US FDA Approves JAK2 Inhibitor Pacritinib for Patients With Myelofibrosis

In February 2022, the US Food and Drug Administration (FDA) granted accelerated approval for pacritinib (Vonjo) capsules in patients with myelofibrosis and platelet levels below 50 x 10⁹/L.

In its phase 3 pivotal trial, PERSIST-2, pacritinib was more effective than best available therapy in patients with myelofibrosis and thrombocytopenia. PERSIST-2 randomized 311 patients with myelofibrosis and platelet levels below 100 × 10⁹/L to receive pacritinib 400 mg once daily, 200 mg twice daily, or standard care.

The researchers concluded that pacritinib significantly improved spleen volume and total symptom reductions compared with conventional therapy (P=.001). The twice-daily dose yielded the greatest improvements in hemoglobin and transfusion dependence and was established as the recommended dose. Notably, pacritinib was effective even among patients who had previously undergone treatment with ruxolitinib.

The FDA noted that, as a condition of the expedited approval, studies are ongoing to confirm pacritinib truly yields clinical benefit via its reduction of splenomegaly and symptoms in patients with intermediate- to high-risk primary or secondary myelofibrosis.

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