Engineered yeast pill takes on superbug c. diff in first human trial
NCT ID NCT07649096
First seen Jun 27, 2026 · Last updated Sep 18, 2026 · Updated 10 times
Summary
This early-stage trial tests an oral capsule containing a genetically modified probiotic yeast designed to neutralize toxins produced by C. diff bacteria. The study first evaluates safety in healthy adults, then in people at risk for recurrent C. diff infection. Participants take the yeast or a placebo daily for 28 days, with close monitoring for side effects.
What this could mean
Our plain-language read of the trial. This is informational only, not medical advice or a prediction.
- Active substance
- genetically modified probiotic yeast (FZ002)
- What this could lead to
- If it works, this could point toward a new way to prevent recurrent C. diff infections without antibiotics.
- What could go wrong
- This is a very early phase 1 safety trial, so it may not show any benefit. The yeast is genetically modified, and there are unknown risks like yeast entering the bloodstream.
This is an AI summary of the original study and may miss details. Read our disclaimer.
Study facts
What this study's own registry entry says, in plain language.
- Phase
-
Phase 1
The first testing in people. Mainly checks safety and dose, usually in a small group.
- Participants
-
About 86 people
The number the study aims to enrol. It can still change while the study runs.
- Expected to start
-
Sep 2026
An estimate. Start dates often move.
- Expected to finish
-
Sep 2028
An estimate. End dates often move.
- Lead sponsor
-
A government research agency
The lead sponsor is the US National Institutes of Health.
Who can take part
This study's own entry requirements. Only the study team can say for certain whether you qualify.
- Ages
-
18 to 75 years
- Sex
-
Anyone
- Healthy volunteers
-
Accepted
You do not need to have the condition being studied to take part.
Show the full entry requirements Hide the full entry requirements
Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.
Inclusion Criteria: To be eligible to participate in Part A of this trial, an individual must meet all of the following criteria: 1. Provides written informed consent prior to the initiation of any trial procedures. 2. Is able to understand and agrees to comply with all planned trial procedures and be available for all study visits, including: 1. Receiving 28 days of blinded oral study product 2. Providing blood and self-collected stool samples 3. Is a non-pregnant individual, aged 18-75 years, inclusive, at the time of enrollment. 4. Has no more than 1 single Grade 1 screening laboratory abnormality that is not clinically significant. If the participant has more than 1 Grade 1 abnormality, it must be approved by the Division of Microbiology and Infectious Diseases \[DMID\] Medical Monitor (MM). 5. Participants of childbearing potential: use of adequate contraception for at least 4 weeks prior to enrollment and agreement to use such a method during trial participation and for an additional 4 weeks after the last dose of blinded study product. Note: Definitions of participants of childbearing potential and adequate contraception are provided in Section 13.1. 6. Agrees to refrain from ingestion of probiotics\* or fermented foods\*\* from 7 days prior to study product administration, while on blinded study product, and through Day 36 (Visit 6). \*E.g., probiotic nutritional Lactobacillus or Bifidobacterium supplements, yogurt, kefir, any "live and active culture" nutritional product, etc. \*\*E.g., kombucha, fermented pickled vegetables, etc. 7. Has good health by medical history, vital signs, physical examination, and concomitant medication review\*. Participants should be stable based on their condition over the last 3 months prior to enrollment. \*As defined by not requiring a change in therapy (including dose or frequency) or medical care for worsening disease for at least 3 months prior to enrollment. Vital signs must not meet Grade 1 or higher. 8. Not using medications daily that may affect gut motility, gastric acidity, or baseline gut function\* within 3 months of enrollment and through Day 36 (Visit 6). \*E.g., proton pump inhibitors, opioids, anti-diarrheal agents, anti-constipation agents, daily Over-the-counter \[OTC\] "heartburn" relief medications. 9. Not using glucagon-like peptide-1 (GLP-1) receptor agonists within 6 weeks of enrollment. 10. Any elective surgery (including dental) that required preoperative or postoperative antibiotics must have been completed at least 3 months prior to enrollment. 11. No history of Clostridioides difficile infection \[CDI\] (suspected or proven), no recent hospital admissions (within 3 years), and no receipt of systemic antibiotics known to increase risk of CDI\* (within 6 months). \*Systemic antibiotics that are known to increase the risk of CDI include lincosamides (e.g., clindamycin), monobactams (e.g., aztreonam), extended-spectrum penicillin combinations with beta-lactamase inhibitors (e.g., piperacillin-tazobactam), carbapenems (e.g., imipenem, meropenem, ertapenem), third generation or higher cephalosporins, and fluoroquinolones. Common oral antibiotics that would be allowable or are not known to significantly increase risk of CDI include amoxicillin, azithromycin, cephalexin, doxycycline, metronidazole, and trimethoprim/sulfamethoxazole. 12. No history of other enteric infections or diarrheal illness within 3 months of enrollment. In order to be eligible to participate in Part B of this trial, an individual must meet all of the following criteria: 1. Provides written informed consent prior to the initiation of any trial procedures. 2. Is able to understand and agrees to comply with all planned trial procedures and be available for all study visits, including: 1. Receiving 28 days of blinded oral study product 2. Providing blood and self-collected stool samples 3. Is non-pregnant individual, aged 18-75 years, inclusive, at the time of enrollment. 4. Has no more than 1 single Grade 1 hematology result and no more than 1 Grade 1 metabolic panel result. If the participant has more than 1 Grade 1 abnormality, it must be approved by the MM. 5. Participants of childbearing potential: use of adequate contraception for at least 4 weeks prior to enrollment through 4 weeks after the last dose of blinded study product. Note: Definitions of participants of childbearing potential and adequate contraception are provided in Section 13.1. 6. To rule out live microbial products and factors that may actively modulate the gut microbiome, participant agrees to refrain from ingestion of probiotics\* or fermented foods\*\* from 7 days prior to study product administration, while on blinded study product, and through Day 36 (Visit 6). \* E.g., probiotic nutritional Lactobacillus or Bifidobacterium supplements, yogurt, kefir, any "live and active culture" nutritional product, etc. \*\* E.g., kombucha, fermented pickled vegetables, etc. 7. Stable health by medical history, vital signs, physical examination, concomitant medication review, not requiring a change in therapy or medical care for worsening disease within 1 month of enrollment. 8. Not using medications daily that may affect gut motility, gastric acidity, or baseline gut function\* within 1 month of enrollment. \*E.g., proton pump inhibitors, opioids, anti-diarrheal agents, anti-constipation agents, daily OTC "heartburn" relief medications. 9. Not using GLP-1 receptor agonists within 6 weeks of enrollment. 10. Any elective surgery (including dental) that required preoperative or postoperative antibiotics must have been completed at least 1 month prior to enrollment. 11. Must have had at least 1 of these 3 conditions: 1. History of CDI (suspected or proven) within the past 3 years, with "cure" or no symptoms for at least 1 month prior to enrollment 2. History of a hospitalization within the past 3 years, but discharge not sooner than 1 month prior to enrollment 3. History of receiving systemic antibiotics known to increase the risk of CDI\* within the past 3 years, but last dose not sooner than 1 month prior to enrollment \*Systemic antibiotics that are known to increase risk of CDI include lincosamides (e.g., clindamycin), monobactams (e.g., aztreonam), extended-spectrum penicillin combinations with beta-lactamase inhibitors (e.g., piperacillin-tazobactam), carbapenems (e.g., imipenem, meropenem, ertapenem), third generation or higher cephalosporins, and fluoroquinolones. Common oral antibiotics that would be allowable or are not known to significantly increase the risk of CDI include amoxicillin, azithromycin, cephalexin, doxycycline, metronidazole, and trimethoprim/sulfamethoxazole. 12. No history of other enteric infections or diarrheal illness within 1 month of enrollment. Exclusion Criteria: 1. Dwells in a long-term care or skilled nursing facility (living independently with limited nursing care is allowable). 2. Known to be pregnant or has a positive pregnancy test at screening or enrollment. 3. Currently breastfeeding a child. 4. Known to have significant hypersensitivity to any components of the study product; including S. boulardii (or any S. boulardii-based nutritional supplement), hydroxypropyl methylcellulose, and Microcrystalline cellulose \[MCC\]. Hydroxypropyl methylcellulose is the major component of the capsule shell and MCC is the placebo component. 5. Known to have significant hypersensitivity to a first-line antifungal therapy (i.e., fluconazole or amphotericin B) against Saccharomyces. 6. Known to be immunocompromised or have known or suspected congenital or acquired immunodeficiency, as determined by the investigator. 7. Receipt of immunosuppressive therapy such as anti-cancer chemotherapy or radiation therapy within 3 years of enrollment. 8. Receipt of chronic (\>/=14 days) immunosuppressive corticosteroids at a dose of \>/=20 mg prednisone daily or prednisone equivalent within 30 days of enrollment, including oral, parenteral, or high-dose inhaled\* corticosteroids. \*High-dose inhaled corticosteroid is defined as \>800 mcg/day of beclomethasone dipropionate CFC or equivalent. Intra-articular, intranasal, and topical steroids are allowable. 9. Active malignancy or history of malignancy in the past 3 years (non-melanoma, excised, cured skin cancers are allowed). 10. History of or testing positive for human immunodeficiency virus (HIV), hepatitis B, or active hepatitis C at screening (positive hepatitis C antibody and detectable hepatitis C virus RNA). 11. Anticipated or current receipt of kidney dialysis treatment. 12. Concurrent, acutely life-threatening disease or condition, or any unstable medical history, as determined by the investigator. 13. Significant chronic gastrointestinal \[GI\] condition(s) or disease\*. \*Includes diagnosis of inflammatory bowel disease or active Rome IV irritable bowel syndrome, poorly controlled Celiac disease, active gastroparesis, toxic megacolon, colostomy, intestinal resection (except uncomplicated appendectomy), ileus, short gut syndrome, or recent (within 6 months of enrollment) diverticular bleeding requiring surgical intervention or transfusion. 14. Recent (within 6 months of enrollment) history of difficulty with swallowing food, liquids, or pills. 15. Prosthetic heart valve or indwelling foreign structure within vascular supply (e.g., no central line or indwelling catheter) or known to have moderate to severe valvular disease. 16. History of alcohol abuse or drug addiction within 5 years of enrollment or that might interfere with the ability to comply with trial procedures. 17. Diagnosis of schizophrenia, bipolar disease, or other significant psychiatric disease in the opinion of the investigator that may interfere with or pose a problem with compliance with the study or the welfare of the participant. 18. Presence of mild, acute, or self-limited condition, such as fever or cough or other symptoms of upper respiratory tract infection within 7 days prior to planned randomization. 19. Any chronic illness that, in the opinion of the investigator, is at a stage where it might interfere with trial conduct or completion or participant safety. 20. Identified as a study site or contract research organization employee or family member who is involved in the protocol and may have direct access to trial-related data. 21. Participating in another clinical trial investigating a vaccine, drug, medical device, or medical procedure within 4 weeks of enrollment through the last visit of the study.
Get updates
Get notified about this study
Sign up to get updates when this study changes or when new studies for Clostridium difficile infection are added.
Genom att skicka in godkänner du våra Användarvillkor
Conditions
The condition(s) this trial relates to.
As listed by the trial registrant
The condition terms exactly as the trial's registrant entered them.
How to take part
Only the study team decides who joins. These are the ways to reach them.
-
The official record
ClinicalTrials.gov lists the study team's own contact details, including names and phone numbers. We don't republish those.
-
A doctor treating you
A doctor who knows your case can contact a study site on your behalf, and can tell you whether this study is worth pursuing at all.
More trials for these conditions
Other studies related to the condition(s) this trial covers.
- Gut bacteria and genes eyed as keys to predicting repeat c. diff
- New database aims to speed up FMT research for gut infections
- Should cancer patients get antibiotics for a dubious c. diff test? small trial seeks answers
- Poop pills? fecal transplants show promise for gut infections
- Poop pills? no, stool transplants aim to cure recurrent c. diff
- 4,000 patients join landmark poop transplant safety study