CancerConnect News: A new drug called Jakafi® (ruxolitinib) appears to help patients with polycythemia vera (PV) maintain hematocrit control more effectively than best available therapy. These findings were presented at the 56th American Hematology Society Annual Meeting and Exposition, December 6–9, 2014, in San Francisco, California.
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 treatment for PV is to reduce the thickness of the blood and prevent bleeding and clotting. Jakafi has proven effective in the treatment of PV, including in patients with intolerance or resistance to Hydrea® (hydroxyurea), the most common first-line treatment 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).
A current Phase III study, the RESPONSE trial, is comparing outcomes between Jakafi and best available therapy in patients with PV who can’t tolerate Hydrea or are resistant to it. Participants have been assigned to either best available treatment or Jakafi. Best available therapy includes Hydrea, several other drugs, or no medication. In a primary analysis of RESPONSE outcomes, Jakafi more effectively improved clinical signs of disease (hematocrit control and at least a 35% reduction in spleen size) and symptoms in patients with PV. After eights months of study, patients on best available therapy who had not reached desired disease control were allowed to switch to treatment with Jakafi.
In this particular analysis, researchers used hematocrit control to measure the effectiveness of Jakafi as treatment for PV. 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. Specifically, with this analysis researchers assessed whether even patients who didn’t reach the trial’s defined level for hematocrit control after eight months of treatment could still reach hematocrit control with Jakafi.
The 222 patients included in the RESPONSE trial all had PV and were resistant or intolerant to Hydrea. They were divided into two treatment groups: 110 received Jakafi and 112 received best available therapy. The researchers measured hematocrit regularly throughout the first eight months and continued after the eight-month screening. The researchers also monitored the number of phlebotomy procedures (procedure to draw blood that is used to manage PV) needed to treat PV in both groups.
Jakafi appeared to more effectively help manage hematocrit levels than best available treatment, even among patients who at eight months had not reached the study’s defined levels for hematocrit control. At 12 months, 97% of patients receiving Jakafi were likely to have maintained hematocrit control; at 20 months, 87% of these patients were likely to have maintained hematocrit control. Patients receiving Jakafi also had a longer period before becoming eligible for phlebotomy: Jakafi patients weren’t eligible for a median of one year versus a median of just over five months for those on best available therapy. Patients who received Jakafi also had better control of symptoms overall that those on best available therapy, with greater improvements in tiredness, itching, and night sweats.
This analysis of findings from the RESPONSE trial indicates that Jakafi more effectively helps patients with PV maintain long-term hematocrit control than best available therapy. As more study data is released, Jakafi appears increasingly promising in the treatment of PV.
 Verstovse S, Kiladjian J-J, Mesa R, et al. Ruxolitinib. Efficacy By Hematocrit Control in Patients with Polycythemia Vera: An Analysis of the RESPONSE Trial. Program and Abstracts of 56th American Hematological Society Annual Meeting and Exposition; December 6–9, 2014; San Francisco, California. Abstract 3201.
 Study of Efficacy and Safety in Polycythemia Vera Subjects Who Are Resistant to or Intolerant of Hydroxyurea: JAK Inhibitor INC424 (INCB018424) Tablets Versus Best Available Care: (The RESPONSE Trial) ((RESPONSE)). ClinicalTrials.gov website. Available at: https://clinicaltrials.gov/ct2/show/NCT01243944. Accessed December 6, 2014.
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