The Clostridioides Difficile Trial of REC-3964 (ALDER)

A Phase 2 Clinical Study of REC-3964 in Adults for the Reduction of Recurrent Clostridioides Difficile Infection (CDI)

This is a multi-center, open-label study to investigate the safety, tolerability, pharmacokinetics (PK) and efficacy of REC-3964 (doses of either 250 mg or 500 mg PO every 12 hours) for the reduction of Clostridioides difficile infection (CDI).

Study Overview

• Status: Terminated
• Conditions: Recurrent Clostridioides Difficile Infection
• Intervention / Treatment: Drug: REC-3964

Detailed Description

Study was terminated due to sponsor decision. This decision was not related to safety concerns.

• Study Type: Interventional
• Enrollment (Actual): 3
• Phase: Phase 2

Contacts and Locations

Study Locations

• United States
  • New Jersey
    • Toms River, New Jersey, United States, 08755
      • GANJ - Toms River - Ocean Family Gastroenterology
  • Texas
    • San Antonio, Texas, United States, 78229
      • Southern Star Research Institute, LLC

Participation Criteria

Eligibility Criteria

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

Description

Key Inclusion Criteria:

• Be 18 years of age or older with Clostridioides difficile infection (CDI) diarrhea associated with a positive stool test for C. difficile toxin[s] prior to the preceding curative treatment.
• The CDI episode, severe or otherwise, must have resolved after receiving vancomycin with a standard duration of treatment. The participant must be randomized within 2 days of completing the preceding curative treatment.
• Have high risk for rCDI (a recurrent CDI episode within the last 6 months, age ≥65 years, immunocompromised state, or severe CDI with resolution prior to enrollment into the study).

Key Exclusion Criteria:

• Have an active, symptomatic, chronic diarrheal illness from other causes, such as ulcerative colitis or Crohn's disease.
• Diarrhea that requires on-study treatment with agents that would confound the interpretation of the study results.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: REC-3964 High-dose; Participants will receive 500 mg REC-3964 q12h REC-3964 250 mg capsules	Drug: REC-3964; REC-3964 given at a dose of either 500 mg q12h or 250 mg q12h
No Intervention: Observation; Participants will undergo watchful waiting
Experimental: REC-3964 Low-dose; Participants will receive 250 mg REC-3964 q12h REC-3964 250 mg capsules	Drug: REC-3964; REC-3964 given at a dose of either 500 mg q12h or 250 mg q12h

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Number of Participants With Survival Without Recurrence or Requirement for Additional Clostridioides Difficile Infection (CDI) Treatment	Recurrent CDI was defined as a new episode of CDI associated with a new positive Clostridioides difficile stool toxin or requirement for additional CDI treatment during the 8-week Follow-up Period after cure of preceding CDI with initial curative treatment.	8 weeks
Number of Participants With Treatment-emergent Adverse Events (TEAEs)	A TEAE was the development of an undesirable medical condition or the deterioration of a pre-existing medical condition following or during exposure to a pharmaceutical product, whether or not considered causally related to the product.	Up to 8 weeks
Number of Participants With Related TEAEs	A TEAE was the development of an undesirable medical condition or the deterioration of a pre-existing medical condition following or during exposure to a pharmaceutical product, whether or not considered causally related to the product. An Investigator who was qualified in medicine determined relationship to the study drug for each AE (unrelated or related). The Investigator decided whether, in his or her medical judgment, if there was a reasonable biological possibility that the event may have been caused by the study drug.	Up to 8 weeks
Number of Participants With Serious TEAEs	A TEAE was the development of an undesirable medical condition or the deterioration of a pre-existing medical condition following or during exposure to a pharmaceutical product, whether or not considered causally related to the product. A Serious TEAE was defined as results in death, immediately life-threatening, requires in-participant hospitalization or prolongation of existing hospitalization, results in persistent or significant disability or incapacity in conducting activities of daily living for at least 28 days, results in a congenital abnormality or birth defect, or an important medical event that may jeopardize the participant or may require medical intervention.	Up to 8 weeks
Number of Participants With TEAEs Leading to Study Drug Discontinuation	A TEAE was the development of an undesirable medical condition or the deterioration of a pre-existing medical condition following or during exposure to a pharmaceutical product, whether or not considered causally related to the product.	Up to 8 weeks

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Maximum Observed Plasma Concentration (Cmax) of REC-3964		Pre-dose, 1 hour, 3 hours, and 6 hours post morning dose on Day 1 and Day 15
Time to Maximum Plasma Concentration (Tmax) of REC-3964		Pre-dose, 1 hour, 3 hours, and 6 hours post morning dose on the Day 1 and Day 15
Trough Plasma Concentration (Ctrough) of REC-3964		Pre-dose on Day 15
Rate of Recurrent Clostridioides Difficile Infection (rCDI)	Recurrent CDI was defined as a new episode of CDI associated with a new positive Clostridioides difficile stool toxin within 8 weeks of the cessation of initial curative treatment. The number of unformed [types 5-7 on the Bristol stool scale] bowel movements per day were recorded by the participant in the stool diary in order to identify a new episode of diarrhea. All new episodes of diarrhea were tested for toxigenic Clostridioides difficile to confirm CDI recurrence. The rate of rCDI was defined as the proportion of participants who had the Clostridioides difficile recurrence among randomized participants.	8 weeks
Time to Recurrence of rCDI	Recurrent CDI was defined as a new episode of CDI associated with a new positive Clostridioides difficile stool toxin within 8 weeks of the cessation of initial curative treatment. The number of unformed [types 5-7 on the Bristol stool scale] bowel movements per day were recorded by the participant in the stool diary in order to identify a new episode of diarrhea. All new episodes of diarrhea were tested for toxigenic Clostridioides difficile to confirm CDI recurrence. Time to recurrence of rCDI was to be assessed using Kaplan-Meier estimation.	Up to 8 weeks
Number of Participants With Severe rCDI	Recurrent CDI was defined as a new episode of CDI associated with a new positive Clostridioides difficile stool toxin within 8 weeks of the cessation of initial curative treatment. The number of unformed [types 5-7 on the Bristol stool scale] bowel movements per day were recorded by the participant in the stool diary in order to identify a new episode of diarrhea. All new episodes of diarrhea were tested for toxigenic Clostridioides difficile to confirm CDI recurrence. Severe CDI was defined as CDI with white blood cell count >15,000 cells/milliliter and/or serum creatinine ≥1.5 milligram/deciliter.	Up to 8 weeks
Number of Participants With rCDI Who Had Associated Hospital Admissions	Recurrent CDI was defined as a new episode of CDI associated with a new positive Clostridioides difficile stool toxin within 8 weeks of the cessation of initial curative treatment. The number of unformed [types 5-7 on the Bristol stool scale] bowel movements per day were recorded by the participant in the stool diary in order to identify a new episode of diarrhea. All new episodes of diarrhea were tested for toxigenic Clostridioides difficile to confirm CDI recurrence.	Up to 8 weeks

Collaborators and Investigators

• Sponsor: Recursion Pharmaceuticals Inc.

Study record dates

Study Major Dates

• Study Start (Actual): October 14, 2024
• Primary Completion (Actual): May 6, 2025
• Study Completion (Actual): May 6, 2025

Study Registration Dates

• First Submitted: July 15, 2024
• First Submitted That Met QC Criteria: July 31, 2024
• First Posted (Actual): August 5, 2024

Study Record Updates

• Last Update Posted (Actual): November 17, 2025
• Last Update Submitted That Met QC Criteria: November 4, 2025
• Last Verified: November 1, 2025

More Information

Terms related to this study

• Keywords: Cdiff Infection; Clostridiodes difficile infection; Cdiff
• Additional Relevant MeSH Terms: Infections; Gram-Positive Bacterial Infections; Bacterial Infections; Bacterial Infections and Mycoses; Clostridium Infections
• Other Study ID Numbers: REC-3964-201

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.: No