This is a parallel, placebo-controlled, multicenter, randomized, double-blind, Phase 2, proof of concept study. The study aims to evaluate the efficacy and safety of SAR444336 in adult participants with microscopic colitis. Participants are required to have a histologically confirmed diagnosis of microscopic colitis, be in clinical remission and be receiving budesonide therapy. The overall study duration is approximately 32 weeks.

Inclusion Criteria:

• Participants with histologically confirmed diagnosis of microscopic colitis (including all histological sub-types).
• Receiving budesonide therapy.
• Documented clinical remission from 2 weeks before screening.
• At least 1 microscopic colitis relapse in the last 8 months prior to screening that required treatment with budesonide.
• Body mass index within the range 18 to 35 kg/m2 (inclusive) at screening visit.
• All contraceptive methods used by participants should be consistent with local regulations regarding the methods of contraception.

Exclusion Criteria:

• Significant neutrophilic/eosinophilic infiltration, crypt abscesses, granulomata, or any evidence of IBD other than microscopic colitis.
• Evidence of infectious diarrhea in the 3 months prior to randomization.
• Other active diarrheal conditions or suspicion of drug--induced microscopic colitis at screening, or diarrhea predominant irritable bowel syndrome.
• Any current active viral, bacterial, or fungal infection or any medically relevant infection having occurred within 3 weeks before randomization.
• Previous bowel surgeries.
• Planned surgery while receiving study treatment. Dental surgeries or other types of minor surgery requiring only local anesthetic are allowed.
• Other immunologic disorder, except controlled diabetes or thyroid disorder receiving appropriate treatment.
• Presence or history of drug hypersensitivity associated with eosinophilia in the past 6 months.
• History or presence of alcohol or illicit drug abuse within the past 2 years.
• Excessive consumption of beverages containing xanthine bases.
• History of solid organ transplant.
• Active malignancy, lymphoproliferative disease, or malignancy in remission for less than 2 years, except adequately treated (cured) localized carcinoma in situ of the cervix or ductal breast, or squamous cell carcinoma, or basal cell carcinoma of the skin.
• Have experienced any of the following within 12 months before screening: myocardial infarction, unstable ischemic heart disease, stroke, or New York Heart Association Stage III or IV heart failure.
• Participants with a history or presence of another significant illness such as renal, neurological, ophthalmological, psychiatric, endocrine, cardiovascular, gastrointestinal, hepatic disease, metabolic, pulmonary or lymphatic.
• Live attenuated vaccines within 6 weeks of randomization and during the study.
• Currently receiving or had treatment within 12 months prior to screening with B or T cell depleting agents.
• At screening, have abnormal laboratory values or ECG abnormalities.
• Participants with recent tuberculosis (TB) vaccination or positive TB test results.

The above information was not intended to contain all considerations relevant to a participant's potential participation in a clinical trial.

Qualified researchers may request access to patient level data and related study documents including the clinical study report, study protocol with any amendments, blank case report form, statistical analysis plan, and dataset specifications. Patient level data will be anonymized and study documents will be redacted to protect the privacy of trial participants. Further details on Sanofi's data sharing criteria, eligible studies, and process for requesting access can be found at: https://vivli.org