A JAK2/FLT3 inhibitor may be able to provide an alternative treatment option for patients with myelofibrosis and baseline thrombocytopenia, according to research presented in JAMA Oncology (online March 8, 2018; doi:10.1001/jamaoncol.2017.5818).
John Mascarenhas, MD, Tisch Cancer Institute (New York, NY), and colleagues compared the efficacy and safety for the JAK2 inhibitor pacritinib with that of best available therapy (BAT)—including ruxolitnib—in patients with myelofibrosis and thrombocytopenia.
The phase III randomized internal multicenter study enrolled 311 patients with myelofibrosis and platelet count 100x109/L or less for analysis. Crossover from BAT was allowed after week 24 or for progression of splenomegaly. Patients were randomized (1:1:1) to pacritinib 400 mg once daily, pacritinib 200 mg twice daily, or BAT.
Researchers noted that of the 311 patients included in the study, 149 of the patients had prior ruxolitinib. Ruxolitinib was the most common BAT used in the study, with 44 patients receiving this therapy vs 19 patients who received watchful-waiting only. The intention-to-treat efficacy population included 75 patients randomized to pacritinib once daily, 74 patients to pacritinib twice daily, and 72 patients to BAT.
The main endpoints of the study were rates of patients achieving 35% or more spleen volume reduction (SVR) and 50% or more reduction in total symptom score (TSS) at week 24. Efficacy analyses were performed on the intention-to-treat efficacy population, comprising all patients with a randomization date allowing for week 24 data.
Researchers reported pacritinib was more effective than BAT for 35% or more SVR and had a nonsignificantly greater rate of 50% or more reduction in TSS. Pacritinib twice daily led to significant improvements in both endpoints compared with BAT.
