A Study to Investigate Efficacy and Safety of SAR441566 in Patients With Crohn's Disease.

Inclusion Criteria:

Participants are eligible to be included in the study only if all of the following criteria apply:

1. Male or female participants aged 18 to 75 years at the time of signing the ICF

2. Confirmed diagnosis of CD for at least 3 months prior to Baseline

3. Confirmed diagnosis of moderate to severe CD as assessed by:

• Crohn's Disease Activity Index (CDAI) score and the Simple Endoscopic Score forCrohn's disease (SES-CD) on an endoscopy confirmed by a central reader

• stool frequency (SF), abdominal pain (AP) score

4. History of prior exposure to standard treatment (5-ASA, steroids, immunomodulatorsor antibiotics) or advanced therapies (biologics or small molecules), but havinginadequate response to, loss or response to or intolerance to at least one of thesetherapies

5. On stable doses of standard treatments prior to screening (Oral 5-ASA compounds,Oral corticosteroids, AZA, 6-MP, or MTX ..)

6. Contraceptive use by men and women should be consistent with local regulationsregarding the methods of contraception for those participating in clinical studies.Women participants should not be pregnant or breastfeeding.

Exclusion Criteria:

Participants are excluded from the study if any of the following criteria apply:

1. Participants with active UC, indeterminate colitis or short bowel syndrome

2. Participants with CD isolated to the stomach, duodenum, jejunum, or peri analregion, without colonic or ileal involvement

3. Participants with following ongoing known complications of CD: fistula, abscess,symptomatic stricture/stenosis, fulminant colitis, toxic megacolon, recent bowelresection within 3 months of screening or history of > 3 bowel resections

4. Participants with stool sample positive for infectious pathogens

5. Participants with active tuberculosis (TB) or a history of incompletely treatedactive or latent TB per local guidelines

6. Participants with Positive Hepatitis B surface antigen (HBsAg) or positive HepatitisB core antibody (HBcAb); and/or positive Hepatitis C antibody (HCV) at the ScreeningVisit

7. Participants with any other active, chronic or recurrent infection, includingrecurrent or disseminated herpes zoster or disseminated herpes simplex

8. Participants with a known history of Human Immunodeficiency Virus (HIV) infection orpositive HIV-1 or HIV-2 serology at screening

9. Participants presenting with active malignancies, lymphoproliferative disease, orrecurrence of either, within the 5 years before screening

10. Participants with adenomatous colonic polyps or colonic mucosal dysplasia (low- orhigh grade) not excised or incompletely excised

11. Infection(s) requiring treatment with IV anti infectives within 30 days ororal/intramuscular anti-infectives within 14 days prior to the screening visit

12. Participants requiring or receiving any parental nutrition and/or exclusive enteralnutrition

13. Participants who received cyclosporine, tacrolimus, mycophenolate mofetil, orthalidomide within 30 days prior to screening

14. Participants who received fecal microbial transplantation within 30 days prior toscreening

15. Participants who have ever been exposed to natalizumab (Tysabri®) or oralcarotegrast methyl (Carogra®)

16. Participants who received IV corticosteroids within 14 days prior to screening orduring screening period

17. Participants who received therapeutic enema or suppository, other than required forcolonoscopy within 14 days prior to screening or during screening

18. Screening laboratory and other analyses show abnormal results