Use of Fidaxomicin Compared to Vancomycin for Decolonization of C. Difficile in Patients With Inflammatory Bowel Disease

This is a randomized, double-blind study to assess the safety and efficacy of fidaxomicin compared to vancomycin for decolonization of C. difficile in IBD patients. A total of 60 patients who meet eligibility criteria will be randomized 1:1 to either the fidaxomicin or vancomycin arm. The vancomycin arm will receive a dose of 125 mg PO q 6 hours for 10 days. The fidaxomicin arm will receive 200 mg PO BID for 10 days. In order to ensure blinding, both antibiotics will be concealed in opaque 00 capsule shells. In addition, those in the fidaxomicin arm will receive 2 placebo capsules so that all participants will receive 4 capsules daily for 10 days. Microbiome assessment and C. difficile testing will be performed at baseline, day 5, day 10, and weeks 4, 8, and 26.

Study Overview

• Status: Not yet recruiting
• Conditions: Inflammatory Bowel Disease (IBD); Clostridioides Difficile Infection
• Intervention / Treatment: Drug: Vancomycin (POC); Drug: Fidaxomicin

Detailed Description

This randomized, double-blind trial will assess the ability of fidaxomicin compared to vancomycin to decolonize C. difficile in the IBD patient population.

Participants who meet eligibility criteria will be randomized 1:1 to either vancomycin or fidaxomicin treatment. The vancomycin arm will receive a dose of 125 mg PO q 6 hours for 10 days. The fidaxomicin arm will receive 200 mg PO BID for 10 days. In order to ensure blinding both antibiotics will be concealed in opaque 00 capsule shells. In addition, those in the fidaxomicin arm will receive 2 placebo capsules so that all participants will receive 4 capsules daily for 10 days. Participants will end dosing after 10 days, but monitoring will continue to week 8. Both participants and study team will be blinded to treatment arm allocation.

Participants will be assessed through week 8 for the primary outcome, decolonization. Safety and tolerability outcomes will be assessed through week 8. In addition, secondary efficacy outcomes including IBD disease activity and development of CDI will be evaluated at week 8 and week 26. Participants will also be followed through week 26 for long-term safety, efficacy, and clinical outcomes. Disease activity and symptoms will be recorded from time of informed consent through to the week 26 trial visit. Stool samples for biomarker assessments and C. difficile testing will be collected at scheduled trial visits per Schedule of Assessments.

The primary outcome, decolonization of C. Difficile at week 8, will be confirmed via stool sampling. Additional C. difficile testing will be done at week 26.

Participants that experience intolerable adverse events will be withdrawn from the study and will be considered treatment failures. Additional subjects may be enrolled to obtain 60 patients with week 8 data.

The study will enroll approximately 60 adult participants at a single center.

• Study Type: Interventional
• Enrollment (Estimated): 60
• Phase: Phase 4

Contacts and Locations

• Study Contact: Name: Alexander Carlin; Phone Number: 6175257322; Email: acarlin@bwh.harvard.edu
• Study Contact Backup: Name: Jessica Allegretti, MD, MPH; Phone Number: 6177326389; Email: jallegretti@bwh.harvard.edu

Study Locations

• United States
  • Massachusetts
    • Boston, Massachusetts, United States, 02115
      • Brigham and Women's Hospital
      • Contact: Alexander Carlin; Phone Number: 6175257322; Email: acarlin@bwh.harvard.edu

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

1. Signed informed consent.
2. Male or female > 18 years of age.
3. IBD diagnosis (CD, UC or indeterminant Colitis will be permitted.)
4. Presenting for outpatient colonoscopy for any indication.

Exclusion Criteria:

1. Unable to provide consent.
2. Patients with previous colectomy, ostomy, J-pouch, or previous colon surgery (excluding appendectomy.)
3. Unable to complete study procedures.
4. Chronic use of antibiotics.
5. Inability or unwillingness to swallow capsules.
6. Allergy or sensitivity to vancomycin, fidaxomicin, or microcrystalline cellulose.

Study Plan

How is the study designed?

Design Details

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

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Vancomycin; Vancomycin is glycopeptide antibiotic that has broad gram-positive coverage. The current approved dose is 125mg PO every 6 hours for 10 days. Appropriate dosing and tolerance of vancomycin is well defined in both healthy and hospitalized populations, as it is already approved and indicated by the FDA for use in treating C. difficile infection.	Drug: Vancomycin (POC); Vancomycin is glycopeptide antibiotic that has broad gram-positive coverage. Patients will receive 125mg PO every 6 hours for 10 days.
Active Comparator: Fidaxomicin; Fidaxomicin is a macrolide antibiotic. It is narrow spectrum with potent bactericidal activity specifically against C. difficile. The approved dose is 200mg PO twice daily for 10 days. Appropriate dosing and tolerance of fidaxomicin is well defined in both healthy and hospitalized populations, as it is already approved and indicated by the FDA for use in treating C. difficile infection.	Drug: Fidaxomicin; Fidaxomicin is a macrolide antibiotic. It is narrow spectrum with potent bactericidal activity specifically against C. difficile. Patients will receive 200mg PO twice daily for 10 days.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
C. difficile decolonization	Absence of C. difficile via PCR in Week 8 stool sample	8 weeks
Safety and tolerability	Subject incidence of treatment-emergent adverse events (including treatment-emergent adverse events for clinically significant changes in laboratory parameters and vital signs)	8 weeks

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Biomass of C. difficile	Change in stool C. difficile biomass in patients at week 8 by quantitative culture and qPCR	8 weeks
C. difficile infection surveillance	Incidence of patients developing CDI through Week 26	26 weeks
Long-term effect of C. difficile decolonization on IBD clinical outcomes	Change in IBD clinical scores from baseline at week 8 and week 26. IBD clinical scores are used to assess IBD patient symptoms. The assessments are separated between scores for Ulcerative Colitis (UC) and Crohn's Disease (CD). The Harvey Bradshaw Index (HBI) is a clinical assessment for IBD patients with Crohn's disease while Partial Mayo Score is a clinical assessment for Ulcerative Colitis. The scores will be collected at study visit in form of a survey. The HBI score can vary but a score above 8 or 9 is considered severe disease activity. The Partial Mayo Score can range from 0 to 9 and a score above 7 is considered severe disease activity. A decrease in score from baseline to follow-up timepoints is indicative of improved IBD patient symptoms. A decrease in score from baseline to follow-up timepoints is indicative of improved IBD patient symptoms.	26 weeks

Collaborators and Investigators

• Sponsor: Brigham and Women's Hospital
• Investigators: Principal Investigator: Jessica Allegretti, MD, MPH, Brigham and Women's Hospital

Study record dates

Study Major Dates

• Study Start (Estimated): September 1, 2026
• Primary Completion (Estimated): September 1, 2030
• Study Completion (Estimated): September 1, 2031

Study Registration Dates

• First Submitted: January 21, 2025
• First Submitted That Met QC Criteria: January 21, 2025
• First Posted (Actual): January 27, 2025

Study Record Updates

• Last Update Posted (Estimated): November 3, 2025
• Last Update Submitted That Met QC Criteria: October 31, 2025
• Last Verified: October 1, 2025

More Information

Terms related to this study

• Keywords: Ulcerative Colitis; Crohn's Disease; C. difficile
• Additional Relevant MeSH Terms: Intestinal Diseases; Infections; Digestive System Diseases; Gastrointestinal Diseases; Colonic Diseases; Gastroenteritis; Gram-Positive Bacterial Infections; Bacterial Infections; Bacterial Infections and Mycoses; Colitis; Colitis, Ulcerative; Clostridium Infections; Inflammatory Bowel Diseases; Peptides; Amino Acids, Peptides, and Proteins; Organic Chemicals; Carbohydrates; Polycyclic Compounds; Macrolides; Lactones; Glycoconjugates; Macrocyclic Compounds; Glycopeptides; Polyketides; Fidaxomicin; Vancomycin
• Other Study ID Numbers: 2025P000187

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
• product manufactured in and exported from the U.S.: Yes