On February 28, 2022, the FDA accelerated the approval of pacritinib (Vonjo; CTI BioPharma), a kinase inhibitor, for the treatment of adult patients with intermediate- or high-risk primary or secondary (postpolycythemia vera or postessential thrombocythemia) myelofibrosis with a platelet count below 50 × 109/L. The FDA granted pacritinib priority review, fast track designation, and orphan drug designation for this indication.
“Today’s approval of Vonjo establishes a new standard of care for myelofibrosis patients suffering from cytopenic myelofibrosis,” said John Mascarenhas, MD, Associate Professor, Medicine, Hematology and Medical Oncology, Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, New York City. “Myelofibrosis with severe thrombocytopenia, defined as blood platelet counts below 50 × 109/L, has been shown to result in poor survival outcomes coupled with debilitating symptoms. Limited treatment options have rendered this disease as an area of urgent unmet medical need. I am pleased to see that a new, efficacious, and safe treatment option is now available for these patients.”
The FDA based its approval on efficacy results from the phase 3 PERSIST-2 clinical trial that included 63 patients with intermediate- or high-risk primary or secondary myelofibrosis and low platelet counts who received pacritinib 200 mg twice daily or standard therapy. Efficacy was determined based on the proportion of patients who had ≥35% spleen volume reduction from baseline to week 24. Nine (29%) patients in the pacritinib arm had a ≥35% reduction in spleen volume compared with 1 (3%) patient in the standard therapy arm.
The most common (≥20%) adverse reactions are diarrhea, thrombocytopenia, nausea, anemia, and peripheral edema. The most common (≥3%) serious adverse reactions are anemia, thrombocytopenia, pneumonia, cardiac failure, disease progression, pyrexia, and squamous-cell carcinoma of the skin. Patients must not use pacritinib if they are also taking certain other medications, such as strong CYP3A4 inhibitors or inducers.
As part of the accelerated approval, the manufacturer of pacritinib is required to describe a clinical benefit in a confirmatory trial. To fulfill this postapproval requirement, it plans to complete the PACIFICA trial, with expected results in mid-2025.
