US-based biopharmaceutical firm Incyte has reported results from RESPONSE, the first pivotal Phase III trial assessing a JAK1/JAK2 inhibitor for treatment of polycythemia vera (PV).
The trial showed that compared with best available therapy (BAT), ruxolitinib significantly improved hematocrit control without the need for phlebotomy and reduced at least 35% spleen size in patients with uncontrolled PV, those who are resistant to or intolerant of hydroxyurea (HU).
MD Anderson Cancer Center department of leukemia, division of cancer medicine professor Srdan Verstovsek said patients with advanced PV whose disease is not well-managed with existing therapies are at increased risk for thrombosis and suffer from multiple debilitating symptoms.
"Data from the RESPONSE trial demonstrated that treatment with ruxolitinib can consistently control hematocrit, reduce spleen size, and improve symptoms such as fatigue and itching," Verstovsek said.
"Importantly, there appears to be a lower rate of thrombosis in the ruxolitinib arm compared to best available therapy."
In the trial, 77% of patients treated with ruxolitinib versus 20% on best available therapy achieved one or both of the components of the primary endpoint.
A greater proportion of patients treated with ruxolitinib achieved the composite primary endpoint compared to BAT; 91% of patients in the ruxolitinib group achieving this endpoint maintained their response at week 48.
The company said that a greater proportion of patients in the ruxolitinib treatment arm had complete hematologic remission, a key secondary endpoint, when compared to the BAT arm.
About half of patients in the ruxolitinib group had at least a 50% improvement in symptom score, compared with 5% on best available therapy.
Incyte president and chief executive officer Hervé Hoppenot said one out of four patients with polycythemia vera remain uncontrolled, face a profound symptom burden and are at greater risk of cardiovascular complications such as stroke and heart attack.
"These Phase III data give us confidence that ruxolitinib has the potential to become an important new treatment option for patients with uncontrolled PV who are no longer responding to or are intolerant of hydroxyurea," Hoppenot said.
The results will support global regulatory filings scheduled to be done later in 2014, including submission to the US Food and Drug Administration (FDA) expected this month.
If approved, ruxolitinib would be the first JAK1/JAK2 inhibitor available for PV patients.
Jakafi is a prescription medicine approved by the FDA for the treatment of people with intermediate or high-risk myelofibrosis (MF), including primary MF, post-polycythemia vera MF and post-essential thrombocythemia MF.
The drug is marketed by Incyte in the US and by Novartis as Jakavi (ruxolitinib) outside the US.
Image: Blood smear from a patient with polycythemia vera. Photo: courtesy of Patho.