Open-Label Study of Oral CEP-701 (Lestaurtinib) in Patients With Polycythemia Vera or Essential Thrombocytosis

Inclusion Criteria: * The patient has polycythemia vera (PV) or essential thrombocytosis (ET). * The patient has a detectable JAK2 V617F mutation. * Patients with PV have at least 1 of the following risk factors: 1. neutrophil count greater than 7000/mm3 2. receiving hydroxyurea treatment * Patients with ET are receiving concomitant hydroxyurea. * The patient has an ECOG performance score of 0, 1, or 2. Exclusion Criteria: * The patient has bilirubin levels or aspartate transaminases (AST) levels within exclusionary ranges. * patient has serum creatinine concentrations within exclusionary ranges. * patient has an untreated or progressive infection. * patient has any physical or psychiatric condition that may compromise participation in the study. * has a history of venous or arterial thrombosis within 6 months. * use of hydroxyurea has been initiated or escalated in the month prior to screening. * has active gastrointestinal ulceration or bleeding. * patient has used an investigational drug within the past 30 days. * patient is being treated with anagrelide. * patient has previously taken CEP-701 (lestaurtinib). * patient has hypersensitivity to CEP-701 (lestaurtinib) or any component of CEP-701 (lestaurtinib). * patient has received interferon within the past 30 days.