Phase III safety and efficacy results for SB 1518 (pacritinib) in myelofibrosis- CTI Biopharma

CTI BioPharma has announced long-term safety and efficacy results from the pivotal Phase III PERSIST-1 trial evaluating SB 1518 (pacritinib) versus best available therapy, excluding treatment with JAK2 inhibitors (BAT), in patients with myelofibrosis. As previously reported, the PERSIST-1 trial met its primary endpoint in the intent-to-treat population with statistically significant reduction in spleen volume when compared to patients receiving BAT.

The results represent an update on the efficacy and safety for all patients regardless 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 most frequently occurring adverse events with pacritinib were gastrointestinal events and incidence decreased over time. For patients crossing over to receive pacritinib treatment (84 percent of BAT patients), less than 5 percent of patients had diarrhea with only one patient experiencing grade 3. Patients in the BAT arm that crossed over to receive pacritinib treatment had a similar rate of events as patients initially randomized to BAT or pacritinib.

A planned analysis of the study up to 72 weeks demonstrated treatment with pacritinib led to durable reductions in spleen volume and symptom burden, two key measures of disease control, in patients with myelofibrosis, including patients with low platelets at baseline (less than 50,000 per microliter and less than 100,000 per microliter). Patients who crossed over to pacritinib from BAT experienced similar reductions in spleen volume and symptom burden as patients initially randomized to pacritinib, including patients with low platelets. Data were presented the American Society of Clinical Oncology meeting.

Comment: Pacritinib may offer an advantage over other JAK inhibitors through effective treatment of symptoms while having less treatment-emergent thrombocytopenia and anemia than has been seen in currently approved and in-development JAK inhibitors.