FDA approves Vonjo for adults with myelofibrosis, thrombocytopenia
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The FDA granted accelerated approval to pacritinib for treatment of adults with myelofibrosis and thrombocytopenia.
The approval applies to use of the agent by patients with intermediate- or high-risk primary or secondary myelofibrosis with a platelet count less than 50 x 109/L.
Pacritinib (Vonjo, CTI BioPharma) — an oral kinase inhibitor with specificity for JAK2, IRAK1 and CSF1R — is the first approved therapy specifically to address the needs of cytopenic adults with myelofibrosis.
Approximately one-third of patients with myelofibrosis develop severe thrombocytopenia, defined as blood platelet counts less than 50 x 109/L.
Thrombocytopenia is associated with underlying disease; however, it also can result from treatment with ruxolitinib (Jakafi, Incyte), a Janus kinase inhibitor approved for myelofibrosis. This can lead to treatment discontinuation. Survival for patients who discontinue ruxolitinib averages 7 to 14 months.
"[This] approval of Vonjo establishes a new standard of care for [patients with myelofibrosis] suffering from cytopenic myelofibrosis," John Mascarenhas, MD, associate professor of medicine, hematology and medical oncology at Tisch Cancer Institute and Icahn School of Medicine at Mount Sinai, said in a CTI BioPharma-issued press release. “Myelofibrosis with severe thrombocytopenia ... 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 approval on results of the phase 3 PERSIST-2 study, which included patients with myelofibrosis who had platelet counts of 100 x 109/L or less.
Researchers randomly assigned patients 1:1:1 to 200 mg pacritinib twice daily, 400 mg pacritinib once daily or best available therapy. Study protocol allowed patients who had received prior JAK2 inhibitor therapy to enroll.
In the subgroup of patients with baseline platelet counts below 50 × 109/L, a higher percentage of patients assigned 200 mg pacritinib twice daily than best available therapy demonstrated reduction in spleen volume of at least 35% (29% vs. 3%).
The most common adverse events reported among patients who received the 200-mg twice-daily dose included diarrhea, thrombocytopenia, nausea, anemia and peripheral edema. The most frequent serious adverse reactions included anemia, thrombocytopenia, pneumonia, cardiac failure, disease progression, pyrexia and cutaneous squamous cell.
The accelerated approval requires CTI BioPharma to show clinical benefit with pacritinib in a confirmatory trial. Results of this trial — PACIFICA — are expected in 2025.
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