The purpose of this study is to see whether Ozanimod is safe and effective for treating Crohn's disease. Adult participants (at least 18 years old) with moderately to severely active Crohn's disease may be eligible.

To do this, a comparison will be made between subjects who receive active drug and subjects who receive placebo (a ‘dummy treatment' that looks like the active drug but contains no active ingredient). The chance of being randomized (like drawing names out of a hat) into ozanimod group and receiving ozanimod is 50%. The chance of being randomized into placebo group and receiving placebo is 50%.

If participants' Crohn's disease condition get worse during the study, they will be invited to participate the open-label study, which has no placebo.

This is a one-year study, and participants are expected to come to MUSC every 8 weeks for study visits.

The purpose of this study is to see whether Ozanimod is safe and effective for treating Crohn's disease. Participants who are aged 18 to 75 years with moderately to severely active Crohn's disease may be eligible.

To do this, a comparison will be made between subjects who receive active drug and subjects who receive placebo (a ‘dummy treatment' that looks like the active drug but contains no active ingredient). The chance of being randomized (like drawing names out of a hat) into ozanimod group and receiving ozanimod is 67%. The chance of being randomized into placebo group and receiving placebo is 33%.

This study is designed to last up to 30 weeks, including 2 screening visits, 4 study visits, and 2 follow-up visits. The study drug may improve participant's Crohn's disease condition, but this cannot be guaranteed.