Used as the phosphate salt for the treatment of patients with intermediate or high-risk myelofibrosis, including primary myelofibrosis, post-polycythemia vera myelofibrosis and post-essential thrombocythemia myelofibrosis. It has a role as an antineoplastic agent and an EC 2.7.10.2 (non-specific protein-tyrosine kinase) inhibitor.