An Expanded Treatment Protocol study that provided expanded access of the FDA-approved ruxolitinib, which treats polycythemia vera (PV) in patients who are intolerant or resistant to hydoxyurea, affirmed the safety and efficacy findings of the trials used for approval.
Ruxolitinib is the first FDA-approved therapy for patients with polycythemia vera (PV) who are resistant or intolerant to hydroxyurea (HU), and further evaluation in a phase 3b Expanded Treatment Protocol (ETP) study found that ruxolitinib’s safety and efficacy is consistent with what was observed in the studies FDA used to approve the drug. The findings were published in Leukemia & Lymphoma.
“Hydroxyurea has been the mainstay of cytoreductive therapy for high-risk patients with PV; however, some patients show suboptimal response to HU,” the authors explained. “It has been associated with frequent side effects including mucocutaneous toxicity and leukemogenic potential. Around one-fourth of the patients on HU therapy become resistant or intolerant, per [2018 European LeukemiaNet]-defined criteria.”
The phase 3b study was conducted among patients with PV who were resistant or intolerant of HU, had no other treatments available, and were ineligible for an ongoing trial. The trial provided early access to ruxolitinib and appraised the safety of the drug.
The study included 161 patients; all but 1 patient had received HU prior to the trial. The median duration of treatment was 25.1 weeks. The patients started the trial with a dose of 10 mg twice daily. They had visits every 4 weeks until week 24, after which they had visits scheduled every 12 weeks. Patients continued on ruxolitinib until disease progression, unacceptable toxicity, death, consent withdrawal, or discontinuation for any other reason.
In 8.7% of patients in the study, adverse events (AEs) leading to the discontinuation of treatment were reported. In 37.9% of patients, AEs led to dose adjustment/interruption. In the study population, more than half (54%) had discontinued prior therapy with HU because of AEs.
The most common hematologic AEs were anemia (31.8%), thrombocytosis (10.0%), and thrombocytopenia (7.3%). Headache (24.5%) and diarrhea (14.5%) were the most common nonhematologic AEs.
By week 24, 45.3% of the patients had achieved hematocrit control and 18.0% had blood count remission. More than three-fourths (76.7%) of patients achieved 100% splenic reduction at any time during the study, and 86.7% achieved 50% reduction in spleen length from baseline at any time during the study.
The authors concluded that the findings of the ETP were similar to those reported in the RESPONSE studies that FDA used to approve ruxolitinib, further validating the use of the drug in patients who are resistant or intolerant to HU.
“Taken together, these results along with the conclusions derived from the RESPONSE studies underline ruxolitinib as an alternative treatment option for the patients with inadequately controlled PV, an unmet medical need,” the authors wrote.
Foltz L, Pica GM, Zerazhi H, et al. Safety and efficacy findings from the open-label, multicenter, phase 3b, expanded treatment protocol study of ruxolitinib for treatment of patients with polycythemia vera who are resistant/intolerant to hydroxyurea and for whom no alternative treatments are available [published online July 30, 2019]. Leuk Lymphoma. doi: 10.1080/10428194.2019.1636985.