Patients with polycythemia vera (PV) who begin treatment with best available therapy and then switch to treatment with Jakafi® (ruxolitinib) experience improved outcomes. These findings were presented at the 56th American Hematological 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. The most common first-line treatment for patients with high-risk PV is chemotherapy with Hydrea; this is aimed at reducing the number of red blood cells made by the bone marrow, as well as excess levels of other blood cell types. Some patients, however, become intolerant of or resistant to Hydrea. Jakafi is another agent that’s proven effective in the treatment of PV, including in patients with intolerance of or resistance to Hydrea. 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 were assigned to either best available treatment or Jakafi. Best available therapy included Hydrea, several other drugs, or no medication.
Patients who initially received best available therapy were allowed to switch to Jakafi after eight months on the study. They were allowed to cross over to Jakafi at this time if their hematocrit levels (proportion of total blood volume composed of red blood cells) had not been controlled and their spleen size hadn’t been reduced by at least 35% or if disease had progressed.
According to these primary results from RESPONSE, Jakafi appears to more effectively reduce clinical signs of disease (control of hematocrit and spleen volume) and symptoms of PV than best available therapy.
The researchers measured hematocrit regularly throughout the first eight months. After eight months, hematocrit was measured periodically for another eight months. Spleen size was also measured regularly, using MRI (magnetic resonance imaging). 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.
At eight months, most (84%) of the patients receiving best available therapy switched over the Jakafi. This means that the majority of patients in the best available therapy group did not have acceptable disease control (hematocrit control or enough reduction in spleen size) at this point: 77% of those receiving Jakafi reached hematocrit control from week 8 to 32 and/or at least a 35% reduction in spleen volume or both compared with 20% on best available therapy.
The superior effectiveness of Jakafi was also measurable in phlebotomy records: at eight months only 25% of patients on best available therapy did not need a phlebotomy compared with 74% of those who started on Jakafi. More patients initially receiving Jakafi also had reduction in spleen size: 73% versus 49% for best available therapy.
According to results of the RESPONSE trial, patients with PV who switch to Jakafi after receiving best available treatment experience better outcomes than with original treatment. These findings add to increasing evidence suggesting that Jakafi is a promising treatment for patients with PV.
Reference: Kiladjian J-J, Vannucchi AM, Griesshammer M, et al. Clinical Benefit of Ruxolitinib Treatment after Crossover from Best Available Therapy in Patients with Polycythemia Vera: Analysis of the RESPONSE Trial. Programs and Abstracts of 56th American Hematological Society Annual Meeting and Exposition; December 6–9, 2014; San Francisco, California. Abstract 3181.
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