This is a mutli-center open-label study to provide continued supply of itacitinib to participants from the following Incyte-sponsored studies of itacitinib: INCB39110-209, INCB39110-213, INCB39110-214, INCB39110-230, and 39110-309. Eligible participants will receive treatment with itacitinib as per the treatment dose and schedule they received in the study in which they were originally enrolled. The original study is referred to as the "parent protocol". Participants who receive itacitinib in this study may continue treatment as long as the regimen is tolerated, the participant is deriving clinical benefit (in the opinion of the investigator), and the participant does not meet discontinuation criteria.