A Phase III trial finds that Jakafi® (ruxolitinib) is more effective than standard therapy for patients with polycythemia vera (PV). These findings were published in the New England Journal of Medicine.
Polycythemia vera is a slow-growing type of blood cancer that belongs to a group of blood disorders called myeloproliferative neoplasms (MPN). In these disorders, the bone marrow cells that produce blood cells develop and function abnormally. In PV the bone marrow makes too many blood cells, particularly red blood cells. These excess cells thicken the blood and can cause complications, such as a risk of blood clots or bleeding. Without treatment, PV can be life threatening and can eventually progress to more serious blood cancers, such as myelofibrosis or acute leukemia. Effective treatment, however, can significantly decrease risks and complications.
The goal of therapy for PV is to reduce the thickness of the blood and prevent bleeding and clotting. Jakafi has proven effective in the therapy of PV, including patients with intolerance or resistance to Hydrea® (hydroxyurea), the most common first-line therapy for patients with high-risk PV. Jakafi works by inhibiting proteins that may play a role in the development of MPNs by causing the body to make the wrong number of blood cells (JAK1/JAK2 proteins).
Researchers conducted a Phase III study to compare Jakafi with standard therapies in patients who did not respond well to Hydrea. Patients included in the study were being treated with phlebotomy (a procedure to draw blood that is used to manage PV) and had an enlarged spleen (splenomegaly). They were divided into two study groups: one received Jakafi, and the other received standard therapy (which is often Hydrea). The researchers monitored hematocrit levels among the patients. Hematocrit is a measure of the proportion of total blood volume that is composed of red blood cells; because PV results in excessive levels of red blood cells, hematocrit is used to measure disease control. They also monitored spleen size.
At eight months, patients receiving Jakafi had significantly better disease control than those on standard therapy: 21% of Jakafi patients had disease control versus only 1% for standard therapy. Patients on Jakafi also had better hematocrit control (60% versus 20%) and had greater reduction in spleen size: 38% of Jakafi patients had at least a 35% reduction in spleen volume compared with only 1% on standard therapy. Furthermore, more patients on Jakafi experienced remission: 24% versus 9% of those in the standard-therapy group. More patients on Jakafi also experienced at least a 50% reduction in symptoms (49% versus 5%).
Side effects were similar between patients who received Jakafi and standard therapy. They included moderate anemia and thrombocytopenia (low platelet count).
These findings suggest that for patients with PV who don’t respond to or can’t tolerate Hydrea, Jakafi is more effective than standard treatment. Patients on Jakafi had better outcomes in three important areas: hematocrit control, reduction of spleen volume, and improved symptoms.
Reference: Vannucchi AM, Kiladjian JJ, Griesshammer M, et al. Ruxolitinib versus Standard Therapy for the Treatment of Polycythemia Vera. New England Journal of Medicine. 2015 Jan 29;372(5):426-35.
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