Hematologic response in patients with myelofibrosis treated with pacritinib in real-word clinical settings.

e23274 Background: Anemia is a major clinical burden for patients (pts) with myelofibrosis (MF) with a need for transfusions affecting quality of life and prognosis. Pacritinib (PAC) reduced transfusion requirements for pts with MF who were not transfusion-independent in the PERSIST-2 study. This may be attributed to PAC’s unique kinome profile as a JAK1-sparing inhibitor of JAK2/IRAK1/ACVR1, that can be delivered at full dose regardless of cytopenias. The current study evaluates hemoglobin (Hb) response and outcomes in patients (pts) with MF, including those with anemia treated with PAC in real-world settings. Methods: De-identified electronic health data from mostly community oncology practices were evaluated to select pts with MF treated with PAC between 6/2022 and 6/2024 with ≥90 days of follow-up from PAC initiation (index). Hb response was defined as an increase in Hb ≥1.5 g/dL. Hb and platelet counts (PLT) were described for pts with a response by baseline Hb levels: Hb < 8.0 g/dL, (severe anemia) and 8-10 g/dL (moderate anemia) and > 10 g/dL (mild/no anemia). Continuous variables were summarized using medians, and interquartile range (IQR), and categorical variables were reported as counts and percentages. Results: Of 148 PAC-treated pts with ≥90 days of follow-up and complete laboratory data, 65 (44%) achieved Hb response within a median of 40 days (IQR: 27, 84) from index, and 49 (33%) achieved a response within the first 90-days of index with a median of 33 days (22, 44) to response. Among pts with Hb response by day 90, 30 (61%) had severe anemia at index. In pts with Hb response by day 90, median Hb remained stable through day 180 in pts with severe, moderate, and mild/no anemia at index (Table). Median PLT counts improved from index through day 90 in pts with moderate and mild/no anemia at index and remained stable in those with severe anemia (Table). Median PLT counts remained stable through day 180 in pts with severe and moderate anemia (Table). Limited sample size prevented evaluation of PLT counts at day 180 for pts with mild/no anemia at index. Conclusions: Pts with MF including those with anemia treated with PAC in real-world clinical settings may experience improvement or stability in Hb. Pts with MF and severe or moderate anemia also experienced improvement or stability in PLT counts with PAC. These results suggest PAC may have clinical utility in pts with MF who have anemia. Impact of PAC in patients with MF and Hb response, by index Hb levels. Hb <8 g/dL Hb 8-10 g/dL Hb >10 g/dL N Median (IQR) N Median (IQR) N Median (IQR) Hb g/dL Index 30 7.0 (6.5, 7.5) 11 8.5 (8.2, 8.7) 8 11.0 (10.5, 11.6) Day 90 28 8.2 (7.4, 9.1) 7 9.0 (8.1, 10.0) 8 12.3 (12.1, 13.9) Day 180 28 8.2 (7.3, 9.1) 7 9.0 (8.1, 10.0) 7 12.1 (12.0, 13.5) PLT x10 9 /L Index 30 72 (33, 153) 11 34 (24, 86.5) 8 133 (105, 417) Day 90 26 70 (25, 167) 7 67 (26, 122) 8 244 (150, 435) Day 180 26 64.5 (29, 144.5) 7 52 (31, 101.5) 3 - Hb, hemoglobin; MF, myelofibrosis; PAC, pacritinib; - data not shown.