Ruxolitinib (trade names Jakafi and Jakavi, by Incyte Pharmaceuticals and Novartis) is a drug for the treatment of intermediate or high-risk myelofibrosis, a type of myeloproliferative disorder that affects the bone marrow. It is also being investigated for the treatment of other types of cancer (such as lymphomas and pancreatic cancer), for polycythemia vera, for plaque psoriasis, and for alopecia areata. Myelofibrosis (MF) is a myeloproliferative neoplasm (MPN) known to be associated with dysregulated JAK1 and JAK2 signaling. Ruxolitinib is a Janus-associated kinase (JAK) inhibitor with potential antineoplastic and immunomodulating activities. Ruxolitinib specifically binds to and inhibits protein tyrosine kinases JAK 1 and 2, which may lead to a reduction in inflammation and an inhibition of cellular proliferation. The JAK-STAT (signal transducer and activator of transcription) pathway plays a key role in the signaling of many cytokines and growth factors and is involved in cellular proliferation, growth, hematopoiesis, and the immune response; JAK kinases may be upregulated in inflammatory diseases, myeloproliferative disorders, and various malignancies. In a mouse model of JAK2V617F-positive MPN, ruxolitinib prevented splenomegaly, preferentially decreased JAK2V617F mutant cells in the spleen and decreased circulating inflammatory cytokines (eg, TNF-α, IL-6). Ruxolitinib was initially synthesized at Incyte Corporation that acquired the rights to develop and commercialize the drug in US. Incyte amended its Collaboration and License Agreement with Novartis, granting Novartis exclusive research, development and commercialization rights for ruxolitinib outside the U.S.