The purpose of this study is to assess the real-world safety of fedratinib for the treatment of adult participants with primary myelofibrosis (PMF), post polycythemia vera myelofibrosis (post-PV MF), or post essential thrombocythemia myelofibrosis (post-ET MF) who were previously treated with ruxolitinib. Participants will represent the overall patient population with PMF, post-PV MF or post-ET MF who lost adequate response to and/or are intolerant to ruxolitinib. Inadequate response definitions will follow Ministry of Food and Drug Safety-approved label and reimbursement criteria of the Health Insurance Review \& Assessment Service.
Participants 19 years of age or older
Participants who will receive fedratinib according to the approved label
For the first 2 years after marketing authorization, all participants who have received or are receiving fedratinib will also be registered
Participants who signed the informed consent form
Participants who have been prescribed fedratinib for an indication not approved in Korea
Participants who have been prescribed fedratinib at a dose not approved in Korea
Participants for whom fedratinib is contraindicated as clarified in Korean prescribing information approved by the Ministry of Food and Drug Safety