A phase I, open-label, multi-center study of the JAK2 inhibitor AZD1480 in patients with myelofibrosis.

The anti-tumor activity of AZD1480, a potent, selective inhibitor of Janus-associated kinases 1 and 2, was demonstrated in preclinical models of myeloproliferative neoplasms. In a phase I clinical study, 35 patients with myelofibrosis received 2.5-70mg AZD1480 orally once daily (QD) or 10 or 15mg twice daily (BID) continuously during repeated 28-day cycles. Two patients experienced dose-limiting toxicities: one patient in the 2.5mg QD cohort had a grade 3 lung infiltration/acute pneumonia, and one patient receiving 50mg QD had grade 3 presyncope. Dosing was stopped at 70mg QD after the first patient experienced an adverse neurological event (AE) and evidence of low-grade neurological toxicity in patients on lower doses after the initial month of therapy became apparent. The most common AZD1480-related AEs were dizziness and anemia. AZD1480 was absorbed quickly and eliminated from the plasma rapidly, with a mean terminal half-life of 2.45-8.06h; accumulation was not observed after repeated daily dosing for 28 days. Four patients showed evidence of clinical improvement based on IWG-MRT 2006 criteria. AZD1480 was relatively well tolerated, however, low-grade, reversible neurological toxicity was therapy limiting and led to study termination.