Experimental Rare Blood Cancer Drug Superior to Standard Therapy

Phase 3 trial for polycythemia vera drug significantly improved hematocrit control without the need for phlebotomy.

An experimental treatment for a rare form of blood cancer was found to produce superior results compared with the standard therapy in a recent phase 3 trial.

Ruxolitinib (Jakavi), manufactured by Novartis, was found to significantly improve hematocrit control without the need for phlebotomy in patients with polycythemia vera (PV). The drug also decreased spleen size in PV patients who previously had an inadequate response to, or unacceptable side effects from, hydroxyurea as defined by criteria set by the modified European LeukemiaNet (ELN).

The chronic and incurable form of blood cancer causes overproduction of blood cells, which can lead to serious cardiovascular complications, such as stroke and heart attack. Approximately 25% of PV patients either developed resistance to, or intolerance of, hydroxyurea.

These patients are considered to have uncontrolled disease typically defined by hematocrit levels that rise to greater than 45% and elevated white blood cell count and/or platelet count, which can be accompanied by adverse symptoms and/or an enlarged spleen. An elevated white blood cell count and hematocrit are associated with a greater risk of developing blood clots.

Hematocrit control and reduced spleen size are key measures of therapy response in PV patients.

"A key challenge in treating patients with PV is the development of resistance or intolerance to currently available therapies such as hydroxyurea, which leaves us with very limited alternative treatment options to effectively manage the disease," said study lead Alessandro M. Vannucchi, MD, in a press release. "This study indicates that ruxolitinib may represent an important advance for this population of patients with PV, a disease that can lead to serious complications and difficult daily symptoms."

In the trial, 49% of patients in the ruxolitinib group experienced a 50% or greater improvement in PV-related symptoms compared with 5% of patients treated with standard therapy. Patients treated with ruxolitinib also experienced an approximately 99% reduction in night sweats and itchiness compared with 95% in standard therapy.

By week 32 of the trial, 77% of patients in the ruxolitinib group achieved one or both components of the primary endpoint for hematocrit control, which was volume percentage of red blood cells in whole blood without the use of phlebotomy or reduced spleen size compared with 20% of patients in the standard therapy group.

A total of 21% of patients in the ruxolitinib group achieved the composite primary endpoint compared with 1% of patients on standard therapy, while 91% of patients treated with ruxolitinib maintained response at week 48.

Additionally, 24% of patients treated with ruxolitinib achieved complete hematologic remission as defined by modified ELN criteria compared with 9% of patients in the standard therapy group. One patient treated with ruxolitinib experienced a thromboembolic event compared with 6 patients within the first 32 weeks.