Phase I/II Evaluation of EXL01 for Prevention of Clostridioides difficile Infection Recurrence in High-Risk Patients Treated with Oral Vancomycin

The primary objective of this study is to evaluate the **safety** and tolerability of oral EXL01 in Phase I, and to assess the efficacy of EXL01 in preventing the recurrence of **Clostridioides difficile** infection at week 8 (S8) in patients at high risk of recurrence in Phase II. This is clinically relevant as it addresses the need for effective prevention strategies in patients with multiple recurrences of C. difficile infection, a condition often treated with oral Vancomycin.

Secondary objectives include:

• Phase I: Evaluation of the efficacy of EXL01 in preventing recurrence of C. difficile infection at S8 in high-risk patients.
• Phase II: Evaluation of the safety and tolerability profile of oral EXL01.
• Assessment of digestive symptoms during treatment and follow-up.
• Assessment of the patient's quality of life during treatment and follow-up.
• Assessment of recurrence of C. difficile infection at month 4 (M4).
• Assessment of the presence of EXL01 in the fecal microbiota at S8.
• Assessment of the persistence of EXL01 in the intestinal microbiota at M4.
• Assessment of the composition of the intestinal microbiota during treatment.
• Assessment of the persistence of toxigenic C. difficile in the feces of patients in clinical remission during the study.
• Assessment of recurrence of C. difficile infection requiring hospitalization at S8 and M4.
• Assessment of recurrences of C. difficile infection requiring surgery at S8 and M4.

The clinical trial involves participants with **multiple recurrences of Clostridioides difficile infection** treated with oral Vancomycin. The study population includes both male and female subjects over the age of 18, with no specific vulnerable populations selected. Participants are required to have experienced either a third episode of proven C. difficile infection within six months or a second episode with specific risk factors, such as age over 70, chronic renal failure, or a history of severe CDI. The trial does not specify the total number of participants, as this information was not provided by the sponsor. Participants are expected to be on current or planned vancomycin treatment and must be capable of providing informed consent. They should also be enrolled in the national compulsory social security scheme. The trial population was selected based on these criteria, focusing on individuals at high risk of recurrence. Lifestyle considerations such as diet and physical activity are not detailed in the available data.

The clinical trial is designed to evaluate the safety, tolerability, and efficacy of **EXL01**, a new Live Biotherapeutic Product, in preventing the recurrence of **Clostridioides difficile** infection in high-risk patients. This is a Phase I/II trial, which is randomized, double-blind, and controlled. The trial is expected to commence on November 6, 2023, and conclude by July 6, 2026. Participants will be involved in the study for a duration that includes multiple visits, starting with an inclusion (screening) visit, followed by several follow-up visits, and concluding with an end-of-study visit.

The inclusion visit will assess eligibility based on criteria such as age over 18 years, a history of multiple recurrences of **C. difficile** infection, and current or planned treatment with oral **Vancomycin**. Participants must be capable of providing informed consent and be enrolled in the national compulsory social security scheme. Follow-up visits will occur at specified intervals to monitor the occurrence of adverse events, digestive symptoms, and the composition of the intestinal microbiota. The primary endpoint for Phase I is the occurrence of serious adverse events, while Phase II focuses on the proportion of patients experiencing a recurrence of **C. difficile** infection.

The expected length of participant involvement will vary depending on individual response to treatment and the occurrence of any adverse events. Conditions that may lead to early termination from the study include the occurrence of serious adverse events or the participant's decision to withdraw consent. The study aims to provide comprehensive data on the safety and efficacy of **EXL01** in preventing the recurrence of **C. difficile** infection, contributing valuable insights into the management of this condition in high-risk populations.

The clinical trial involves the evaluation of **EXL01**, a novel **Live Biotherapeutic Product** designed to prevent the recurrence of **Clostridioides difficile infection** in high-risk patients. **EXL01** is administered in the form of a hard capsule, with the active substance being a structurally diverse substance. The administration route is oral, and the dosing schedule is determined based on the trial phase and participant response. Compliance with the dosing regimen is monitored through regular follow-ups and participant diaries to ensure adherence to the protocol.

In addition to **EXL01**, the trial includes the use of **VANCOMYCIN** as a comparator treatment. **VANCOMYCIN** is provided in the form of a powder for solution for infusion, with the active substance being of chemical origin. The administration route for **VANCOMYCIN** is oral, and it is used to establish a baseline for evaluating the efficacy of **EXL01**. The dosing frequency and schedule for **VANCOMYCIN** are aligned with standard clinical practices for managing **Clostridioides difficile infection**. Participant compliance with **VANCOMYCIN** administration is similarly monitored to ensure accurate assessment of treatment outcomes.

The trial does not utilize a placebo, and all treatments are administered under controlled conditions to maintain the integrity of the study. The primary objective is to assess the safety, tolerability, and efficacy of **EXL01** in preventing infection recurrence, with **VANCOMYCIN** serving as a reference point for comparison. The study is conducted in accordance with regulatory guidelines, ensuring that all participants receive appropriate care and monitoring throughout the trial duration.

The clinical trial aims to evaluate the efficacy of the investigational product **EXL01** in preventing the recurrence of Clostridioides difficile infection in high-risk patients. Efficacy will be assessed through both primary and secondary endpoints. The primary endpoint for Phase II is the proportion of patients at week 8 (S8) after the start of treatment who experience a recurrence of toxigenic C. difficile, defined as having three or more loose stools per day for more than 48 hours, along with the detection of C. difficile toxin in stool, necessitating the initiation of specific treatment for the infection.

Secondary endpoints include the occurrence of adverse events (CTCAE grade ≥3) during treatment and follow-up, discontinuation of treatment due to adverse events, and various measures of digestive symptoms. These symptoms will be evaluated at each visit by recording the number of bowel movements per day over the last 24 hours using a stool calendar, assessing stool consistency with the Bristol scale, and measuring abdominal discomfort using a validated irritable bowel syndrome scale (IBS-SSS) at S8 and month 4 (M4). Patient quality of life will be assessed at S8 and M4 using a validated quality of life questionnaire for digestive diseases (IBS-QOL).

Additional secondary endpoints include the percentage of patients with a recurrence of C. difficile infection at M4, levels of F. prausnitzii in stools at S8 and M4 compared to baseline (S0) using qPCR, and the composition of the intestinal microbiota determined by 16S rRNA sequencing or shotgun at each visit. The trial will also monitor the percentage of patients at each visit with a positive fecal toxigenic C. difficile test (PCR) who are considered to be in clinical remission, as well as the percentage of patients with a recurrence of C. difficile infection requiring hospitalization or surgery at S8 and M4.