NCT03595553 (Ri-CoDIFy 1) is a Phase 3 clinical trial of Ridinilazole in Clostridioides Difficile Infection, sponsored by Summit Therapeutics.

Who is sponsoring NCT03595553?

NCT03595553 is sponsored by Summit Therapeutics.

What drugs are being tested in NCT03595553?

Interventions in NCT03595553: Ridinilazole, Vancomycin.

What condition does NCT03595553 study?

NCT03595553 studies Clostridioides Difficile Infection.

Is NCT03595553 still recruiting?

NCT03595553 is currently completed. Last updated 3 March 2023.

Are results published for NCT03595553?

Yes — primary outcome results have been posted to ClinicalTrials.gov. See the outcomes section above for details.

Last reviewed 2023-03-03 · How we verify

NCT03595553: Ri-CoDIFy 1

Name: Drug Landscape Pharmaceutical Database
Creator: Drug Landscape
Published: 2026-01-01
License: https://creativecommons.org/licenses/by/4.0/

Comparison of Ridinilazole Versus Vancomycin Treatment for Clostridium Difficile Infection

Completed Phase 3 Results posted Last updated 3 March 2023

What this trial tests

Phase 3 trial testing Ridinilazole in Clostridioides Difficile Infection in 759 participants. Completed in 17 November 2021.

Timeline

28 January 2019

Primary endpoint
17 November 2021

17 November 2021

Quick facts

Lead sponsor	Summit Therapeutics
Phase	Phase 3
Status	Completed
Study type	INTERVENTIONAL
Allocation	randomized
Design	parallel
Masking	quadruple
Primary purpose	treatment
Enrollment	759
Start date	28 January 2019
Primary completion	17 November 2021
Estimated completion	17 November 2021
Sites	149 locations across New Zealand, Russia, Greece, Hungary, Poland, South Korea, Argentina, Canada

Drugs / interventions tested

Ridinilazole — full drug profile →
Vancomycin (vancomycin) — full drug profile →

Conditions studied

Clostridioides Difficile Infection — all drugs for Clostridioides Difficile Infection →

Sponsor

Summit Therapeutics — full company profile →

Who can join

18 and older, any sex, with Clostridioides Difficile Infection. Patients with the condition only — healthy volunteers not accepted.

Results — posted to ClinicalTrials.gov

Per-arm endpoint measurements with 95% confidence intervals where reported. Source: trial results section.

Number of Participants With Sustained Clinical Response (SCR) Defined as Clinical Response and no Recurrence of CDI Through 30 Days Post End of Treatment (EOT). Primary · Day 40

This primary outcome measures the number of participants with Sustained Clinical Response (SCR). SCR is defined as Clinical Response and no recurrence of CDI through 30 days post End of Treatment (EOT). At D40, D70 and D100 the Investigator or medically qualified designee will determine if the patient has a sustained clinical response or experienced RECURRENCE since the previous assessment. The Investigator will assess cure/failure and recurrence based on available information which includes, but is not limited to, improvement from baseline in the number of UBMs, signs \& symptoms of CDI, and

SCR based on Clinical Cure

Group	Value	95% CI
Ridinilazole	238
Vancomycin	225

SCR based on Clinical Cure Failure

Group	Value	95% CI
Ridinilazole	132
Vancomycin	150

Clinical Response Secondary · Day 12

defined as * less than 3 unformed bowel movements (UBMs) for consecutive days and maintained through EOT without further CDI treatment at EOT + 2 days, or * the investigator's assessment that the subject no longer needs specific CDI antimicrobial treatment after completion of the course of study medication.

Clinical Response

Group	Value	95% CI
Ridinilazole	320
Vancomycin	346

Clinical Response Failure

Group	Value	95% CI
Ridinilazole	50
Vancomycin	29

Clinical Cure Secondary · Day 12

defined as the resolution of diarrhea (\<3 UBMs in the 1-day period immediately prior to EOT, that is maintained for 2 days after EOT).

Clinical Cure

Group	Value	95% CI
Ridinilazole	275
Vancomycin	292

Clinical Cure Failure

Group	Value	95% CI
Ridinilazole	95
Vancomycin	83

Sustained Clinical Response Over 60 Days Secondary · Day 70

defined as Clinical Response and no recurrence of CDI through 60 days post EOT

Sustained Clinical Response 60 Days Post EOT

Group	Value	95% CI
Ridinilazole	262
Vancomycin	258

Sustained Clinical Response 60 Days Post EOT Failure

Group	Value	95% CI
Ridinilazole	108
Vancomycin	117

Sustained Clinical Response Over 90 Days Secondary · Day 100

defined as Clinical Response and no recurrence of CDI through 90 days post EOT

Sustained Clinical Response 90 Days Post EOT

Group	Value	95% CI
Ridinilazole	259
Vancomycin	249

Sustained Clinical Response 90 Days Post EOT Failure

Group	Value	95% CI
Ridinilazole	111
Vancomycin	126

Relative Abundance of the 3 Main Bile Acid Groups (Conjugated Primary, Primary and Secondary Bile Acids) From Baseline to EOT. Secondary · Day 10

This secondary outcome measures the relative abundance of the 3 main Bile Acid Groups (Conjugated Primary, Primary and Secondary Bile Acids) from Baseline to EOT.

Secondary Bile Acid Group at Baseline

Group	Value	95% CI
Ridinilazole	33.34	± 35.68
Vancomycin	30.25	± 34.13

Secondary Bile Acid Group at EOT

Group	Value	95% CI
Ridinilazole	38.13	± 39.63
Vancomycin	7.87	± 22.69

Primary Bile Acid Group at Baseline

Group	Value	95% CI
Ridinilazole	55.03	± 34.06
Vancomycin	57.44	± 33.08

Primary Bile Acid Group at EOT

Group	Value	95% CI
Ridinilazole	55.99	± 38.06
Vancomycin	65.72	± 33.90

Conjugated Primary Bile Acid Group at Baseline

Group	Value	95% CI
Ridinilazole	11.64	± 21.93
Vancomycin	12.31	± 21.56

Conjugated Primary Bile Acid Group at EOT

Group	Value	95% CI
Ridinilazole	5.88	± 15.50
Vancomycin	26.42	± 31.62

Percentage of Change of α-diversity (Shannon Index) of the Microbiota in Stool Samples From Baseline to EOT. Secondary · Day 10

This secondary outcome measures the percentage of change of α-diversity (Shannon Index) of the microbiota in stool samples from baseline to EOT. Shannon index is a weighted statistic measuring both species richness and evenness. The Shannon Index is calculated by taking the relative abundance of each species and sums the relative abundance times the natural log of the relative abundance for each species. The value is converted into a positive value by times minus one. A higher Shannon Index means higher diversity

Group	Value	95% CI
Ridinilazole	37.06	6.01 – 68.11
Vancomycin	-7.32	-16.61 – 1.97

Measure of β-diversity of the Gut Microbiota Between Baseline and EOT Stool Samples (Bray-Curtis Index/Dissimilarity). Secondary · Day 10

This secondary outcome measures the β-diversity of the gut microbiota in stool samples from baseline to EOT. Bray-Curtis index/dissimilarity measures how different two samples are in the microbiome composition. The Bray-Curtis dissimilarity is graded between 0 and 1, where 0 means the two samples have the same composition (that is they share all the species and every species has the same abundance), and 1 means the two samples do not share any species.

Group	Value	95% CI
Ridinilazole	0.7	0.68 – 0.72
Vancomycin	0.81	0.79 – 0.83

Adverse events — posted to ClinicalTrials.gov

Time frame: All Serious Adverse Events (SAEs) will be collected from the signing of the informed consent form (ICF) until the D100 End of Study visit. All AEs will be collected from the time and date of first dose of study treatment until the D40 follow-up visit.. Reporting threshold: 0%. Adverse-event reports describe events observed during the trial — not all are caused by the drug.

RIDINILAZOLE 200 MG

Serious: 32/374 (9%)

Deaths: 26/374

VANCOMYCIN 125 MG

Serious: 30/377 (8%)

Deaths: 24/377

Serious adverse events (62 terms)

Reaction	System	RIDINILAZOLE 200 MG	VANCOMYCIN 125 MG
COVID-19 pneumonia	Infections and infestations	—	—
Pneumonia	Infections and infestations	—	—
Urosepsis	Infections and infestations	—	—
Clostridium difficile infection	Infections and infestations	—	—
Escherichia sepsis	Infections and infestations	—	—
Pulmonary embolism	Respiratory, thoracic and mediastinal disorders	—	—
Abdominal abscess	Infections and infestations	—	—
Acute myocardial infarction	Cardiac disorders	—	—
Asthma	Respiratory, thoracic and mediastinal disorders	—	—
Cardiac failure	Cardiac disorders	—	—
Cardiac failure congestive	Cardiac disorders	—	—
Cerebrovascular accident	Nervous system disorders	—	—
Cholecystitis acute	Hepatobiliary disorders	—	—
Chronic kidney disease	Renal and urinary disorders	—	—
COVID-19	Infections and infestations	—	—
Dehydration	Metabolism and nutrition disorders	—	—
Diabetic ketoacidosis	Metabolism and nutrition disorders	—	—
Diverticulitis	Infections and infestations	—	—
Drug hypersensitivity	Immune system disorders	—	—
Empyema	Infections and infestations	—	—
Endocarditis	Infections and infestations	—	—
Enterobacter infection	Infections and infestations	—	—
Enterocolitis haemorrhagic	Gastrointestinal disorders	—	—
Escherichia infection	Infections and infestations	—	—
Escherichia urinary tract infection	Infections and infestations	—	—

Other adverse events (217 terms — click to expand)

Reaction	System	RIDINILAZOLE 200 MG	VANCOMYCIN 125 MG
Diarrhoea	Gastrointestinal disorders	—	—
Nausea	Gastrointestinal disorders	—	—
Headache	Nervous system disorders	—	—
Abdominal pain	Gastrointestinal disorders	—	—
Hypokalaemia	Metabolism and nutrition disorders	—	—
Pyrexia	General disorders	—	—
Anaemia	Blood and lymphatic system disorders	—	—
Arthralgia	Musculoskeletal and connective tissue disorders	—	—
Hypertension	Vascular disorders	—	—
Abdominal pain upper	Gastrointestinal disorders	—	—
Constipation	Gastrointestinal disorders	—	—
Dizziness	Nervous system disorders	—	—
Vomiting	Gastrointestinal disorders	—	—
Abdominal distension	Gastrointestinal disorders	—	—
Hypomagnesaemia	Metabolism and nutrition disorders	—	—
Insomnia	Psychiatric disorders	—	—
Aspartate aminotransferase increased	Investigations	—	—
Atrial fibrillation	Cardiac disorders	—	—
Blood creatinine increased	Investigations	—	—
Colitis	Gastrointestinal disorders	—	—
Decreased appetite	Metabolism and nutrition disorders	—	—
Dyspnoea	Respiratory, thoracic and mediastinal disorders	—	—
Flatulence	Gastrointestinal disorders	—	—
Haemorrhoids	Gastrointestinal disorders	—	—
Hepatic enzyme increased	Investigations	—	—
Hypocalcaemia	Metabolism and nutrition disorders	—	—
Upper respiratory tract infection	Infections and infestations	—	—
Urinary tract infection	Infections and infestations	—	—
Alanine aminotransferase increased	Investigations	—	—
Anxiety	Psychiatric disorders	—	—
Asthenia	General disorders	—	—
Back pain	Musculoskeletal and connective tissue disorders	—	—
Blood potassium decreased	Investigations	—	—
Blood potassium increased	Investigations	—	—
Blood urea increased	Investigations	—	—
Colon adenoma	Neoplasms benign, malignant and unspecified (incl cysts and polyps)	—	—
Cough	Respiratory, thoracic and mediastinal disorders	—	—
Dyspepsia	Gastrointestinal disorders	—	—
Fall	Injury, poisoning and procedural complications	—	—
Fatigue	General disorders	—	—

Most-reported serious reactions: COVID-19 pneumonia, Pneumonia, Urosepsis, Clostridium difficile infection, Escherichia sepsis, Pulmonary embolism, Abdominal abscess, Acute myocardial infarction.

Data from ClinicalTrials.gov NCT03595553 adverse events section.

Sponsor's own description

Summit is developing ridinilazole as a novel antimicrobial for Clostridioides difficile Infection (CDI), formerly known as Clostridium difficile Infection, with the goal of demonstrating an improved Sustained Clinical Response rate in subjects treated with ridinilazole as compared to subjects treated with vancomycin. A phase 2 proof of concept study, with vancomycin as comparator, demonstrated these attributes with a comparable safety profile. A high fecal concentration of ridinilazole and little systemic exposure were noted. The rationale for this phase 3 study is to confirm the improvement in sustained clinical response of CDI over vancomycin and to compare the safety and tolerability of ridinilazole to that of vancomycin. Ridinilazole plasma concentration will be assessed in a subset of patients.

Publications & conference data

8 peer-reviewed publications reference this trial (live from Europe PMC):

Antibiotics in the clinical pipeline in October 2019.
Butler MS, Paterson DL. · · 2020 · cited 174× · PMID 32152527 · DOI 10.1038/s41429-020-0291-8
A Review of Antibacterial Candidates with New Modes of Action.
Butler MS, Vollmer W, Goodall ECA, Capon RJ, et al · · 2024 · cited 49× · PMID 39018341 · DOI 10.1021/acsinfecdis.4c00218
Treatment of Clostridioides (Clostridium) difficile infection.
Oksi J, Anttila VJ, Mattila E. · · 2020 · cited 41× · PMID 31801387 · DOI 10.1080/07853890.2019.1701703
Emerging Treatment Options for Infections by Multidrug-Resistant Gram-Positive Microorganisms.
Koulenti D, Xu E, Song A, Sum Mok IY, et al · · 2020 · cited 27× · PMID 32019171 · DOI 10.3390/microorganisms8020191
A Randomized, Double-Blind, Phase 3 Safety and Efficacy Study of Ridinilazole Versus Vancomycin for Treatment of Clostridioides difficile Infection: Clinical Outcomes With Microbiome and Metabolome Correlates of Response.
Okhuysen PC, Ramesh MS, Louie T, Kiknadze N, et al · · 2024 · cited 24× · PMID 38305378 · DOI 10.1093/cid/ciad792
Emerging Options for the Prevention and Management of Clostridioides difficile Infection.
Gonzales-Luna AJ, Carlson TJ, Garey KW. · · 2023 · cited 24× · PMID 36645620 · DOI 10.1007/s40265-022-01832-x
The Urgent Threat of Clostridioides difficile Infection: A Glimpse of the Drugs of the Future, with Related Patents and Prospects.
Alshrari AS, Hudu SA, Elmigdadi F, Imran M. · · 2023 · cited 17× · PMID 36830964 · DOI 10.3390/biomedicines11020426
Management of Clostridioides difficile colitis: insights for the gastroenterologist.
Saha S, Khanna S. · · 2019 · cited 14× · PMID 31105766 · DOI 10.1177/1756284819847651

Verify or expand the search:

Other trials of Ridinilazole

Trials testing the same drug.

NCT04802837 — Safety, Tolerability and the Pharmacokinetics of Ridinilazole in Adolescent Subjects · Phase 3 · terminated

Other recruiting trials for Clostridioides Difficile Infection

Currently open trials in the same condition.

NCT07285213 — Prevention of Recurrent C. Difficile Infection Study With AZD5148 Monoclonal Antibody · Phase 2 · recruiting
NCT06979609 — Secondary Prevention of Clostridioides Difficile Using Vancomycin · Phase 2, PHASE3 · recruiting
NCT06859437 — Prevention of Clostridium Difficile Infections Using Lactobacillus Plantarum 299v Strain in Nephrology and Transplantati · NA · recruiting
NCT05330182 — LMN-201 for Prevention of C. Difficile Infection Recurrence · Phase 2, PHASE3 · recruiting
NCT06788769 — Study of Clostridioides Difficile in Infants · recruiting

Other Summit Therapeutics trials

Trials by the same sponsor.

NCT07228832 — Phase III Study of Ivonescimab or Bevacizumab Combined With FOLFOX in Patients With Metastatic Colorectal Cancer · Phase 3 · recruiting
NCT05899608 — Clinical Study of Ivonescimab for First-line Treatment of Metastatic NSCLC Patients · Phase 3 · recruiting
NCT06396065 — Phase III Study of AK112 for NSCLC Patients · Phase 3 · active not recruiting
NCT04802837 — Safety, Tolerability and the Pharmacokinetics of Ridinilazole in Adolescent Subjects · Phase 3 · terminated

Verify against primary sources

ClinicalTrials.gov — authoritative US registry record
WHO ICTRP — international registry index
EU Clinical Trials Register
Sponsor press releases (Google)

Data sources for this page

Trial protocol + status: ClinicalTrials.gov NCT03595553 (US National Library of Medicine, public domain)
Publications: Europe PMC API search by NCT ID, retrieved 10 June 2026
Drug + disease cross-links: matched in real time against Drug Landscape's normalised drug + company + condition tables
Sponsor: as reported to ClinicalTrials.gov by Summit Therapeutics
Last refreshed: 3 March 2023

Drug Landscape aggregates and links these public records for informational use only. Always verify against the primary source before clinical or regulatory decisions. Canonical URL: https://druglandscape.com/trial/NCT03595553.

Primary sources · FDA · ClinicalTrials.gov · EMA · SEC EDGAR · ChEMBL · Wikidata · full sourcing