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Pacritinib improves response rate, fails to reduce symptom score in high-risk myelofibrosis
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A phase 3 study designed to evaluate pacritinib for high-risk patients with myelofibrosis met one of its primary endpoints but failed to meet another, according to the agent’s manufacturer.
The randomized, controlled PERSIST-2 trial compared pacritinib (CTI BioPharma) — an investigational oral multikinase inhibitor — with physician-specified best available therapy, including the JAK2 inhibitor ruxolitinib (Jakafi, Incyte) for patients with myelofibrosis whose platelet counts were less than 100,000 per microliter.
The trial included 311 patients in a safety analysis who were randomly assigned 1:1:1 to 200 mg pacritinib twice daily, 400 mg pacritinib once daily or best available therapy. The efficacy analysis included 221 patients enrolled 24 weeks prior to the time the FDA imposed a clinical hold on studies that involved pacritinib.
Preliminary results showed the trial met one of its co-primary endpoints, as patients assigned pacritinib demonstrated a significant improvement in response rate in spleen volume reduction (P < .01). However, the trial did not meet its other co-primary endpoint of greater than 50% reduction in total symptom score.
“Unlike patients with myelofibrosis who have normal baseline platelet counts where median survival is reported at 88 months, we recently reported from our institution's experience that patients with severe thrombocytopenia had a median survival of about 14 months,” principal investigator Srdan Verstovsek, MD, PhD, director of the Clinical Research Center for Myeloproliferative Neoplasms at The University of Texas MD Anderson Cancer Center and a HemOnc Today Editorial Board member, said in a CTI BioPharma-issued press release. “These patients represent up to 30% of all myelofibrosis patients and an unmet medical need. Data from the PERSIST-2 prospective randomized, controlled trial is encouraging because we need an effective therapy to treat the most challenging patients with low platelet counts we see in our practice.”
The most common treatment-emergent adverse events associated with pacritinib included diarrhea, nausea and vomiting. Incidence of cardiac and bleeding adverse events, as well as overall mortality rates, were comparable between study arms.
Complete top-line results from PERSIST-2, along with additional data from ongoing analyses, will be submitted for presentation at an upcoming scientific meeting.
“Having analyzed data from two phase 3 trials with the only JAK inhibitor to be studied in severely thrombocytopenic patients, including patients on JAK2 therapy or those who failed prior JAK2, we are encouraged by pacritinib's clinical profile in this difficult-to-treat group of patients with myelofibrosis,” James A. Bianco, MD, president and CEO of CTI BioPharma, said in the press release. “We are grateful for the support and commitment of the investigators, our steering committee and, most importantly, all the patients who participated in PERSIST-2.”