A Study Evaluating the Efficacy and Safety of Oral Etrasimod in the Treatment of Adult Participants With Moderately to Severely Active Crohn's Disease

Eligibility criteria applicable to all substudies:

Inclusion Criteria:

• Men or women 18 to 80 years of age,

• Ability to provide written informed consent or assent and to be compliant with theschedule of protocol assessments

• Diagnosed with Crohn's disease (CD) ≥ 3 months

• Have moderately to severely active CD at Screening

• Demonstrated inadequate response (ie, primary non-response), loss of response to, orintolerance to ≥ 1 of the following therapies for the treatment of CD:

1. Oral corticosteroids (eg, prednisone or its equivalent, budesonide)

2. Immunosuppressants (eg, azathioprine [AZA], 6 mercaptopurine [6-MP], ormethotrexate [MTX])

3. Tumor necrosis factor alpha (TNFα) antagonists (eg, infliximab, adalimumab,certolizumab pegol, or biosimilars)

4. Integrin receptor antagonist (eg, vedolizumab)

5. Interleukin -12/-23 antagonist (eg, ustekinumab)

• Females of childbearing potential must be nonpregnant

• Females of childbearing potential and males must use contraception

Exclusion Criteria:

• History of inadequate response (ie, primary non-response) to agents from ≥ 2 classesof biologics marketed for the treatment of CD (ie, TNFα antagonists, interleukin 12/ 23 antagonist, and integrin receptor antagonist).

• Have ulcerative colitis, indeterminate colitis, microscopic colitis, ischemiccolitis, radiation colitis, diverticular disease associated colitis, toxicmegacolon, or active infectious colitis or test positive for Clostridioidesdifficile toxin at Screening.

• Have functional or post-operative short-bowel syndrome or any associatedcomplications that may require surgery or interfere with efficacy assessments

• Had surgical treatment for intra abdominal abscesses ≤ 8 weeks prior torandomization or surgical treatment for perianal abscesses ≤ 4 weeks prior torandomization.

• Had intestinal resection ≤ 24 weeks prior to randomization or other intra abdominalsurgeries ≤ 12 weeks prior to randomization.

• Have an ileostomy or a colostomy.

Inclusion Criteria for Substudy 3:

• Participants who entered the Extended Induction Period of Substudy 1 and Substudy 2must have completed the Extended Induction -Week 6 Visit

Inclusion Criteria for Substudy 4:

• Participant must have completed the Week 52 Visit of Substudy 3 or the Week 66 Visitof Substudy A