ASXL1 mutation and leukocytosis undermine spleen response to pacritinib in myelofibrosis

ASXL1 mutation and leukocytosis (WBC >15 x 109/L) were found to be independently associated with inferior spleen response to pacritinib, in both patients with JAK inhibitor–naïve myelofibrosis and those with JAK inhibitor–exposed disease, according to data presented during the 2023 American Society of Hematology Annual Meeting. Spleen response was more likely to occur in patients without ASXL1 mutation (61% vs 10%; p=0.006), those with leukocyte count <15 x 10 (9)/L (55% vs 0%; p=0.005), and in JAK inhibitor–naïve vs previously exposed cases (75% vs 30%; p=0.03).