Success for pacritinib in PERSIST-1 trial for myelofibrosis- CTI Biopharma + Baxter

CTI BioPharma Corp. and Baxter International Inc. announced positive top-line results for the primary endpoint from PERSIST-1, the randomized, controlled Phase III registration clinical trial examining pacritinib, a next generation oral JAK2/FLT3 multikinase inhibitor, for the treatment of patients with primary or secondary myelofibrosis. The PERSIST-1 trial met its primary endpoint in the intent-to-treat population with statistically significant activity observed in patients irrespective of their initial platelet count, including patients with very low platelet counts at study entry, a condition known as severe or life-threatening thrombocytopenia.

The primary endpoint of the trial was the proportion of patients achieving a 35 percent or greater reduction in spleen volume from baseline to Week 24 as measured by magnetic resonance imaging (MRI) or computerized tomography (CT) when compared with physician-specified best available therapy (BAT), excluding treatment with JAK2 inhibitors. The PERSIST-1 trial demonstrated that pacritinib treatment provided a clinically and statistically significant response rate (p = 0.0003) in spleen volume reduction in patients with myelofibrosis when compared to BAT. Importantly, the trial results also demonstrated a significant difference among patients with platelet counts of less than 100,000 per microliter and less than 50,000 per microliter, both subgroups that were stratified at randomization. The magnitude of treatment effect was consistent with previously reported Phase II results, with the greatest reduction observed among the sickest patients. The safety profile in the PERSIST-1 trial was consistent with prior Phase II trials.

Comment: Competitor is Jakafi (ruxolitinib), a dual JAK 1/2 inhibitor from Incyte and Novartis intended for myelofibrosis and recently approved in the USA. Despite the introduction of JAK2 inhibitors as effective therapies for patients with myelofibrosis, there remains a treatment gap for patients with disease-related or treatment emergent thrombocytopenia which pacritinib plans to fulfill.