The purpose of this study is to assess an investigational drug called etrasimod (also referred to as the “study drug”) in the treatment of Crohn’s disease (CD). This study is being done to find out which dose of etrasimod works, which is the safest dose, and how tolerable it is for people with moderate to severe CD. The study will also look at:
1. Whether etrasimod works, how safe and tolerable it is over a longer period.
2. How etrasimod affects the body (pharmacodynamics) and
3. What the body does to etrasimod (pharmacokinetics).

Your participation in the study may last for up to 74 weeks (about 1 year and 5 months). The study will have 2 treatment periods: a 14-week induction period and a further 52-week extension period. You can take part in this study if you are:
1. 18-80 Years of age;
2. Have been diagnosed with moderately to severely active CD for at least 3 months;
3. did not respond to CD therapy, responded to CD therapy at first but are no longer responding, or could not tolerate available CD therapies.

You can contact any of the individuals listed below to take part in this research study.

Inclusion Criteria:

• Ability to provide written informed consent or assent and to be compliant with the schedule 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, 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)
• Females of childbearing potential must be nonpregnant 

Exclusion Criteria:

• 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).
• 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.
• Have functional or post-operative short-bowel syndrome or any associated complications that may require surgery or interfere with efficacy assessments
• Had surgical treatment for intra abdominal abscesses ≤ 8 weeks prior to randomization or surgical treatment for perianal abscesses ≤ 4 weeks prior to randomization.
• Had intestinal resection ≤ 24 weeks prior to randomization or other intra abdominal surgeries ≤ 12 weeks prior to randomization.
• Have an ileostomy or a colostomy.