A Study of Itacitinib for the Prevention of Cytokine Release Syndrome Induced by Immune Effector Cell Therapy

Part 1: Itacitinib 200 mg once daily for 30 days. Part 2: Itacitinib 200 mg twice daily for 30 days.

Participants will receive IEC therapy that is approved by the health authority in the country where the study is being conducted for any approved hematologic indication.

Participants will receive placebo twice daily.

Eligible participants are receiving Yescarta (An infusion of chimeric antigen receptor (CAR)-transduced autologous T cells) for relapsed or refractory larbe B-cell lymphoma or follicular lymphoma intravenously.