Myelofibrosis

June 22, 2015

CTI BioPharma and Baxter International reported results from a randomized (2:1), open-label, multinational, phase III trial of pacritinib for myelofibrosis. The trial met its primary endpoint of spleen volume reduction (35% or greater from baseline to week 24 by MRI/CT scan) in the intent-to-treat population (ITT). These results included patients with severe or life-threatening thrombocytopenia. Data show that when measuring the volume of spleen reduction, the greatest difference in treatment arms was observed in evaluable patients with the lowest platelet counts (<50,000/uL platelets) (33.3% with pacritinib v. 0% with BAT) (p=0.037). When measuring the secondary endpoint (the proportion of patients with a 50% or greater reduction in Total Symptom Score (TSS) from baseline to week 24), patients treated with pacritinib experienced greater improvement in their symptoms when compared to best available therapy (BAT), regardless of their baseline platelet counts (ITT patient population: 24.5% of pacritinib-treated patients v. 6.5% of BAT-treated patients) (p<0.0001); Evaluable patient population: 40.9% of pacritinib-treated patients v. 9.9% of BAT-treated patients) (p<0.0001). 25% of patients treated with pacritinib who were severely anemic and transfusion dependent requiring at least six units of blood in the 90 days prior to study entry became transfusion independent, compared to zero patients treated with BAT (p<0.05). Among patients with the lowest baseline platelets (<50,000/uL) who received treatment with pacritinib, a significant increase in platelet counts was observed over time compared to BAT (p=0.003) with a 35% increase in platelet counts from baseline to week 24. The PERSIST clinical trials are intended to support an NDA to the FDA. In August 2014, pacritinib was granted Fast Track designation by the FDA for the treatment of intermediate and high risk myelofibrosis

March 23, 2015

CTI BioPharma and Baxter International released results of a phase III study of pacritinib for primary or secondary myelofibrosis. The randomized (2:1), open-label, multinational trial enrolled 327 patients and 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 physician-specified best available therapy (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 (platelet counts <50,000 per microliter). Among 50 patients who were red blood cell (RBC) transfusion dependent at study entry (six units of RBC over 90 days pre-entry), pacritinib therapy resulted in a clinically meaningful percentage of patients becoming transfusion independent compared to BAT. 79% of patients in the BAT arm of the study crossed over to pacritinib therapy. The safety profile was consistent with prior phase II trials. The PERSIST clinical trials are intended to support an NDA to the FDA.

July 8, 2013

Cell Therapeutics released results from a phase I/II trial of pacritinib for the treatment of myelofibrosis. The study enrolled 191 patients treated for myeloid, myelofibrosis or lymphoid malignancies. Of those with myeloid disorders, 44% had baseline platelet counts <100,000/μl. Pacritinib was dosed from 100mg to 600mg daily during phase I and 400mg during phase II. The median dose delivered was 98% of intended. The median treatment duration was 306 days for those with myeloid disorders and 90.5 days for lymphoid disorders. Most patients had no decline in hemoglobin or platelet count. Of the 30 patients with myeloid disorder with baseline platelet counts <50,000/μL from phase I and II studies, the median decline in platelet count observed was 3,000/μL. In the 11 patients with myelofibrosis with baseline platelet counts <50,000/μL enrolled in phase II studies, no dose reduction was required for worsening thrombocytopenia. Pacritinib is currently being evaluated in a randomized, phase III clinical trial.

Related Medical Areas