Pacritinib Reduces Spleen Enlargement, Symptom Burden in Patients With Myelofibrosis

The novel JAK1-sparing inhibitor pacritinib is effective at reducing spleen enlargement and disease burden in patients with cytopenic myelofibrosis (MF), according to a study that will be presented at the 2023 American Society of Clinical Oncology Annual Meeting.

JAK inhibitor therapy can reduce both splenomegaly and disease symptoms in patients with MF; however, dosing is often limited in individuals with cytopenic MF due to drug-induced exacerbations of cytopenias. Pacritinib can be used at full dose in patients with MF, regardless of where they stand on the cytopenic spectrum.

In this study, first author Prithviraj Bose and colleagues analyzed 276 patients who were treated with pacritinib in the PERSIST-1 and PERSIST-2 studies. The population of interest was stratified by baseline platelet (PLT; <100, ≥100×10⁹/L) and hemoglobin (HB; <8, 8 to <10, ≥10 g/dL) levels. The investigators then assessed depth of spleen volume response (SVR), modified total symptom score (TSS) response, patient global impression of change, and dose intensity.

The findings showed that 80% of patients had ≥10% SVR (SVR-10), over 75% had TSS-10, and nearly 80% reported reduced symptoms at week 24. Spleen reduction at week 24 occurred consistently across PLT and HB strata (84% to 93% and 86% to 90% of patients, respectively) the researchers noted. Moreover, SVR ≥35% occurred in 23% to 25% of patients across PLT strata and in 21% to 28% of patients across HB strata. The researchers further observed that symptom response was consistent across strata, with no loss of symptom burden reduction in patients with thrombocytopenia. Overall, the findings demonstrated that across all subgroups, at least 75% of patients reported symptoms were “improved” at week 24.

“Pacritinib demonstrates consistent efficacy for spleen and symptom response in patients with MF regardless of blood counts. This consistent effect may be related to [the unique kinome profile of pacritinib] and its ability to be delivered at full dose in patients regardless of cytopenias,” the researchers concluded.

Source: Bose P, Gagelmann N, McLornan D, et al. Consistency of pacritinib for spleen and symptom reduction in patients with myelofibrosis. Abstract #7068. Published for the 2023 ASCO Annual Meeting; June 2-6, 2023; Chicago, Illinois.