Exelixis has submitted an IND application to the FDA for XL019. In preclinical studies, the compound has shown to be a potent, selective and orally available small molecule inhibitor of the cytoplasmic tyrosine kinase JAK2, according to the company. Activating mutations in JAK2 are frequently observed in patients with myeloproliferative disorders such as myelofibrosis, polycythemia vera and essential thrombocythemia. JAK2 activity is also upregulated via multiple mechanisms in many lymphomas and...