FDA Approves Pacritinib for Myelofibrosis and Thrombocytopenia

The FDA has granted accelerated approval to pacritinib (Vonjo) for adult patients with intermediate or high-risk primary or secondary (post-polycythemia vera or post-essential thrombocythemia) myelofibrosis with a platelet count below 50 × 10⁹/L.¹

Pacritinib becomes the first treatment approved to specifically address the needs of patients with cytopenic myelofibrosis, according to CTI BioPharma Corp, the developer of pacritinib.

"Today's approval of Vonjo establishes a new standard of care for myelofibrosis patients suffering from cytopenic myelofibrosis," John Mascarenhas, MD, associate professor of medicine, hematology, and medical oncology, at Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, New York, stated in a press release. "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 approval was based on data from the phase 3 PERSIST-1 (NCT01773187) and PERSIST-2 (NCT02055781) trials, and the phase 2 PAC203 trial.² In the PERSIST-2 trial, patients were administered pacritinib at a twice-daily dose of 200 mg. Twenty-nine percent of these patients showed a decrease in spleen volume of at least 30% vs 3% of those who received best available therapy (BAT), which included ruxolitinib (Jakafi). Further, 23% of patients had a reduction in total symptom scores of at least 50% compared 13% among patients administered BAT.

As part of the accelerated approval, CTI BioPharma will now be expected to demonstrate confirmatory findings of pacritinib in the phase 3 PACIFICA trial (NCT03165734), which is expected to have results in the middle of 2025.

The application for pacritinib was previously granted priority review designation, with an action date of November 30, 2021. However, the Prescription Drug User Fee Act action date was extended by 3 months to February 28, 2022.

"In the US, there are approximately 21,000 patients with myelofibrosis, two-thirds of which have cytopenias (thrombocytopenia or anemia), commonly resulting from the toxicity of other approved therapies,” said Adam R. Craig, MD, PhD, president and chief executive officer of CTI Biopharma. “Severe thrombocytopenia, defined as a blood platelet count below 50 × 10⁹/L, occurs in one-third of the overall myelofibrosis population, and has a particularly poor prognosis. With the approval of Vonjo, we are excited to now be able to offer a new therapy that is specifically approved for patients with cytopenic myelofibrosis.”

References

1. CTI BioPharma announces FDA accelerated approval of VONJO™ (pacritinib) for the treatment of adult patients with myelofibrosis and thrombocytopenia. CTI BioPharma Corp. News release. February 28, 2022. https://prn.to/33ZY8lU
2. CTI BioPharma announces completion of rolling submission of new drug application (NDA) for pacritinib in myelofibrosis patients with severe thrombocytopenia. News release. CTI BioPharma Corp. March 31, 2021. Accessed February 28, 2022. https://prn.to/3dlvNY2