Incyte has started dosing patients in a Phase II clinical trial of ruxolitinib (Jakafi) in patients with essential thrombocythemia (ET) and resistant to or intolerant of hydroxyurea (HU).

Ruxolitinib is an inhibitor of JAK1/JAK2 and is approved by the US Food and Drug Administration (FDA) for treating polycythemia vera (PV).

The randomised, double-blind, cross-over, double-dummy Phase II trial is designed to assess the safety and efficacy of ruxolitinib in around 120 subjects aged 18 years and above.

During the treatment period, an oral twice-daily dose of ruxolitinib will be compared to a 1mg oral dose of anagrelide.

Incyte chief medical officer Steven Stein said: “We are pleased to treat the first patient in our pivotal trial evaluating ruxolitinib as a treatment for ET, a rare blood cancer that can lead to life-threatening complications.

“Advancing this trial to help address the needs of higher-risk patients with ET.”

“We look forward to building on the clinical evidence for ruxolitinib and to advancing this trial to help address the needs of higher-risk patients with ET, who are resistant to or intolerant of HU and currently have limited treatment options.”

The trial’s primary endpoint is the proportion of subjects achieving platelet and white blood cell (WBC) control over one year of follow-up.

Additionally, the trial will monitor key secondary endpoints of safety and tolerability measured by adverse events, along with the proportion of participants experiencing complete or partial remission as per European LeukemiaNet response criteria.

It is estimated that the pivotal trial will be completed in 2020.