Ruxolitinib is a drug for the treatment of intermediate or high-risk myelofibrosis, a type of myeloproliferative disorder that affects the bone marrow, and for polycythemia vera (pcv) when there has been an inadequate response to or intolerance of hydroxyurea.ruxolitinib is a janus kinase inhibitor with selectivity for subtypes jak1 and jak2 of this enzyme. ruxolitinib inhibits dysregulated jak signaling associated with myelofibrosis. jak1 and jak2 recruit signal transducers and activators of transcription (stats) to cytokine receptors leading to modulation of gene expression.