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

Inclusion Criteria:

1. Men or women 18 to 80 years of age,
2. Ability to provide written informed consent or assent and to be compliant with the schedule of protocol assessments
3. Diagnosed with Crohn's disease (CD) ≥ 3 months
4. Have moderately to severely active CD at Screening

Demonstrated inadequate response (ie, primary non-response), loss of response to, or intolerance 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], or methotrexate [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)
6. Females of childbearing potential must be nonpregnant
7. Females of childbearing potential and males must use contraception

Inclusion Criteria for Substudy 3:

Inclusion Criteria for Substudy 4:

Exclusion Criteria:

1. History of inadequate response (ie, primary non-response) to agents from ≥ 2 classes of biologics marketed for the treatment of CD (ie, TNFα antagonists, interleukin 12/ 23 antagonist, and integrin receptor antagonist).
2. Have ulcerative colitis, indeterminate colitis, microscopic colitis, ischemic colitis, radiation colitis, diverticular disease associated colitis, toxic megacolon, or active infectious colitis or test positive for Clostridioides difficile toxin at Screening.
3. Have functional or post-operative short-bowel syndrome or any associated complications that may require surgery or interfere with efficacy assessments
4. Had surgical treatment for intra abdominal abscesses ≤ 8 weeks prior to randomization or surgical treatment for perianal abscesses ≤ 4 weeks prior to randomization.
5. Had intestinal resection ≤ 24 weeks prior to randomization or other intra abdominal surgeries ≤ 12 weeks prior to randomization.
6. Have an ileostomy or a colostomy.

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

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