CHICAGO—The JAK1/2 inhibitor ruxolitinib may be a “valuable new treatment option” for patients with polycythemia vera (PV) who cannot tolerate or are resistant to hydroxyurea, according to a speaker at the 2014 ASCO Annual Meeting.
Results of the phase 3 RESPONSE trial showed that ruxolitinib can reduce spleen size in these patients and improve hematocrit control without the need for phlebotomy.
And the drug was generally well-tolerated.
“Patients with PV may not have their disease controlled with existing therapies, increasing their risk for cardiovascular complications,” said Srdan Verstovsek, MD, PhD, of MD Anderson Cancer Center in Houston, Texas.
“In the RESPONSE trial, patients treated with ruxolitinib showed better disease control and improved symptom management compared to [patients who received] current therapies.”
Dr Verstovsek presented results from the trial at ASCO as abstract 7026. RESPONSE was funded by Incyte Corporation, the company developing ruxolitinib.
The study has enrolled 222 patients with PV that is resistant to or intolerant of hydroxyurea. Patients were randomized to receive either ruxolitinib at a starting dose of 10 mg twice-daily or best available therapy (BAT). The ruxolitinib dose was adjusted as needed throughout the study.
At week 32, 77% of patients on ruxolitinib and 20% on BAT achieved hematocrit control or spleen reduction.
The primary endpoint of the study was the proportion of patients whose hematocrit was controlled without phlebotomy from week 8 through 32 and whose spleen volume was reduced by 35% or more from baseline as assessed by imaging at 32 weeks.
Twenty-one percent of patients in the ruxolitinib arm achieved this endpoint, compared to 1% of patients in the BAT arm.
“Ninety-one percent of patients who achieved the primary end point had a confirmed response at 48 weeks,” Dr Verstovsek said.
He also noted that nearly half of ruxolitinib-treated patients had a 50% or greater reduction in debilitating PV symptoms, compared to 5% of those on BAT.
Patients treated with ruxolitinib also experienced a reduction in night sweats and itchiness. In addition, a greater proportion of patients in the ruxolitinib arm achieved complete hematologic response when compared to the BAT arm—24% and 9%, respectively.
Ruxolitinib was generally well-tolerated, Dr Verstovsek said, noting that 85% of patients were still receiving the drug at a median follow-up of 81 weeks.
However, 3.6% of patients on ruxolitinib discontinued treatment due to adverse events, compared to 1.8% of patients on BAT.
Most adverse events observed in the ruxolitinib arm were grade 1 or 2 and were consistent with those previously seen in ruxolitinib studies in PV and myelofibrosis.
Few patients developed grade 3 or 4 cytopenias. Within the first 32 weeks of treatment, grade 3 or 4 hematologic adverse events in the ruxolitinib treatment arm were anemia (1.8%) and thrombocytopenia (5.5%). Fewer patients treated with ruxolitinib experienced thromboembolic events when compared to those who received BAT.
The most common non-hematologic adverse events were headache, diarrhea, and fatigue, which were mainly grade 1 or 2. Dr Verstovsek noted that herpes zoster infection was higher in the ruxolitinib arm than in the BAT arm.
Ruxolitinib is currently approved in more than 60 countries for patients with myelofibrosis. Global regulatory filings for PV are underway based on the RESPONSE data.