Dr Bose on Spleen and Symptom Benefit With Pacritinib in Myelofibrosis

Prithviraj Bose, MD, associate professor, Department of Leukemia, Division of Cancer Medicine, The University of Texas MD Anderson Cancer Center, discusses key data on the ability of pacritinib (Vonjo) to reduce splenomegaly and disease symptoms in patients with myelofibrosis across the cytopenic spectrum.

In a study presented at the 2023 ASCO Annual Meeting, the dosing and efficacy of pacritinib by degree of baseline thrombocytopenia and anemia was assessed in patients with myelofibrosis who were treated with pacritinib in the phase 3 PERSIST-1 (NCT01773187) and PERSIST-2 (NCT02055781) trials.

Evaluable patients in these trials were stratified by both baseline thrombocytopenia and anemia. Patients were grouped by baseline platelet counts of less than or over 100 x 109/L, as well as hemoglobin levels less than 8 g/dL, 8 g/dL to less than 10 g/dL and greater than 10 g/dL. Depth of spleen volume response, total symptom score, Patient Global Impression of Change (PGIC), and dose intensity were evaluated in both groups.

Findings showed that pacritinib had consistent efficacy in patients regardless of their baseline blood counts. Patients across all baseline platelet and hemoglobin subgroups were able to continue pacritinib at 100% median dose intensity throughout the treatment course. Moreover, 21% to 28% of patients in the overall population achieved a 35% or greater reduction in spleen volume, 39% to 44% achieved a 25% or greater reduction, and 84% to 93% experienced any reduction. The depth of this effect at week 24 was consistent across all stratified subgroups.

Between 80% to 87.5% of patients in all cytopenia groups experienced any improvement in disease symptoms. Improvements in total symptom score were observed by week 12 and sustained through week 36 of treatment. Lastly, approximately 80% of patients across all blood count groups reported a clinical improvement in disease symptoms based on PGIC response, and about 50% reported improved symptoms at week 24.

It is hypothesized that this effect could be attributed to pacritinib’s unique mechanism of action as a JAK1-sparing inhibitor and its ability to be delivered at full dosage regardless of the degree of cytopenias.

Disclosures: Dr Bose reported serving as a consultant or in an advisory role for AbbVie, Bristol-Myers Squibb/Celgene, GlaxoSmithKline/Sierra Oncology, Karyopharm Therapeutics; he received honoraria from AbbVie, Blueprint Medicines, Bristol-Myers Squibb/Celgene, Cogent Biosciences, CTI BioPharma Corp, GlaxoSmithKline/Sierra Oncology, Incyte; Karyopharm Therapeutics, Novartis, PharmaEssentia; he received institutional research funding from Astellas Pharma, Blueprint Medicines, Bristol-Myers Squibb/Celgene, Cogent Biosciences, Constellation Pharmaceuticals, CTI BioPharma Corp, Disc Medicine, Incyte, Ionis Pharmaceuticals, Kartos Therapeutics, NS Pharma, Pfizer, Promedior, and Telios.