Due to the nature of Clostridium difficile infections, particularly the high rate of recurrence following standard treatments, participating in a clinical trial may be an option for sufferers who don’t respond to antibiotics. Some clinical trials focus on developing vaccines and other preventatives. Those trials often need healthy volunteers who haven’t had a CDI to participate. The following are large, active trials focused on C. diff treatment and prevention. For smaller scale and local trials, please visit our In Your State page and search for ones near you.

What is a Clinical Trial?

A clinical trial is a research study that using human volunteers that is intended to add to medical knowledge. Clinical trials can vary in size from a single location in one country to multiple locations in multiple countries. Some research studies may determine if an investigational product can be administered to children or special populations. Some studies assess a drug’s long-term effectiveness and its impact on the quality of a person’s life.

All studies of a drug, biological product, or medical device regulated by FDA must be reviewed, approved, and monitored by an institutional review board (IRB) or Ethics Committee (EC). All clinical trials are conducted using Principles of Good Clinical Practice (GCP) and are under the supervision of an IRB or EC whose mission is to ensure the safety and welfare of study participants. To learn more about clinical trials, please visit Clinical Trials.gov.


Artugen Therapeutics

Artugen is developing a novel oral Live Biotherapeutic Product for the prevention of C. difficile infection recurrence. The investigational drug, ART24 capsules, is composed of freeze-dried gut-derived bacteria called Bacillus amyloliquefaciens which acts directly against the C. difficile bacteria. ART24-1-001 is a blinded study for people with a recent C. difficile infection (first episode or recurrent infection). The study is to see how well ART24 is tolerated and how well ART24 can help prevent future episodes of C. difficile infection compared with placebo.

You may be eligible to participate in ART24-1-001 if you meet these criteria*:

  • 18-75 years old
  • Currently taking or have recently finished (within the last 6 days) taking antibiotics for a C. difficile infection
  • Do not have inflammatory bowel disease (IBD)

*Other criteria will also apply.

All eligible participants will receive:

  • ART24 or placebo
  • Study-related medication and exams at no cost
  • Compensation for reasonable travel and meal expenses

This study is currently recruiting in the following areas: Riverton (UT), Hillsborough (NJ), Bronx (NY), Doral (FL), La Mesa/Chula Vista (CA), Shreveport (LA), Massapequa (NY/Long Island) and Boston (MA).

To learn more or join the study please contact: clinicaltrials@artugentherapeutics.com.

Finch Therapeutics

The PRISM-EXT study is for individuals fighting recurrent C. diff.  PRISM-EXT is an open-label study of investigational capsules designed to break the cycles of infection by delivering a whole community of beneficial bacteria to the areas of the intestine affected by C. diff. If you are eligible, you would receive these investigational capsules (there is no placebo group).

You may be eligible to participate in PRISM-EXT if you meet these criteria*:

  • 18 years or older
  • Have had a C. diff infection more than once
  • Currently taking antibiotics for a C. diff infection, or will soon start taking antibiotics for a C. diff infection
  • Do not have inflammatory bowel disease (IBD)

*Other criteria will also apply.

All eligible participants will receive:

  • CP101 (active study drug)
  • Dedicated, experienced medical care
  • Free transportation and coverage of all study-related costs

Click here to learn more about PRISM-EXT and see if there is a study site near you.


Prolacta Bioscience is a company dedicated to Advancing the Science of Human Milk. It has recently developed a pharmaceutical consisting of beneficial components derived from human milk and is investigating its usefulness in the treatment of C. difficile associated diarrhea.

In a healthy individual, the bacteria population living in the gut (microbiome) provides many health benefits and can prevent pathogens from causing infections. Antibiotics wipe out the beneficial bacteria in the gut and can allow the harmful bacteria, C. difficile to overgrow. C. difficile causes disease by producing toxins that injure the cells of the gut wall. Although some specific antibiotics can cure C. difficile infections, at times the pathogen can resist antibiotics by forming spores. These C. difficile spores are immune to the effects of antibiotics and, under certain conditions, can become harmful active bacteria which start the disease cycle all over again. If the gut Microbiome does not return to a healthy state, the C. difficile infection will continue to recur (come back) after each antibiotic treatment. Prolacta’s new product has natural biological activities that could help restore the individual’s healthy gut Microbiome and support immune functions to decrease relapses of C. difficile disease, without having to introduce a new bacterial population collected from outside sources.

Study Product: liquid product (consisting of human milk-derived components) or placebo, administered orally three times daily for seven days.

Study Phase: I

Study Design: double-blind, randomized, placebo-controlled dose escalation trial. Study subjects will receive one of three doses depending upon which dose group is recruiting at the time of their participation.

Population: individuals age 18 or older who have had no more than four prior occurrences of C. difficile associated diarrhea and are currently being treated with standard of care antibiotics. The target enrollment number is between 48 and 54.

Status: Currently Recruiting

Locations: This study is currently being conducted in the following areas: Idaho Falls, ID, Billings, MT, Omaha, NE, Orlando, FL, Miami-Dade, FL, New York, NY and Ventura, CA.

For further information contact: (888) 776-5228  info@prolacta.com

Rebiotix Inc.

The PUNCH CD 3 study is a Phase 3 clinical study to evaluate the safety and efficacy of Rebiotix RBX2660 for the prevention of recurrent Clostridium difficile infection (CDI).

This prospective, randomized, double-blinded, placebo-controlled clinical research study is expected to enroll up to 270 patients at 60 research sites in the U.S. and Canada. Patients that meet the study requirements and choose to enroll will be randomized to received either RBX2660, an investigational new drug, or a placebo. Two out of every three study patients will receive RBX2660, and one out of every three study patients will receive the placebo study treatment (2:1 randomization). Study patients whose CDI returns within 8 weeks after blinded study treatment may be scheduled to receive an RBX2660 treatment (no placebo). The study’s primary endpoint will compare the proportion of patients with treatment success following treatment with RBX2660 to prevent recurrent CDI within 8 weeks of blinded treatment as compared to placebo.

To learn more or join the study, visit the ClinicalTrials.gov

Seres Therapeutics

Most Clostridioides difficile (C. diff) infections occur after antibiotic treatment. Why? Our gut contains trillions of microbes, called the microbiome, which protect us from bacterial invaders that can cause disease. Antibiotics disrupt the microbiome by killing both good and bad bacteria. When the microbiome is damaged, bad bacteria, like C diff, can take advantage and cause disease. Although specific antibiotics can kill the active C diff bacteria, the inactive forms (i.e. C diff spores) are untouched. When the microbiome is disrupted, these spores turn into active C diff bacteria and cause disease again and again – usually after antibiotic treatment has finished.

Seres Therapeutics is developing an investigational microbiome drug called SER-109. This medicine is being developed to prevent C diff from coming back by repairing the microbiome. Seres is pleased to announce the positive top line results from its ECOSPOR-III trial reported in August 2020. In a placebo-controlled randomized trial of 182 patients with multiply (> 3) recurrent C. diff infection, the recurrence rate was significantly reduced from 41.3% in placebo recipients to 11.1% in the SER-109 recipients. In addition, SER-109 was well tolerated. Based on these encouraging results, Seres is now enrolling an open-label study, in which all participants will receive SER-109. This new study will be open to patients experiencing their first recurrence or multiple recurrences of C. diff at sites in the US and Canada. To find a site near you, please click on the following link (https://www.serescdiffstudy.com/)

To learn more about Seres Therapeutics and Clinical Trials in Progress please click on the following link to learn more.

Summit Therapeutics

Ridinilazole is being developed by Summit Therapeutics as a potential treatment for C. difficile infection (CDI). It’s a new antibiotic, and Summit is testing whether it can improve patient outcomes over the current standard of care, vancomycin, in two global clinical trials. In an earlier clinical trial in patients with CDI, ridinilazole was found to be superior to vancomycin in a measure called sustained clinical response, which tested if patients were cured after treatment and did not experience a recurrence within 30-days post-treatment. More information on ridinilazole can be found by visiting www.summitplc.com/our-programmes/c-difficile-infection.

Some key information about the trials:

  • Each trial is expected to enroll up to 680 patients
  • Patients will be randomized to receive either ridinilazole or vancomycin, and neither the patients nor the study doctors will know which drug they receive
  • Participation will involve about 7 study visits over approximately 100 days to track the safety and effectiveness of each drug
  • Patients who participate may be reimbursed for travel expenses associated with study site visits
  • Patients must be 18 years of age or older
  • Patients must have signs and symptoms of CDI, including diarrhea, in the 24 hours prior to entry in the trial and a positive toxin test on a stool sample produced within 72 hours of entry into the trial
  • Patients cannot have had more than one prior episode of CDI in the previous three months or more than three episodes in the past 12 months
  • Patients cannot have had more than 24 hours of CDI antibiotic treatment prior to entry into the trial
  • There are additional entry criteria and considerations; the study doctors will ultimately decide whether a patient is eligible for entry into the clinical trials and the patient will be required to give consent

To see if you’re eligible to participate please visit the study enrollment site at Clara Health.

Vedanta Biosciences

Vedanta Biosciences, Inc. is dedicated to finding treatments for patients with serious infections and immune diseases. VE303 is Vedanta’s investigational treatment for patients with recurrent C. difficile infections (CDI).  VE303 is a preparation of eight different types of bacteria grown in clean conditions, dried, powdered and put into capsules to be administered orally.  The bacteria are reactivated once they reach the intestines. The 8 bacteria were selected for their ability to provide resistance against C. difficile.   In contrast to fecal transplants, which rely on direct sourcing of fecal donor material of inconsistent composition, VE303 is manufactured from pure cell banks that yield a product of uniform composition, free of viruses and uncharacterized bacteria.

The results of Phase 1 study of VE303 in healthy volunteers showed both rapid expansion of protective VE303 bacteria in the gut and accelerated recovery to a healthy microbiome after disruption to the normal microbiome in the gut caused by antibiotics. Based on these positive Phase 1 results, Vedanta is now evaluating VE303 in a Phase 2 clinical study (CONSORTIUM) in participants with recurrent CDI to see if it can prevent future CDI recurrences by restoring the intestinal bacteria to a healthy state.

Up to 146 participants over the age of 18 years old with any number of recurrent CDI episodes including the current episode will be enrolled in the CONSORTIUM study. Two out of every three study patients will receive VE303, and one out of every three study participants will receive the placebo study treatment (2:1 randomization) upon completion of standard antibiotic treatment. CONSORTIUM’s primary study objective will be to determine the safety and efficacy of VE303 at preventing CDI recurrence within 8 weeks of completion of antibiotic treatment.

CONSORTIUM is currently recruiting participants across North America (U.S. and Canada). If you or someone close to you has been diagnosed with recurrent CDI, you may be eligible to take part in the study. To learn more about the study and to locate a study site near you, please visit: https://www.clinicaltrials.gov/ct2/show/NCT03788434

If you are interested in study participation, please visit The Consortium Study recruitment page.

National Institute of Allergy and Infectious Diseases (NIAID) 

National Institute of Allergy and Infectious Diseases (NIAID) is conducting a multi-center, randomized, placebo controlled, partially blinded trial comparing the safety and efficacy of fecal microbiota transplantation versus placebo both delivered by rectal enema in subjects 18 years of age or older with recurrent Clostridium difficile Associated Disease (CDAD). 162 male or female subjects will be enrolled in the study. Enrolled subjects will be randomized at each site to receive either FMT by enema or placebo by enema in a 2:1 ratio. Study duration is 4 years, subject participation duration is approximately 3 years. Primary study objectives are to: 1) evaluate the safety of FMT(s) delivered by enema vs. placebo delivered by enema, 2) determine efficacy of FMT delivered by enema vs. placebo delivered by enema.

For more information, please follow this link to ClinicalTrials.gov

Vaccine & Preventatives

Da Volterra

The Da Volterra clinical study is for hospitalized patients requiring a systemic antibiotic treatment for a proven or strongly suspected bacterial infection who have a history of Clostridium difficile infection (CDI or C. diff) or are over 65 years of age. The study is evaluating the safety and effectiveness of the study drug DAV132 to prevent the emergence of antibiotic-resistance infections compared to a placebo. This clinical study is for patients in Bulgaria, Germany, Romania and Serbia.

The study drug, DAV132, is a novel therapeutic option for preserving the intestinal microbiota. This may aid in preserving the diverse community of bacteria found in the healthy human gut, which may prevent the emergence or reoccurrence of a Clostridium difficile infection (CDI). DAV132 is encapsulated for oral administration.

DAV132 is regulated as a medical device in Europe and as a drug in the United States of America. DAV132 is considered “investigational” because it has not been approved by the US Food and Drug Administration for treating CDI.

Click here to learn more about DAV132 and see if there is a study near you and if you are eligible.

Pfizer’s CLOVER Trial

The purpose of the Clover Trial is to evaluate the safety and efficacy of an investigational vaccine in reducing the chances of getting sick due to C. diff. The knowledge gained from this study may help others in the future. Participation in this study is expected to last between 18 and 42 months and will require 5 office visits within the first 7 months. You will also receive periodic contact from the study team, including regular electronic reminders of your participation and routine telephone calls after 12 months and at the end of the study. Approximately 16,000 patients are expected to participate in the study globally. To learn more and see if you qualify, click here.