Pacritinib at full dose demonstrates efficacy for spleen, symptom, and transfusion response among patients with myelofibrosis (MF) who have both thrombocytopenia and anemia, according to data presented at the 2024 American Society of Clinical Oncology (ASCO) meeting.

“Pacritinib is a JAK1-sparing inhibitor of JAK2/IRAK1/ACVR1 that has been studied at full dose in patients with MF regardless of baseline thrombocytopenia or anemia,” stated lead study author Pankit Vachhani, MD, O'Neal Comprehensive Cancer Center at UAB, Birmingham, Alabama, and colleagues.

Investigators included 46 patients who were treated with pacritinib at 200 mg twice daily and 47 patients who received best available therapy on PERSIST-2 with bicytopenia at baseline (platelet count <100 x10⁹/L and hemoglobin <10 g/dL). This group retrospectively analyzed for spleen volume reduction (SVR) ≥35%, total symptom score (TSS; version 2.0, excluding tiredness) reduction of ≥50%, Patient Global Impression of Change (PGIC), median dose intensity, and transfusion independence response (TI-R).

In addition, baseline characteristics were presented in the safety population (patients randomized ≥12 weeks prior to study end and treated), and efficacy was presented in the intention-to-treat efficacy population (patients randomized ≥22 weeks prior to end of study).

Study results demonstrated that among the patients who received pacritinib and those treated with best available therapy, the baseline characteristics were generally similar, respectively: median age (65 vs 68 years), platelet count (46 vs 46 x10⁹/L), and hemoglobin (8.4 vs 8.6 g/dL). A lower percentage of patients in the pacritinib arm than in the best available therapy arm were receiving red blood cell transfusions (59% vs. 77%) and had prior Janus kinase (JAK) inhibitor exposure (43% vs 55%). Furthermore, most patients treated with pacritinib were able to maintain full doses over time, with the median actual dose intensity for pacritinib measuring 400 mg/day.

Study authors noted 45% of patients in the best available therapy arm received ruxolitinib (median last total daily dose: 10 mg), and in the pacritinib arm, 20% of patients had SVR ≥35% compared to 0% in the other arm (P = .0054). Comparably, 32.5% of the patients receiving pacritinib had ≥50% reduction of TSS compared to 10.5% of patients in the best available therapy group (P = .0274).

The PGIC response (patient-reported symptoms “very much” or “much” improved) at week 24 was greater among those treated with pacritinib (30%) compared to best available therapy (13.2%; P = NS). It was concluded that, among the 27 patients on pacritinib and 36 on best available therapy who received red blood cell transfusions at baseline, 26% of patients on pacritinib and 8% of patients on best available therapy achieved transfusion independent response (P = .0838).

“These findings suggest [pacritinib] may be an effective option to address the unmet need for [patients] with MF and bicytopenias,” Dr Vachhani et al summarized.

Source:

Vachhani P, Gupta V, Palandri F, et al. Efficacy of pacritinib in patients with myelofibrosis who have both thrombocytopenia and anemia. Presented at the ASCO Annual Meeting. May 31–June 4, 2024; Chicago, IL. Abstract 6578