A Study to Investigate Efficacy and Safety of SAR441566 in Patients With Ulcerative Colitis

Inclusion Criteria: Participants are eligible to be included in the study only if all of the following criteria apply: * Male or female participants aged 18 to 75 years inclusive, at the time of signing the informed consent * Participants who have clinical evidence of active UC for ≥3 months before screening and confirmed by endoscopy during the screening period * Active moderate-to-severe UC at screening as defined by a modified Mayo Score (mMS) of 5 to 9 (without the Physician global Assessment (PGA), with a minimum rectal bleeding (RB) subscore ≥1, a minimum stool frequency (SF) subscore ≥1, a mMES ≥2 confirmed by central reader, a minimum sum of all subscores of 5, and a disease extent \>15 cm from the anal verge * Must have received prior treatment for UC (either "a" or "b" below or combination of both): 1. No prior exposure to Advanced Therapy (AT), but having inadequate response to, loss of response to or intolerance to standard treatment with any of the following compounds: 5-ASA, 6-MP, AZA, MTX, oral or intravenous (IV) corticosteroids or history of corticosteroid dependence (defined an inability to successfully taper corticosteroids without recurrence of UC) OR 2. Inadequate response to, loss of response to or intolerance to treatment with ≥1 approved AT such as a biologic agent (such as TNF antagonists, anti-integrin other than natalizumab, anti-IL-12/23, anti-IL-23, or experimental biologic UC therapeutics), or a small molecule (such as a JAKi or S1PRm) for UC * Contraceptive use by men and women should be consistent with local regulations regarding the methods of contraception for those participating in clinical studies. Exclusion Criteria: Participants are excluded from the study if any of the following criteria apply: * Participants with active CD, indeterminate colitis, ischemic colitis, microscopic colitis * Participants with the following ongoing known complications of UC: fulminant colitis, toxic megacolon, or any other manifestation that might require bowel surgery while enrolled in the study * Participant with prior colectomy, ostomy or ileoanal pouch, or anticipated colectomy during their participation in the study * Participants with fecal sample positive for ova or parasites, bacterial pathogens, or positive for Clostridium difficile B toxin in stools * Participants with active tuberculosis (TB) or a history of incompletely treated active TB or latent TB infection per local guidelines * Participants with Positive Hepatitis B surface antigen (HBsAg), or Hepatitis B core antibody (HBcAb) and/or Hepatitis C virus antibody (HCVAb) at the screening visit * Participants with any other active, chronic or recurrent infection, including recurrent or disseminated herpes zoster or disseminated herpes simplex * Participants with a known history of human immunodeficiency virus (HIV) infection or positive HIV-1 or HIV-2 serology at screening * Participants presenting with active malignancies, lymphoproliferative disease, or recurrence of either, within the 5 years before screening * If the participant has extensive colitis for ≥8 years or disease limited to left side of colon (ie, distal to splenic flexure) for \>10 years, regardless of age, a colonoscopy within 1 year of the screening visit is required to survey for dysplasia. Participants with dysplasia or cancer identified on biopsies will be excluded. * Female participants who is pregnant, breastfeeding, or is considering becoming pregnant during the study or within 3 months after the last dose of study drug * Infection(s) requiring treatment with IV anti-infectives within 30 days prior to the screening visit or oral/intramuscular anti-infectives within 14 days prior to the screening visit * Participants requiring or receiving any parental nutrition and/or exclusive enteral nutrition * Participants who received cyclosporine, tacrolimus, mycophenolate mofetil, or thalidomide within 30 days prior to screening * Participants who received fecal microbial transplantation within 30 days prior to screening * Participants who have ever been exposed to natalizumab (Tysabri®) or oral carotegrast methyl (Carogra®) * Participants who received IV corticosteroids within 14 days prior to screening or during screening period * Screening laboratory and other analyses show abnormal results. The above information is not intended to contain all considerations relevant to a participant's potential participation in a clinical trial.