Nilotinib, an orally bioavailable, selective Bcr-Abl tyrosine kinase inhibitor, is 30-fold more potent than imatinib in pre-clinical models, and overcomes most imatinib resistant BCR-ABL mutations. In this phase 2 open-label study, 400 mg nilotinib was administered orally twice daily to 280 patients with Philadelphia chromosome–positive (Ph⁺) chronic myeloid leukemia in chronic phase (CML-CP) after imatinib failure or intolerance. Patients had at least 6 months of follow-up and were evaluated for hematologic and cytogenetic responses, as well as for safety and overall survival. At 6 months, the rate of major cytogenetic response (Ph ≤ 35%) was 48%: complete (Ph = 0%) in 31%, and partial (Ph = 1%-35%) in 16%. The estimated survival at 12 months was 95%. Nilotinib was effective in patients harboring BCR-ABL mutations associated with imatinib resistance (except T315I), and also in patients with a resistance mechanism independent of BCR-ABL mutations. Adverse events were mostly mild to moderate, and there was minimal cross-intolerance with imatinib. Grades 3 to 4 neutropenia and thrombocytopenia were observed in 29% of patients; pleural or pericardial effusions were observed in 1% (none were severe). In summary, nilotinib is highly active and safe in patients with CML-CP after imatinib failure or intolerance. This clinical trial is registered at http://clinicaltrials.gov as ID no. NCT00109707.

The JAK-STAT signaling pathway plays a central role in signal transduction in hematopoietic cells, as well as in cells of the immune system. The occurrence in most patients affected by myeloproliferative neoplasms (MPNs) of driver mutations resulting in the constitutive activation of JAK2-dependent signaling identified the deregulated JAK-STAT signal transduction pathway as the major pathogenic mechanism of MPNs. It also prompted the development of targeted drugs for MPNs. Ruxolitinib is a potent and selective oral inhibitor of both JAK2 and JAK1 protein kinases. Its use in patients with myelofibrosis is associated with a substantial reduction in spleen volume, attenuation of symptoms and decreased mortality. With growing clinical experience, concerns about infectious complications, and increased risk of B-cell lymphoma, presumably caused by the effects of JAK1/2 inhibition on immune response and immunosurveillance, have been raised. Evidence shows that ruxolitinib exerts potent anti-inflammatory and immunosuppressive effects. Cellular targets of ruxolitinib include various components of both the innate and adaptive immune system, such as natural killer cells, dendritic cells, T helper, and regulatory T cells. On the other hand, immunomodulatory properties have proven beneficial in some instances, as highlighted by the successful use of ruxolitinib in corticosteroid-resistant graft vs. host disease. The objective of this article is to provide an overview of published evidence addressing the key question of the mechanisms underlying ruxolitinib-induced immunosuppression.

Nilotinib has a higher binding affinity and selectivity for BCR-ABL with respect to imatinib and is an effective treatment of chronic myeloid leukemia (CML) after imatinib failure. In a phase 2 study, 73 early chronic-phase, untreated, Ph+ CML patients, received nilotinib at a dose of 400 mg twice daily. The primary endpoint was the complete cytogenetic response (CCgR) rate at 1 year. With a median follow-up of 15 months, the CCgR rate at 1 year was 96%, and the major molecular response rate 85%. Responses were rapid, with 78% CCgR and 52% major molecular response at 3 months. During the first year, the treatment was interrupted at least once in 38 patients (52%). The mean daily dose ranged between 600 and 800 mg in 74% of patients, 400 and 599 mg in 18% of patients, and was less than 400 mg in 8% of patients. Dose interruptions were mainly due to nonhematologic and biochemical side effects. Myelosuppression was irrelevant. One patient progressed to blastic crisis after 6 months; one went off-treatment for lipase increase grade 4 (no pancreatitis). Nilotinib is safe and very active in early chronic-phase CML. These data support a role for nilotinib for the frontline treatment of CML. This study was registered at ClinicalTrials.gov as NCT00481052.

Imatinib mesylate (IM), 400 mg daily, is the standard treatment of Philadelphia-positive (Ph⁺) chronic myeloid leukemia (CML). Preclinical data and results of single-arm studies raised the suggestion that better results could be achieved with a higher dose. To investigate whether the systematic use of a higher dose of IM could lead to better results, 216 patients with Ph⁺ CML at high risk (HR) according to the Sokal index were randomly assigned to receive IM 800 mg or 400 mg daily, as front-line therapy, for at least 1 year. The CCgR rate at 1 year was 64% and 58% for the high-dose arm and for the standard-dose arm, respectively (P = .435). No differences were detectable in the CgR at 3 and 6 months, in the molecular response rate at any time, as well as in the rate of other events. Twenty-four (94%) of 25 patients who could tolerate the full 800-mg dose achieved a CCgR, and only 4 (23%) of 17 patients who could tolerate less than 350 mg achieved a CCgR. This study does not support the extensive use of high-dose IM (800 mg daily) front-line in all CML HR patients. This trial was registered at www.clinicaltrials.gov as #NCT00514488.