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.



Crestone is developing a novel antibiotic known as CRS3123 for treatment of C. difficile infection, or CDI. In preclinical (early) studies CRS3123 has demonstrated that it quickly halts production of C. difficile toxin and spores via a new mechanism of action. In Phase 1 human clinical trials it caused minimal disruption of other, normal gut bacteria. In this Phase 2 study sponsored by NIAID (NIH), Crestone will test two different doses of CRS3123 compared to a standard antibiotic treatment for this infection called vancomycin.

If enrolled, subjects will receive either, 400 mg or 800 mg of CRS3123 or vancomycin for 10 days. Doses will be taken by mouth, every 6 hours. Neither subjects nor study healthcare providers will know which drug is being administered. Then subjects will be followed for an additional 60 days, resulting in about eight outpatient study visits over 70 days. Participants will receive study-related medication and exams at no cost and may be reimbursed for travel expenses for study visits.

The study will enroll subjects 18 or older who have a primary episode or first recurrence of CDI, including diarrhea in the last 24 hours and a positive C. difficile toxin test on a stool sample. They may not participate if they have had more than one CDI episode in the last three months (or one that was not initially responsive to vancomycin), or two CDI episodes in the past twelve months. Pregnant or breastfeeding women may not participate in this study, and other entry criteria apply. Study physicians will determine eligibility and then request subjects’ consent to participate.

This study is currently recruiting in the following areas: Sacramento, CA; Lancaster, CA; Calgary, AB CANADA; London, ON CANADA; St. Petersburg, FL; Miami Lakes, FL; Pompano Beach, FL; Miami, FL; Doral, FL; Idaho Falls, ID; Shreveport, LA; Rochester, MN; Omaha, NE; Mentor, OH; Toledo, OH; Uniontown, PA; Union City, TN; San Antonio, TX; Cedar Park, TX; Houston, TX; Seattle, WA.

To learn more, please visit Crestone’s website CRESTONE C-DIFF Study or to join the study please contact Vicki J Abbas, BSN RN at vabbas@crestonepharma.com or by phone at 303-263-4646.



Deinove has developed an intravenous (IV) antibiotic that may help people with a C. difficile infection (CDI). The 001C16 study is an open-label study to see how well the study drug, DNV3837, is tolerated and how it works against CDI when compared to standard of care treatment. Open label means that no placebos are used and qualifying participants will receive DNV3837. Qualifying participants will receive DNV3837 via IV for 6 hours once daily for 10 consecutive days.

You may be eligible to participate in the 001C16 study if you meet the following criteria*

  • 18 years of age or older
  • A diagnosis of non-severe or severe CDI
  • You have taken no more than 24 hours of medication for your current CDI prior to screening

*Other criteria will also apply

All eligible participants will receive:

  • DNV3837 (study drug)
  • Study related exams and treatment at no cost

To learn more or to find a participating clinic near you, visit http://bit.ly/cdiffstudy.


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

Study website: https://prism4trial.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

Seres has now completed enrolling patients with first or subsequent recurrence of C. diff infection in the open-label ECOSPOR IV clinical study. Currently, there are no clinical trials enrolling patients for SER-109.

A Phase 3 trial, reported in August 2020, met its primary endpoint and showed that SER-109 significantly decreased the chance of a recurrence of C. diff in patients who’d had multiple recurrences. Approximately 88% of patients who received SER-109 did not experience a recurrence, compared to approximately 60% of patients who received placebo.

As part of its sustained commitment to patients, Seres may be able to provide access to  its investigational drug, SER-109, under certain limited conditions, through its Expanded Access Program (EAP). Seres’ main objective when initiating an EAP is to equitably serve the patient community with compassion and dignity. Seres aims to accomplish this by thoughtfully balancing requests for treatment with the need to protect patient safety and ensure ethical and compliant access to medications.

It is important to remember that investigational products have not been approved or cleared by regulatory bodies like the FDA for their specific use. Doctors and patients should consider all possible benefits and risks when seeking expanded access to an investigational product.

Seres will consider granting expanded access to this investigational drug only if the following criteria are met (along with other defined eligibility parameters for disease under study):

• The patient has a serious or life-threatening illness with no comparable or satisfactory alternative therapies; the patient is no longer responsive to, or able to tolerate, available therapies; or the patient has a relevant medical condition, that in the opinion of the physician, makes an approved agent unsuitable for the patient.

• The patient is ineligible for, or otherwise unable to, participate in a clinical trial.

• The patient has a disease for which there is sufficient evidence indicating that the potential benefits of expanded access outweigh the known or anticipated risks to the patient (and such risks are not unreasonable in the context of the disease or condition to be treated).

• The investigational drug is currently in clinical development – that is, it is currently being studied in humans. Providing the investigational drug for the requested use will not interfere with the initiation, conduct, or completion of clinical trials.

For information on the SER-109 Expanded Access Program, please visit https://www.serestherapeutics.com/patients-and-physicians/.

Read a C. diff Story about a survivor who participated in this clinical trial: https://peggyfoundation.org/story/debra-spencer/


Summit Therapeutics

Ridinilazole is being developed by Summit Therapeutics as a potential treatment for C. difficile infection (CDI) and is not approved by any regulatory body. It’s an investigational antibiotic being studied in adolescent patients with CDI.  The purpose of the study is to determine whether ridinilazole is safe and effective as compared to the current standard of care. In an earlier clinical trial in patients with CDI, ridinilazole was found to have higher sustained clinical response compared to vancomycin.  Sustained clinical response measured the if patients were cured after treatment and whether they experienced 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 trial:

  • This trial is expected to enroll approximately 40 adolescent patients (12 to ≤ 18 years of age)
  • Patients will be randomized to receive either ridinilazole or vancomycin, and neither the patients nor the study doctors will know which drug patients receive
  • Participation will involve about 8 study visits and/or telephone contacts 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 have signs and symptoms of CDI, require CDI treatment, and have ≥ 3 unformed bowel movements in the 24 hours prior to study randomization
  • Patients must have presence of free toxin A and/or B in stool
  • 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

For further details regarding this clinical trial please visit https://clinicaltrials.gov/ct2/show/NCT04802837 or the study website at www.ricodifycdiff.com

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.