Pacritinib: a new agent for the management of myelofibrosis?

INTRODUCTION

Myelofibrosis (MF) is a clonal haematological disease associated with recurrent somatic gene mutations (JAK2V617F, MPL, CALR) and constitutive activation of the Janus kinase (JAK)/Signal Transducer and Activator of Transcription pathway. MF is often characterised by debilitating symptoms and JAK inhibitors (JAKIs) have revolutionised available therapeutic options. Ruxolitinib, a JAK1 and 2 inhibitor, is the only currently approved agent. Several other JAKIs are undergoing evaluation in the clinical trial setting and Pacritinib , a novel JAK2 and FLT3 inhibitor, is at an advanced stage of investigation with recent completion of a Phase III trial and another ongoing.

AREAS COVERED

Within this article we focus on pacritinib, summarising the development, preclinical and up-to-date results from the Phase I - III trials. We present the most recent data on efficacy and safety and indirectly compare this novel JAKI with ruxolitinib.

EXPERT OPINION

The kinome array data for pacritinib suggests that it has a range of targets differing to those for ruxolitinib. Pacritinib appears to be an effective agent for the control of MF-related symptoms and splenomegaly with potentially fewer haematological side-effects when compared with ruxolitinib and seems a particularly promising agent for anaemic and thrombocytopenic patients. It is also an attractive drug for potential combination studies due to its good tolerability.

Evidence for Janus kinase (JAK) inhibitors for the prevention of major morbid events in patients with myeloproliferative neoplasms (MPNs)

A 69-year-old man presents with a Dynamic International Prognostic Scoring System (DIPSS) intermediate-risk 2 post polycythemia vera myelofibrosis with significant splenomegaly, 30 pound weight loss, constitutional symptoms, and 2% peripheral blood blasts. He has no other significant past medical history and no other major comorbid conditions. You are asked by the hematology fellow you are supervising whether or not treating this patient with a Janus kinase (JAK) inhibitor will decrease major morbid events.

Evidence for Janus kinase (JAK) inhibitors for the prevention of major morbid events in patients with myeloproliferative neoplasms (MPNs)

A 69-year-old man presents with a Dynamic International Prognostic Scoring System (DIPSS) intermediate-risk 2 post polycythemia vera myelofibrosis with significant splenomegaly, 30 pound weight loss, constitutional symptoms, and 2% peripheral blood blasts. He has no other significant past medical history and no other major comorbid conditions. You are asked by the hematology fellow you are supervising whether or not treating this patient with a Janus kinase (JAK) inhibitor will decrease major morbid events.