a 24-hour period) with a positive toxin result and requires retreatment for CDI at any point between TOC/Day 12 and Day 70. The table below shows the number of participants per cohort that experienced a recurrence between TOC/Day 12 and Day 70 and those that did not. Analysis populations for this assessment only includes participants that had an investigator assessment of clinical cure at TOC/Day 12.	Post TOC/Day 12 visit through Day 70
Rate of Recurrence of Clostridioides Difficile Infection Through Day 70 in the Microbiologic Evaluable (ME) Population	Rate of recurrence of CDI is defined as a new episode of diarrhea (≥3 unformed bowel movements [Bristol Stool Scale score of 5, 6, or 7] in a 24-hour period) with a positive toxin result and requires retreatment for CDI at any point between TOC/Day 12 and Day 70. The table below shows the number of participants per cohort that experienced a recurrence between TOC/Day 12 and Day 70 and those that did not. Analysis populations for this assessment only includes participants that had an investigator assessment of clinical cure at TOC/Day 12.	Post TOC/Day 12 visit through Day 70
Rate of Global Cure in the Microbiological-ITT (mITT) Population	Global cure is defined as a clinical cure at TOC/Day 12 without recurrence through Day 40. The table below shows the number of participants per cohort that experienced a recurrence between TOC/Day 12 and Day 40 and those that did not.	Post TOC/Day 12 visit through Day 40
Rate of Global Cure in the Per Protocol (PP) and Microbiologically Evaluable (ME) Populations	Global cure is defined as a clinical cure at TOC/Day 12 without recurrence through Day 40. The table below shows the number of participants per cohort that experienced a recurrence between TOC/Day 12 and Day 40 and those that did not.	Post TOC/Day 12 visit through Day 40

Other Outcome Measures

Outcome Measure	Time Frame
To assess the effect of CRS3123 on the microbiology, fecal microbiome, and fecal biomarkers of inflammation, to assess microbiological effect, and to evaluate metabolomics	Screening through Day 70
To assess the fecal concentrations of CRS3123 in the CRS3123 200 mg and 400 mg dose groups	Screening through Day 10 (EOT)

Collaborators and Investigators

• Sponsor: Crestone, Inc
• Collaborators: National Institute of Allergy and Infectious Diseases (NIAID)
• Investigators: Principal Investigator: Urs Ochsner, PhD, Crestone, Inc

Publications and helpful links

General Publications

• Louie T, Ribble W, Boccumini L, Johnson K, De Groote MA, Day J, Mason C, Sun X, Freeman J, Gu K, Tillotson G, Wilcox MH, Janjic N, Jarvis TC, Nayak SU, Ochsner UA, Bruss JB. Safety and efficacy of CRS3123 in adults with a primary episode or first recurrence of Clostridioides difficile infection: a phase 2, randomised, double-blind, multicentre, vancomycin-controlled study. Lancet Infect Dis. 2026 Jan 22:S1473-3099(25)00721-2. doi: 10.1016/S1473-3099(25)00721-2. Online ahead of print.

Study record dates

Study Major Dates

• Study Start (Actual): January 5, 2021
• Primary Completion (Actual): April 16, 2024
• Study Completion (Actual): April 16, 2024

Study Registration Dates

• First Submitted: January 19, 2021
• First Submitted That Met QC Criteria: March 1, 2021
• First Posted (Actual): March 4, 2021

Study Record Updates

• Last Update Posted (Actual): March 27, 2026
• Last Update Submitted That Met QC Criteria: March 13, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Keywords: CDI; Cdiff Infection; Clostridiodes difficile infection; Cdiff
• Additional Relevant MeSH Terms: Infections; Gram-Positive Bacterial Infections; Bacterial Infections; Bacterial Infections and Mycoses; Clostridium Infections; Anti-Bacterial Agents; Anti-Infective Agents; REP 3123
• Other Study ID Numbers: 19-0021; 75N93019C00056 (Other Grant/Funding Number: NIAID)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No