Results of a prospective, randomized, open-label phase 3 study of ruxolitinib (RUX) in polycythemia vera (PV) patients resistant to or intolerant of hydroxyurea (HU) the RESPONSE trial

SUMMARY:The FDA on December 4, 2014 approved JAKAFI® (Ruxolitinib) for the treatment of patients with Polycythemia Vera (P.Vera) who have had an inadequate response to or are intolerant of Hydroxyurea (HU). Polycythemia Vera is a clonal myeloproliferative neoplasm characterized by isolated Erythrocytosis in a majority of the patients, with the remaining demonstrating Leukocytosis and/or Thrombocytosis along with Erythrocytosis. Patients usually present with this disorder in their sixth decade and are often asymptomatic, with the diagnosis made incidentally on routine laboratory evaluation. About 30% of the patients however, may initially present with a thrombotic episode, whereas a small percentage of patients may present with disease related symptoms such as pruritus and fatigue. Overactivation of the JAK-STAT signal transduction pathway caused by V617F mutation, has been implicated in majority of the patients with P. Vera. This pathway normally is responsible for passing information from outside the cell through the cell membrane to the DNA in the nucleus, for gene transcription. Janus Kinase (JAK) family of tyrosine kinases are cytoplasmic proteins and include JAK1, JAK2, JAK3 and TYK2. JAK1 helps propagate the signaling of inflammatory cytokines whereas JAK2 is essential for growth and differentiation of hematopoietic stem cells. These tyrosine kinases mediate cell signaling by recruiting STAT’s (Signal Transducer and Activator of Transcription), with resulting modulation of gene expression. In patients with P. Vera, the aberrant myeloproliferation is the result of dysregulated JAK2-STAT signaling as well as excess production of inflammatory cytokines, associated with this abnormal signaling. JAK2 mutations such as JAK2 V617F are seen in approximately 95% of patients with P. Vera. The goals of therapy in P. Vera are to maintain the hematocrit at less than 45% and decrease the risk of thrombosis and bleeding. P. Vera is presently managed with periodic phlebotomies, cytoreductive therapy with oral antimetabolite, Hydroxyurea and antiplatelet agents such as low dose Aspirin. However, a significant number of patients on these therapies become intolerant or resistant to these treatments, leading to an increased risk of progression. JAKAFI® is a potent JAK1 and JAK2 inhibitor and exerts its mechanism of action by targeting and inhibiting the dysregulated JAK2-STAT signaling pathway. The RESPONSE trial is a phase III prospective randomized study in which patients with P. Vera, who were refractory or intolerant of Hydroxyurea were randomized to receive JAKAFI® 10 mg PO, BID (N=110) or Best Available Therapy (BAT), which consisted of investigator choice of monotherapy or observation only (N=112). Eligible patients were phlebotomy dependent and had splenomegaly (> 450 cubic cm). Patients receiving BAT were allowed to cross over to JAKAFI® group from week 32 onwards. The primary endpoint of this study (composite primary endpoint) was the proportion of patients whose hematocrit was controlled without phlebotomy and whose spleen volume was reduced by 35% or more from baseline, as assessed by MRI imaging at 32 weeks. Secondary endpoints included durable response, Complete Hematological Remission and safety. The primary analysis was conducted when all patients reached week 48 or discontinued therapy. The proportion of patients in the JAKAFI® group who achieved the composite primary endpoint was 21% compared to 1% in the BAT group (P < 0.0001) and 91% in the JAKAFI® group maintained their response at week 48. Seventy seven percent (77%) of the patients in the JAKAFI® group achieved at least one of the two major components of the composite primary endpoint. Put another way, 60% of the patients in the JAKAFI® arm were able to achieve the target hematocrit level in the absence of phlebotomy, compared to 20% in the BAT group. Reduction in the spleen volume by 35% or more was noted in 38% of the patients in the JAKAFI® group compared to 1% in the BAT group. Complete Hematological Remission defined as continuous hematocrit below 45%, as well as normal white blood cells and platelets counts, was achieved in 24% and 9% of patients in JAKAFI® and BAT group respectively (P=0.003). More patients assigned to JAKAFI® group also demonstrated 50% or more improvement in the Myeloproliferative Neoplasm Symptom Assessment Form (MPN-SAF) 14-item total symptom score, at week 32 compared to BAT (49% vs 5%). Thromboembolic events occurred in one patient assigned to the JAKAFI® group as compared to six patients in the BAT group. The authors concluded that JAKAFI® may represent a new option for treating high risk patients with Polycythemia Vera, who are refractory or intolerant of Hydroxyurea. JAKAFI® is superior to Best Available Therapy (BAT) in controlling hematocrit without phlebotomies as well as Splenic Volume. Further, JAKAFI® is also effective in improving P. Vera associated symptoms. Verstovsek S, Kiladjian J, Griesshammer M, et al. J Clin Oncol 32:5s, 2014 (suppl; abstr 7026)

JAKAFI® (Ruxolitinib)

The FDA on December 4, 2014 approved JAKAFI® for the treatment of patients with Polycythemia Vera (PV) who have had an inadequate response to or are intolerant of Hydroxyurea (HU). JAKAFI® is a product of Incyte Corporation.

Results of a prospective, randomized, open-label phase 3 study of ruxolitinib (RUX) in polycythemia vera (PV) patients resistant to or intolerant of hydroxyurea (HU) the RESPONSE trial

SUMMARY: Polycythemia Vera (P. Vera) is a clonal myeloproliferative neoplasm characterized by isolated Erythrocytosis in a majority of the patients, with the remaining demonstrating Erythrocytosis, Leukocytosis and/or Thrombocytosis along with Erythrocytosis. Patients usually present with this disorder in their sixth decade and are often asymptomatic, with the diagnosis made incidentally on routine laboratory evaluation. About 30% of the patients however, may initially present with a thrombotic episode, whereas a small percentage of patients may present with disease related symptoms such as pruritus and fatigue. Over activation of the JAK-STAT signal transduction pathway caused by V617F mutation, has been implicated in majority of the patients with P. Vera. This pathway normally is responsible for passing information from outside the cell through the cell membrane to the DNA in the nucleus for gene transcription. Janus Kinase (JAK) family of tyrosine kinases are cytoplasmic proteins and include JAK1, JAK2, JAK3 and TYK2. JAK1 helps propagate the signaling of inflammatory cytokines whereas JAK2 is essential for growth and differentiation of hematopoietic stem cells. These tyrosine kinases mediate cell signaling by recruiting STAT’s (Signal Transducer and Activator of Transcription), with resulting modulation of gene expression. In patients with P. Vera, the aberrant myeloproliferation is the result of dysregulated JAK2-STAT signaling as well as excess production of inflammatory cytokines associated with this abnormal signaling. JAK2 mutations such as JAK2 V617F are seen in approximately 95% of patients with P. Vera. The goals of therapy in P. Vera are to maintain the hematocrit at less than 45% and decrease the risk of thrombosis and bleeding. P. Vera is presently managed with periodic phlebotomies, cytoreductive therapy with oral antimetabolite, Hydroxyurea and antiplatelet agents such as low dose aspirin. However, a significant number of patients on these therapies become intolerant or resistant to these treatments, leading to an increased risk of progression. JAKAFI® is a potent JAK1 and JAK2 inhibitor and exerts its mechanism of action by targeting and inhibiting the dysregulated JAK2-STAT signaling pathway. The RESPONSE trial is a phase III prospective randomized study in which patients with P. Vera, who were refractory or intolerant of Hydroxyurea were randomized to receive JAKAFI® 10 mg PO, bid (N=110) or Best Available Therapy (BAT), which consisted of investigator choice of monotherapy or observation only (N=112). Eligible patients were phlebotomy dependent patients with splenomegaly (> 450 cubic cm). Patients receiving BAT were allowed to cross over to JAKAFI® group from week 32 onwards. The primary endpoint of this study (composite primary endpoint) was the proportion of patients whose hematocrit was controlled without phlebotomy and whose spleen volume was reduced by 35% or more from baseline, as assessed by MRI imaging at 32 weeks. Secondary endpoints included durable response, Complete Hematological Remission and safety. The primary analysis was conducted when all patients reached week 48 or discontinued therapy. The proportion of patients in the JAKAFI® group who achieved the composite primary endpoint was 21% compared to 1% in the BAT group (P < 0.0001). Seventy seven percent (77%) of the patients in the JAKAFI® group achieved at least one of the two major components of the composite primary endpoint. Put another way, 60% of the patients in the JAKAFI® arm were able to achieve the target hematocrit level in the absence of phlebotomy, compared to 20% in the BAT group. Reduction in the spleen volume by 35% or more was noted in 38% of the patients in the JAKAFI® group compared to 1% in the BAT group. Complete Hematological Remission defined as continuous hematocrit below 45%, as well as normal white blood cells and platelets counts, was achieved in 24% and 9% of patients in JAKAFI® and BAT group respectively (P=0.003). More patients assigned to JAKAFI® group also demonstrated 50% or more improvement in the Myeloproliferative Neoplasm Symptom Assessment Form (MPN-SAF) 14-item total symptom score, at week 32 compared to BAT (49% vs 5%). Thromboembolic events occurred in one patient assigned to the JAKAFI® group as compared to six patients in the BAT group. The authors concluded that JAKAFI® may represent a new option for treating high risk patients with Polycythemia Vera, who are refractory or intolerant of Hydroxyurea. Jakafi® is superior to Best Available Therapy (BAT) in controlling hematocrit without phlebotomies as well as Splenic Volume. Further, JAKAFI® is also effective in improving P. Vera associated symptoms. Verstovsek S, Kiladjian J, Griesshammer M, et al. J Clin Oncol 32:5s, 2014 (suppl; abstr 7026)

Cardiovascular Events and Intensity of Treatment in Polycythemia Vera

SUMMARY: The significance of maintaining a hematocrit less than 45% to prevent cardiovascular events, was evaluated in this randomized clinical study. Patients with JAK2-positive polycythemia vera (n=365) treated with phlebotomy, hydroxyurea, or both were randomized to receive either a more intensive treatment to maintain a target hematocrit of less than 45% (low-hematocrit group, n=182) or less intensive treatment to a target hematocrit of 45 to 50% (high-hematocrit group, n= 183). The primary end point was the time until death from cardiovascular events or major thrombotic episodes. The secondary end points included cardiovascular events, cardiovascular hospitalizations, incidence of cancer, progression to myelofibrosis, myelodysplasia or leukemia and hemorrhage. At a median follow-up of 31 months, the primary end point was recorded in 5 of 182 patients (2.7%) in the low-hematocrit group and 18 of 183 patients (9.8%) in the high-hematocrit group ( P=0.007). There were no significant differences in the secondary end points. The authors concluded that maintaining a lower hematocrit can lower the risk of cardiovascular death and major thrombosis. Marchioli R, Finazzi G, Specchia G, et al. N Engl J Med 2013; 368:22-33