A Randomized, Open-Label, Multicenter, Phase 2 Study to Evaluate the Efficacy, Safety, and Pharmacokinetics of KRT-232 Compared with Ruxolitinib in Patients with Phlebotomy-Dependent Polycythemia Vera

Background:Polycythemia vera (PV) is a myeloproliferative neoplasm (MPN) characterized by clonal stem cell proliferation of the erythroid, myeloid, and megakaryocytic lines. The predominant clinical characteristic is an increase in red cell mass, resulting in hyperviscosity of the blood, which is responsible for most symptoms during early stages of disease. Disease progression typically results in symptomatic splenomegaly and severe constitutional symptoms, causing significant morbidity and a shortened life expectancy. Patients with PV may develop cardiovascular complications, myelofibrosis (MF), myelodysplasia, or acute myeloid leukemia (AML). Long-term (20-year) survival for PV is 18%, highlighting the poor long-term prognosis and need for additional therapies. Phlebotomy and low-dose aspirin are the standard of care for initial treatment; hydroxyurea (HU) remains the myelosuppressive agent of choice, despite the increased potential for leukemic transformation, estimated at 10% after 13 years of exposure. The Janus kinase (JAK) inhibitor ruxolitinib is approved in the US and Europe for the treatment of patients who have had an inadequate response to or are intolerant of HU. In clinical trials, ruxolitinib produced responses in 23% of patients, compared with <1% in patients receiving best available therapy (Verstovsek, et al. Haematologica. 2016). Despite this significant improvement, there remains a substantial unmet need for patients with PV who are resistant to or intolerant of HU.