Dasatinib induces notable hematologic and cytogenetic responses in chronic-phase chronic myeloid leukemia after failure of imatinib therapy

Chronic myeloid leukemia: state of the art in 2012

The prognosis of Philadelphia positive (Ph+) chronic myeloid leukemia (CML) has been revolutionized since the discovery of the pathogenetic role of BCR-ABL and the invention of tyrosine kinase inhibitors (TKIs). With a follow-up of 8 years, patients had an OS of 85 % and, with second generation TKIs, dasatinib and nilotinib, almost 50 % of the resistant patients gained a remission with an OS over 90 % at 2 years. Currently the challenge is preventing resistance leading to progression to advance phases that have still few chances of effective treatment. Another objective, derived from the needs of our patients, beside the pride of the scientist, is the discontinuation of the treatment. Second generations TKIs applied to the first line setting seem to be a good option either to avoid progression and to achieve deeper rates of molecular response, necessary for the cure.

Dasatinib inhibits CXCR4 signaling in chronic lymphocytic leukaemia cells and impairs migration towards CXCL12

Chemokines and their ligands play a critical role in enabling chronic lymphocytic leukaemia (CLL) cells access to protective microenvironmental niches within tissues, ultimately resulting in chemoresistance and relapse: disruption of these signaling pathways has become a novel therapeutic approach in CLL. The tyrosine kinase inhibitor dasatinib inhibits migration of several cell lines from solid-organ tumours, but effects on CLL cells have not been reported. We studied the effect of clinically achievable concentrations of dasatinib on signaling induced by the chemokine CXCL12 through its' receptor CXCR4, which is highly expressed on CLL cells. Dasatinib pre-treatment inhibited Akt and ERK phosphorylation in CLL cells upon stimulation with CXCL12. Dasatinib also significantly diminished the rapid increase in actin polymerisation observed in CLL cells following CXCL12 stimulation. Moreover, the drug significantly inhibited chemotaxis in a transwell assay, and reduced the percentage of cells able to migrate beneath a CXCL12-expressing murine stromal cell line. Dasatinib also abrogated the anti-apoptotic effect of prolonged CXCL12 stimulation on cultured CLL cells. These data suggest that dasatinib, akin to other small molecule kinase inhibitors targeting the B-cell receptor signaling pathway, may redistribute CLL cells from protective tissue niches to the peripheral blood, and support the investigation of dasatinib in combination strategies.

Monitoring and switching patterns of patients with chronic myeloid leukemia treated with imatinib in community settings: a chart review analysis

OBJECTIVES

Monitoring treatment response is an integral part of chronic myeloid leukemia (CML) treatment. The guidelines recommend regular monitoring using standard methods (e.g., real-time quantitative polymerase chain reaction based on the international scale for molecular response) and treatment adjustment when failure is detected among patients treated with imatinib. The objective of this study was to assess the real-world monitoring and therapy adjustment in this patient population in the US.

METHODS

Twenty-nine physicians from community practices across the US participated in an online chart review. Adult patients with chronic phase CML who initiated imatinib as first-line therapy during 2006-2010 were selected. Information was collected up to 36 months after imatinib initiation, including response monitoring, response status, and therapy adjustment upon treatment failure.

RESULTS

The study included 297 eligible patients. By 18 months, 47% of patients had received cytogenetic response assessment continuously as recommended by the guidelines. The corresponding proportion was 39% for continuous molecular response assessment. Among patients who experienced treatment failure by 18 months, only 14%-38% of patients switched to a second-generation tyrosine kinase inhibitor as recommended by the National Comprehensive Cancer Network and the European Leukemia Net guidelines.

LIMITATIONS

Major limitations included limited generalizability and the inability to accurately assess molecular response due to the variations in testing methods during the study period.

CONCLUSIONS

Based on the guidelines, the rates of treatment monitoring and switching upon failure were low, demonstrating the need for improvement in CML care in community settings in the US.

Managing chronic myeloid leukemia patients intolerant to tyrosine kinase inhibitor therapy

The outcomes for patients with chronic myeloid leukemia have improved dramatically with the development and availability of BCR-ABL1 tyrosine kinase inhibitors (TKIs) over the past decade. TKI therapy has a superior safety profile compared with the previous standard of care, interferon-α, and most adverse events (AEs) observed with front-line and second-line TKI treatment are managed with supportive care. However, some patients are intolerant to TKI therapy and experience AEs that cannot be managed through dose reduction or symptomatic treatment. Careful management of AEs helps patients to remain adherent with treatment and increases their chances for successful outcomes. Proactive vigilance for potential AEs and treatment strategies that reduce symptom burden will help to minimize patient intolerance. This review discusses the most common AEs associated with intolerance to TKI therapy and treatment strategies to help manage patients at risk for or experiencing these events.

Pharmacokinetic-pharmacodynamic relationship of bosutinib in patients with chronic phase chronic myeloid leukemia

PURPOSE

Bosutinib is an orally active, dual Src/Abl tyrosine kinase inhibitor that has demonstrated manageable safety and high response rates in patients with chronic phase (CP) chronic myeloid leukemia (CML). The current analysis evaluated potential bosutinib pharmacokinetic-pharmacodynamic relationships.

METHODS

Bosutinib exposure metrics at steady state were estimated from a previously developed population pharmacokinetic model. Safety and efficacy metrics were from two clinical studies of bosutinib 500 mg/day in patients with CP CML.

RESULTS

The analysis included 749 patients (aged 18-91 years; mean weight, 75 kg; 54% male). An exposure-response relationship was identified for the pooled incidence (but not severity) of diarrhea, with predicted probability ranging from 0.575 to 0.797 for the lowest and highest area under the curve bins, respectively; a weak relationship was also observed for the incidence of rash (predicted probability, 0.216-0.419). There was no evidence of an exposure-response relationship for nausea, vomiting, neutropenia, thrombocytopenia, or elevated alanine and aspartate aminotransferases. Exposure-response relationships were observed in patients with newly diagnosed CP CML for complete cytogenetic response at 1 year (predicted probability, 0.476-0.650), major molecular response at 1 year (0.238-0.497), and cumulative complete hematologic response (CHR) at 1 year (0.605-0.763). Patients with previously treated CP CML showed no exposure-response relationship for major cytogenetic response at 24 weeks (0.320); for CHR, higher bosutinib exposure was associated with a lower probability of response (0.926-0.743).

CONCLUSIONS

The absence of exposure-response relationships for some safety and efficacy metrics may reflect bosutinib exposure metrics that exceeded the half-maximal inhibitory values and achieved a maximum effect.

Dasatinib for the treatment of Philadelphia chromosome-positive leukemias

INTRODUCTION

Dasatinib is a dual Abl/Src tyrosine kinase inhibitor (TKI), which was developed to treat patients with chronic myelogenous leukemia (CML), who had failed or were intolerant to therapy with imatinib.

AREAS COVERED

In this article, we review preclinical and clinical studies with dasatinib for the therapy of Philadelphia (Ph)-positive leukemias.

EXPERT OPINION

Dasatinib is very effective in the setting of CML resistance or intolerance to imatinib, particularly in patients in chronic phase (CP). Dasatinib is also effective against most BCR-ABL1 mutations that arise during therapy with imatinib. Further studies have confirmed activity of dasatinib as a single-agent, and combined with chemotherapy, for the treatment of patients with Philadelphia-positive acute lymphoblastic leukemia (Ph+-ALL). More recently, randomized trials have demonstrated that dasatinib is superior to imatinib in the initial therapy of patients with CML, and the drug was approved by the FDA for this indication in 2011.

Bosutinib versus imatinib in newly diagnosed chronic-phase chronic myeloid leukemia: results from the BELA trial

PURPOSE

Bosutinib is an oral Src/Abl tyrosine kinase inhibitor. The phase III Bosutinib Efficacy and Safety in Newly Diagnosed Chronic Myeloid Leukemia (BELA) trial compared bosutinib with imatinib in newly diagnosed, chronic-phase chronic myeloid leukemia (CML).

PATIENTS AND METHODS

A total of 502 patients were randomly assigned 1:1 to bosutinib 500 mg per day or imatinib 400 mg per day.

RESULTS

The complete cytogenetic response (CCyR) rate at 12 months was not different for bosutinib (70%; 95% CI, 64% to 76%) versus imatinib (68%; 95% CI, 62% to 74%; two-sided P = .601); therefore, the study did not achieve its primary end point. The major molecular response (MMR) rate at 12 months was higher with bosutinib (41%; 95% CI, 35% to 47%) compared with imatinib (27%; 95% CI, 22% to 33%; two-sided P < .001). Time to CCyR and MMR was faster with bosutinib compared with imatinib (two-sided P < .001 for both). On-treatment transformation to accelerated/blast phase occurred in four patients (2%) on bosutinib compared with 10 patients (4%) on imatinib. A total of three CML-related deaths occurred on the bosutinib arm compared with eight on the imatinib arm. The safety profiles of bosutinib and imatinib were distinct; GI and liver-related events were more frequent with bosutinib, whereas neutropenia, musculoskeletal disorders, and edema were more frequent with imatinib.

CONCLUSION

This ongoing trial did not meet its primary end point of CCyR at 12 months, despite the observed higher MMR rate at 12 months, faster times to CCyR and MMR, fewer on-treatment transformations to accelerated/blast phase, and fewer CML-related deaths with bosutinib compared with imatinib. Each drug had a distinct safety profile.

A randomized trial of dasatinib 100 mg versus imatinib 400 mg in newly diagnosed chronic-phase chronic myeloid leukemia

Tyrosine kinase inhibitor therapy with imatinib (IM), dasatinib (DAS), or nilotinib is very effective in chronic-phase chronic myeloid leukemia. Two hundred fifty-three patients with newly diagnosed chronic-phase chronic myeloid leukemia were randomized to IM 400 mg/day or DAS 100 mg/day. The proportion of patients achieving a complete cytogenetic remission rate was superior with DAS (84% vs 69%), as was the 12-month molecular response by the proportions of patients achieving > 3-log, > 4-log, and > 4.5-log reduction in BCR-ABL transcript levels. Overall and progression-free survival was similar in the 2 arms. Among patients who achieved hematologic CR, 3-year relapse-free survival was 91% with DAS and 88% with IM 400 mg. Grade 3 and 4 toxicities were most commonly hematologic, including thrombocytopenia in 18% and 8% of DAS and IM patients, respectively. DAS induced more complete cytogenetic response and deeper molecular responses after 12 months, compared with IM 400 mg, and with a median follow-up of 3.0 years there have been very few deaths, relapses, or progressions in the 2 arms. In summary, DAS compared with IM appeared to have more short-term cytogenetic and molecular response, more hematologic toxicity, and similar overall survival. This trial is registered at www.clinicaltrials.gov as NCT00070499.

Dasatinib in chronic myeloid leukemia: a limited Indian experience

AIM

To report our experience of the use of dasatinib in various phases of chronic myeloid leukemia (CML).

METHODS

Ten patients in various phases of CML, not responding to imatinib and started on dasatinib, were included and analyzed. The baseline characteristics of the patients and their salient features including the duration and response to initial therapy as well as to dasatinib, were noted.

RESULTS

Before starting dasatinib three patients were in chronic phase of CML while seven others were in the progressive phase (accelerated and blast phase) of CML. Half the patients developed transient grade 3 and 4 toxicities to dasatinib. Overall, the tolerability of the drug in all 10 patients was acceptable and none discontinued treatment. Three patients died due to progressive disease while the remaining seven are continuing the drug with the disease still under cytogenetic or hematological remission. Of the 10 patients, seven achieved complete hematological response and two of the accelerated phase/blast crisis patients achieved complete cytogenetic response. Overall, dasatinib was able to control disease for a median of 20.6 months.

CONCLUSION

Despite small sample size and insufficient information on mutational analysis, dasatinib is effective in CML in India. Cost limits the use of second-generation tyrosine kinase inhibitors in India. Our observation is not suitable for survival analysis but the difference made by dasatinib in progressive disease and its tolerability needs to be acknowledged.

Association between imatinib transporters and metabolizing enzymes genotype and response in newly diagnosed chronic myeloid leukemia patients receiving imatinib therapy

Imatinib has so far been the first-choice treatment in chronic myeloid leukemia with excellent results. However, only a proportion of patients achieve major molecular response - hence the need to find biological predictors of outcome to select the optimal therapeutic strategy now that more potent inhibitors are available. We investigated a panel of 20 polymorphisms in seven genes, potentially associated with the pharmacogenetics of imatinib, in a subset of 189 patients with newly diagnosed chronic myeloid leukemia enrolled in the TOPS trial. The analysis included polymorphisms in the transporters hOCT1, MDR1, ABCG2, OCTN1, and OATP1A2, and in the metabolizing genes CYP3A4 and CYP3A5. In the overall population, the OCTN1 C allele (rs1050152), a simple combination of polymorphisms in the hOCT1 gene and another combination in the genes involved in imatinib uptake were significantly associated with major molecular response. The combination of polymorphisms in imatinib uptake was also significantly associated with complete molecular response. Analyses restricted to Caucasians highlighted the significant association of MDR1 CC (rs60023214) genotype with complete molecular response. We demonstrate the usefulness of a pharmacogenetic approach for stratifying patients with chronic myeloid leukemia according to their likelihood of achieving a major or complete molecular response to imatinib. This represents an attractive opportunity for therapy optimization, worth testing in clinical trials.

Treatments for chronic myeloid leukemia: a qualitative systematic review

Background

Chronic myeloid leukemia (CML) is a myeloproliferative disorder of blood stem cells. The tyrosine kinase inhibitor (TKI) imatinib was the first targeted therapy licensed for patients with chronic-phase CML, and its introduction was associated with substantial improvements in response and survival compared with previous therapies. Clinical trial data are now available for the second-generation TKIs (nilotinib, dasatinib, and bosutinib) in the first-, second-, and third-line settings. A qualitative systematic review was conducted to qualitatively compare the clinical effectiveness, safety, and effect on quality of life of TKIs for the management of chronic-, accelerated-, or blast-phase CML patients.

Methods

Included studies were identified through a search of electronic databases in September 2011, relevant conference proceedings and the grey literature.

Results

In the first-line setting, the long-term efficacy (up to 8 years) of imatinib has been confirmed in a single randomized controlled trial (International Randomized Study of Interferon [IRIS]). All second-generation TKIs reported lower rates of transformation, and comparable or superior complete cytogenetic response (CCyR), major molecular response (MMR), and complete molecular response rates compared with imatinib by 2-year follow-up. Each of the second-generation TKIs was associated with a distinct adverse-event profile. Bosutinib was the only second-generation TKI to report quality-of-life data (no significant difference compared with imatinib treatment). Data in the second- and third-line setting confirmed the efficacy of the second-generation TKIs in either imatinib-resistant or -intolerant patients, as measured by CCyR and MMR rates.

Conclusion

Data from first-line randomized controlled trials reporting up to 2-year follow-up indicate superior response rates of the second-generation TKIs compared with imatinib. Current evidence from single-arm studies in the second-line setting confirm that nilotinib, dasatinib, and bosutinib are valuable treatment options for the significant subgroup of patients who are intolerant or resistant to imatinib treatment.

Jakinibs: a new class of kinase inhibitors in cancer and autoimmune disease

Cytokines are critical for normal cell growth and immunoregulation but also contribute to growth of malignant cells and drive immune-mediated disease. A large subset of immunoregulatory cytokines uses the type I and type II cytokine receptors and pharmacological targeting of these cytokines/cytokines receptors has proven to be efficacious in treating immune and inflammatory diseases. These receptors rely on Janus family of kinases (Jaks) for signal transduction. Recently the first Jak inhibitor (jakinib) has been approved by the FDA and a second has been recommended for approval. Many other Jakinibs are likely to follow and in this brief review, we will discuss the state-of-the art of this new class of pharmacological agents.

Initial treatment for patients with chronic myeloid leukemia

The first-line treatment of chronic myeloid leukemia is based on the three currently available tyrosine kinase inhibitors (TKIs), namely imatinib, nilotinib and dasatinib. Nilotinib and dasatinib are more potent, and it is predicted that, in comparison with imatinib, they can reduce the risk of progression and increase the number of the patients who can discontinue the treatment without relapsing. Other TKIs are still being developed and may help to improve treatment options further on. Hydroxyurea has no longer a role. Allogeneic stem cell transplantation is the treatment of choice for the advanced phases, and in case of resistance to at least two TKIs.

Advances in treatment of chronic myeloid leukemia with tyrosine kinase inhibitors: the evolving role of Bcr–Abl mutations and mutational analysis

Over the last decade, the treatment of chronic myeloid leukemia has progressed tremendously. The first-generation tyrosine kinase inhibitor imatinib is now flanked by two second-generation molecules, dasatinib and nilotinib – and others are in advanced clinical development. One of the reasons for such intensive research on novel compounds is the problem of resistance, that is thought to be caused, in a proportion of cases, by point mutations in Bcr–Abl. In this article, the authors review how the biological and clinical relevance of Bcr–Abl mutations has evolved in parallel with the availability of more and more therapeutic options. The authors also discuss the practical relevance of Bcr–Abl mutation analysis and how this tool should best be integrated in the optimal clinical management of chronic myeloid leukemia patients.

Incidence, risk factors and management of pleural effusions during dasatinib treatment in unselected elderly patients with chronic myelogenous leukaemia

To assess the most important features and clinical impact of pleural effusions, which are a common toxicity during dasatinib treatment and often impair its high efficacy, 172 unselected consecutive patients with chronic myelogenous leukaemia in chronic phase treated in 27 Italian centres, with dasatinib when aged >60 years for resistance/intolerance to imatinib, were examined. During treatment, 52/172 patients (30.2%) presented pleural effusion, which was grades 1-2 in 38 patients and grades 3-4 in 14 patients (8.1% of the entire cohort of patients), according to the WHO scale; in 14/52 patients (26.9%), there was a concomitant pericardial effusion. Pleural effusion was recurrent in 25/52 patients (48.0%). Median time from dasatinib to first pleural effusion was 11.0 months (interquartile range 3.6-18.6). Eleven patients (6.4%) required permanent dasatinib discontinuation. Only presence of concomitant pulmonary disease ( p = 0.035) and initial daily dose of dasatinib (140 mg vs 100 mg, p = 0.014) were significantly associated with pleural effusions. There were no differences among patients with or without pleural effusions as concerns response rates and overall survival. Pleural effusions were common in our unselected 'real-life' population of elderly patients but were clinically manageable and did not seem to affect treatment results.

Managing inadequate responses to frontline treatment of chronic myeloid leukemia: a case-based review

The tyrosine kinase inhibitors (TKIs) imatinib, nilotinib, and dasatinib are the standard of care for treating patients with newly diagnosed chronic-phase chronic myeloid leukemia (CML). Compared with interferon-based treatment, the previous standard of care, imatinib is associated with significantly higher cytogenetic response rates and prolonged overall survival. Nilotinib and dasatinib, both newer and more potent TKIs, significantly improve cytogenetic and molecular response rates compared with imatinib. Despite significant advances in CML treatment enabled by the TKIs, a fraction of patients who receive frontline treatment with a TKI demonstrate inadequate response. The reasons for this vary, but in many cases, inadequate response can be attributed to non-adherence to the treatment regimen, intolerance to the drug, intrinsic or acquired resistance to the drug, or a combination of reasons. More often than not, strategies to improve response necessitate a change in treatment plan, either a dose adjustment or a switch to an alternate drug, particularly in the case of drug intolerance or drug resistance. Improved physician-patient communication and patient education are effective strategies to address issues relating to adherence and intolerance. Because inadequate response to TKI treatment correlates with poor long-term outcomes, it is imperative that patients who experience intolerance or who fail to achieve appropriate responses are carefully evaluated so that appropriate treatment modifications can be made to maximize the likelihood of positive long-term outcome.

AMPK in BCR-ABL expressing leukemias. Regulatory effects and therapeutic implications

The abnormal BCR-ABL oncoprotein is a constitutively active tyrosine kinase driving aberrant proliferation of transformed hematopoietic cells. BCR-ABL regulates activation of many mitogenic and pro-survival pathways, including the PI 3'K/AKT/mTOR pathway that controls various effectors and regulates initiation of mRNA translation in mammalian cells. Although tyrosine kinase inhibitors (TKIs) that target the ABL kinase domain have remarkable clinical activity and have dramatically changed the natural history of Ph+ leukemias, resistance to these agents also develops via a wide range of mechanisms. Efforts to target the PI3'K/AKT/mTOR signaling pathway using kinase inhibitors have been the focus of extensive ongoing investigations by several research groups. Here we review the effects of activation of the AMPK kinase, which regulates downstream targeting and inhibition of mTOR. The potential for future clinical-translational applications of AMPK activators such as AICAR, metformin and resveratrol for the treatment of chronic myelogenous leukemia (CML) and Ph+ acute lymphoblastic leukemia (ALL) are discussed.

Development of an effective therapy for chronic myelogenous leukemia

Targeted small-molecule drugs have revolutionized treatment of chronic myeloid leukemia (CML) during the last decade. These agents interrupt a constitutively active BCR-ABL, the causative agent for CML, by interfering with adenosine 5' triphosphate-dependent ABL tyrosine kinase. Although the efficacy of tyrosine kinase inhibitors (TKIs) has resulted in overall survival of greater than 90%, TKIs are not curative. Moreover, no currently approved TKIs are effective against the T315I BCR-ABL variant. However, a new generation of TKIs with activity against T315I is on the horizon. We will highlight the clinical utility of historical CML therapeutics, those used today (first- and second-generation TKIs), and discuss treatment modalities that are under development. Recent advances have illuminated the complexity of CML, especially within the marrow microenvironment. We contend that the key to curing CML will involve strategies beyond targeting BCR-ABL because primitive human CML stem cells are not dependent on BCR-ABL. Ultimately, drug combinations or exploiting synthetic lethality may transform responses into definitive cures for CML.

Analysis of mutations in the BCR-ABL1 kinase domain, using direct sequencing: detection of the T315I mutation in bone marrow CD34+ cells of a patient with chronic myelogenous leukemia 6 months prior to its emergence in peripheral blood

BACKGROUND AND OBJECTIVE

It has been shown that the occurrence of the BCR-ABL1 T315I mutation leads to a very poor therapeutic outcome in chronic myelogenous leukemia (CML) patients treated with tyrosine kinase inhibitors. Therefore, early detection of this mutation could potentially lead to early therapeutic intervention and a better prognosis with the ongoing treatment regimen.

METHODS

The detection of BCR-ABL1 kinase domain (KD) mutations was performed by direct sequencing of peripheral blood (PB), total bone marrow (BM), and BM CD34+ cells from a reported CML patient.

RESULTS

In this patient, the T315I mutation was detected in BM CD34+ cells 6 months prior to its emergence in PB, suggesting evolution and expansion of the T315I mutation clone, which most likely originated from more primitive CML cells.

CONCLUSION

Our finding reflects the natural development of a T315I mutation within the hematopoietic system of the reported patient and indicates the importance of BCR-ABL1 mutation monitoring in more primitive cell populations. Considering the natural history of T315I development in this reported CML case, we hypothesize that BCR-ABL1 KD mutations may be pre-concentrated in more primitive CML cells, which subsequently expand into the PB. These findings may have future implications for the strategy used for detecting BCR-ABL1 mutations.

Oxidative stress is involved in Dasatinib-induced apoptosis in rat primary hepatocytes

Dasatinib, a multitargeted inhibitor of BCR-ABL and SRC kinases, exhibits antitumor activity and extends the survival of patients with chronic myeloid leukemia (CML) and Philadelphia chromosome-positive acute lymphoblastic leukemia (ALL). However, some patients suffer from hepatotoxicity, which occurs through an unknown mechanism. In the present study, we found that Dasatinib could induce hepatotoxicity both in vitro and in vivo. Dasatinib reduced the cell viability of rat primary hepatocytes, induced the release of alanine aminotransferase (ALT) and lactate dehydrogenase (LDH) in vitro, and triggered the ballooning degeneration of hepatocytes in Sprague-Dawley rats in vivo. Apoptotic markers (chromatin condensation, cleaved caspase-3 and cleaved PARP) were detected to indicate that the injury induced by Dasatinib in hepatocytes in vitro was mediated by apoptosis. This result was further validated in vivo using terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assays. Here we found that Dasatinib dramatically increased the level of reactive oxygen species (ROS) in hepatocytes, reduced the intracellular glutathione (GSH) content, attenuated the activity of superoxide dismutase (SOD), generated malondialdehyde (MDA), a product of lipid peroxidation, decreased the mitochondrial membrane potential, and activated nuclear factor erythroid 2-related factor 2 (Nrf2) and mitogen-activated protein kinases (MAPK) related to oxidative stress and survival. These results confirm that oxidative stress plays a pivotal role in Dasatinib-mediated hepatotoxicity. N-acetylcysteine (NAC), a typical antioxidant, can scavenge free radicals, attenuate oxidative stress, and protect hepatocytes against Dasatinib-induced injury. Thus, relieving oxidative stress is a viable strategy for reducing Dasatinib-induced hepatotoxicity.

Molecular resistance: an early indicator for treatment change?

Vigilant monitoring of a patient's response to current treatment is imperative to the management of chronic myeloid leukemia (CML). Early identification of treatment failure may increase the probability that alternative therapy will be effective. This review discusses the use of molecular monitoring in the timely detection of failure of imatinib treatment. Changes in the levels of BCR-ABL transcripts are predictive of response or relapse. Patients achieving a major molecular response (MMR) within 12 months of treatment may experience longer cytogenetic remission. Accumulating evidence also suggests that lower transcript levels observed ≤ 6 months after the start of treatment are associated with improved patient outcomes. For patients with primary or secondary imatinib resistance (or intolerance), dasatinib or nilotinib may be prescribed. These agents have demonstrated activity in patients harboring imatinib-resistant BCR-ABL mutations, except for the T315I substitution.

Identification of side effects associated with intolerance to BCR-ABL inhibitors in patients with chronic myeloid leukemia

Clinical intolerance occurs when the toxicity of a medication outweighs its clinical benefit. Early recognition of clinical intolerance to BCR-ABL inhibitors used for chronic myeloid leukemia (CML) is important for maximizing patient benefit. In CML, most side effects associated with BCR-ABL inhibitor therapy are mild and easily managed, so recognizing, monitoring, and addressing serious side effects may ensure optimal outcome. However, a subset of patients will be intolerant to first-line imatinib. Patients who experience unresponsive grade 3 or any grade 4 nonhematologic side effects to imatinib may require discontinuation and switching to second-line therapies, such as dasatinib or nilotinib, after identification of intolerance. The most common side effects associated with dasatinib and nilotinib are hematologic and generally are reversible with dose adjustment. Pleural effusions are more common with dasatinib use and may be managed by dose interruption and reduction. Both drugs possess warnings regarding QT prolongation, but nilotinib carries a black box warning for QT prolongation and sudden death.

Epigenetic therapy with hydralazine and magnesium valproate reverses imatinib resistance in patients with chronic myeloid leukemia

The epigenetic drugs hydralazine and valproate were administered in a compassionate manner to 8 patients with chronic myeloid leukemia (CML) refractory to imatinib. Two patients had a complete hematologic response (25%),1 major cytogenetic response, 1 complete cytogenetic response (25% any cytogenetic response), and 3 (37.5%)stable disease. No grade 3 or 4 toxicity was observed. These results show the ability of epigenetic therapy to revert imatinib resistance.

BACKGROUND

Epigenetic alterations participate in the development of acquired resistance to imatinib, hence, the DNA methylation, and histone deacetylase inhibitors hydralazine and valproate, respectively, has the potential to overcome it.

PATIENT AND METHODS

A series of 8 patients with chronic myeloid leukemia (CML) refractory to imatinib mesylate with no access to second-generation tyrosine kinase inhibitors were treated with hydralazine and valproate in a compassionate manner. Clinical efficacy and safety of these drugs added to imatinib mesylate were evaluated.

RESULTS

Two patients were in the blast phase, 5 were in the accelerated phase, and 1 was in the chronic phase. All the patients continued with the same dose of imatinib that they had been receiving at the time of development of resistance, with a median dose of 600 mg daily (range, 400-800 mg). The median time from diagnosis of CML to the start of hydralazine and valproate was 53.6 months (range, 19-84 months). Two (25%) patients had a complete hematologic response, one (12.5%) had an major cytogenetic response, and one (12.5%) had a complete cytogenetic response. Three (37.5%) patients had stable disease, and only one (12.5%) patient failed to respond. At a median follow-up time of 18 months (range, 3-18 months), the median survival had not been reached, and the projected overall survival was 63%. All the patients had mild neurologic toxicity, including distal tremor and somnolence. No grade 3 or 4 toxicity was observed.

CONCLUSIONS

Our results suggest that the epigenetic drugs hydralazine and valproate revert the resistance to imatinib in patients with CML.

Rapid quantitative detection of the T315I mutation in patients with chronic myelogenous leukemia

Acquired resistance to tyrosine kinase inhibitors (TKIs) in the treatment of chronic myelogenous leukemia (CML) is frequently caused by point mutations in the ABL kinase domain of the BCR-ABL fusion gene. The T315I mutation is the most common mutation found in the kinase domain and leads to complete resistance to existing TKIs. Sensitive and specific approaches for detecting this mutation in patient specimens can provide valuable information to guide treatment decisions and monitor their effectiveness. Here, we describe an allele-specific real-time polymerase chain reaction method to distinguish and quantify wild type or T315I mutant ABL transcripts. This approach has high specificity in identifying mutant transcripts and shows minimal interference from wild-type transcripts. As few as 5 copies of the T315I mutant transcript or 0.025% (2.5×10(-4)) T315I mutant transcripts could be detected by this method. This approach requires no additional specialized reagents other than those used in standard real-time polymerase chain reaction and therefore may be easily incorporated as an effective strategy for the early detection and monitoring of TKI resistance in patients with CML.

Adherence to treatment with second-line therapies, dasatinib and nilotinib, in patients with chronic myeloid leukemia

BACKGROUND AND OBJECTIVE

Previous studies have shown that long-term outcomes are more favorable for patients newly diagnosed with chronic myeloid leukemia (CML) if a complete cytogenetic response is achieved within ≤12 months of diagnosis. Because continuous and adequate dosing is important to achieve this outcome, it is important to understand treatment adherence as part of managing long-term CML therapy. While studies regarding imatinib suggest that adherence varies widely, data addressing adherence to newer breakpoint cluster region-Abelson (BCR-ABL) inhibitors (dasatinib and nilotinib) are sparse. This study evaluates real-world adherence in patients diagnosed with CML receiving dasatinib or nilotinib as second-line therapy.

RESEARCH DESIGN AND METHODS

Using the HealthCore Integrated Research Database (HIRD(SM)), patients with ≥1 International Classification of Diseases, 9th edition/revision, Clinical Modification (ICD-9-CM) code for CML (205.1x ) and ≥1 prescription for imatinib from January 1, 2001 to June 30, 2010 were identified. Analysis was limited to patients who switched to second-line dasatinib or nilotinib. Dasatinib exposure was stratified by dose (≤100 mg/day or ≥140 mg/day) to account for dasatinib label changes.

MAIN OUTCOME MEASURES

Medication possession ratio (MPR) was used to calculate adherence and Cox proportional hazard models were used to quantify poor rates of adherence (i.e., MPR <85%).

RESULTS

Of 2064 imatinib-exposed patients, 197 received dasatinib (≤100 mg/day, n = 112; ≥140 mg/day, n = 85) and 53 received nilotinib (400 mg BID, n = 46; 400 mg QD, n = 7) as second-line therapy. Mean exposure durations were 276 days for dasatinib (≤100 mg, 275 days; ≥140 mg, 276 days) and 170 days for nilotinib. Cox proportional hazard models quantifying rates of poor adherence (MPR < 85%) comparing nilotinib with dasatinib (adjusted for age, sex, duration of previous imatinib exposure, number of concomitant medications, presence of cardiovascular disease or diabetes) calculated hazard ratios of 1.6 (95% confidence interval [CI], 1.0-2.4) for nilotinib versus dasatinib overall, 1.9 (95% CI, 1.2-3.0) for nilotinib versus dasatinib ≤100 mg, and 1.2 (95% CI, 0.7-2.0) for nilotinib versus dasatinib ≥140 mg.

CONCLUSIONS

While this study is limited by use of claims data to identify CML and adherence, claims based data have been widely used to evaluate the association between treatment use and clinical outcomes. When stratified by dose, patients receiving second-line nilotinib were almost two times more likely to have poor adherence compared with patients receiving second-line dasatinib at the current approved dose of 100 mg once daily.

Targeted therapy for patients with chronic myeloid leukemia: clinical trial experience and challenges in inter-trial comparisons

The treatment of chronic myeloid leukemia (CML) was revolutionized by the introduction of the targeted tyrosine kinase inhibitor (TKI) imatinib mesylate. Later, to improve efficacy and tolerability, the more potent TKIs dasatinib and nilotinib were evaluated in CML. Clinicians comparing the clinical efficacy of TKIs face considerable challenges, including the variable treatment histories of patients receiving second-line therapy. The aim of this review is to highlight the pitfalls and possible solutions for comparing efficacy across disparate CML trials. Comparison of efficacy across trials is aided by careful consideration of possible confounding factors, including treatment history, definitions of imatinib intolerance or resistance, and BCR-ABL mutational status at baseline. However, methods exist to improve the comparability of data from different trials, yielding a more clinically and statistically meaningful inter-trial comparison.

Adverse cutaneous reactions secondary to tyrosine kinase inhibitors including imatinib mesylate, nilotinib, and dasatinib

Imatinib mesylate is the first of a novel group of drugs that specifically target protein tyrosine kinases, which are central to the pathogenesis of human cancer. It has been approved for the treatment of chronic myeloid leukemia and gastrointestinal stromal tumor and has been found efficacious in other neoplastic diseases. Nilotinib and dasatinib, a second-generation of tyrosine kinase inhibitors (TKIs), were developed in response to findings of emerging imatinib resistance or intolerance to the drug. Cutaneous reactions are the most common nonhematologic side effect of these drugs, and their management is challenging especially in the absence of alternative anticancer agents. The present review focuses on the clinical characteristics and the hypothesized molecular pathogenesis of these first- and second-generation TKIs' cutaneous side effects, and approaches to their treatment. The wide range of adverse effects clarifies the difficulty in designing a truly antitumoral TKI.

Additional chromosome abnormalities, BCR-ABL tyrosine kinase domain mutations and clinical outcome in Hungarian tyrosine kinase inhibitor-resistant chronic myelogenous leukemia patients

BACKGROUND

Additional chromosome abnormalities (ACAs), mutations of the BCR-ABL tyrosine kinase domain (TKD) and BCR-ABL splice variants may cause resistance to first- and second-generation tyrosine kinase inhibitors (TKIs) in chronic myelogenous leukemia (CML) and Philadelphia-positive (Ph+) acute lymphoid leukemia (ALL).

METHODS

Karyotyping and BCR-ABL TKD mutation screening were performed in 71 imatinib-resistant CML patients and 6 Ph+ ALL patients. A total of 56 out of these 77 patients received second-generation TKI.

RESULTS

ACAs were present in 30 of 65 imatinib-resistant patients (46%). In 27 of 74 imatinib-resistant patients (36%), 15 different BCR-ABL TKD mutations were detected. Mutations were found in 25% of chronic-phase patients (12/47), 33% of accelerated-phase patients (5/15), 71% of blast crisis CML patients (5/7) and 100% of ALL patients. In nilotinib-resistant patients, Y253H, T315I and F359I/V mutations were detected; in dasatinib-resistant patients, L248M, E279K and T315I mutations were detected. T315I was found more frequently in patients on dasatinib than on imatinib therapy. The presence of ACAs predicted shorter survival during first- and second-generation TKI therapy, while TKD mutations only influenced survival during second-generation TKI therapy.

CONCLUSION

For patients with TKI resistance, mutation and ACA screening may play a role in identifying patients with poorer prognosis.

Responses to second-line tyrosine kinase inhibitors are durable: an intention-to-treat analysis in chronic myeloid leukemia patients

Second-generation tyrosine kinase inhibitors (2G-TKIs) are effective at inducing complete cytogenetic responses (CCyRs) in approximately half of chronic myeloid leukemia patients treated while still in the chronic phase and after failing imatinib. It is less clear whether these responses are durable. In the present study, we report the clinical outcome of 119 patients who received a 2G-TKI as second-line treatment while still in the chronic phase. In an intention-to-treat analysis, the 4-year probabilities of overall and event-free survival were 81.9% and 35.3%, respectively. Sixty-two patients discontinued the initial 2G-TKI because of resistance or intolerance. To further explore the durability of cytogenetic responses, irrespective of the need for a third-line TKI, we used the concept of "current CCyR-survival" (c-CCyRS). The c-CCyRS at 4 years was 54.4%. After introduction of a 2G-TKI, 77 patients had a 3-month BCR-ABL1/ABL1 transcript ratio of ≤ 10% and had significantly superior overall survival (91.3% vs 72.1%, P = .02), event-free survival (49.3% vs 13.0%, P < .001), and c-CCyRS (67.2% vs 11.2%, P = .0001) compared with the 33 patients with ratios > 10%. The 3-month molecular response was the only independent predictor for overall survival. Using an intention-to-treat analysis, we have shown that the responses to second-line therapies are durable. Patients destined to fare poorly can be identified early during therapy.

Cost-effectiveness of dasatinib and nilotinib for imatinib-resistant or -intolerant chronic phase chronic myeloid leukemia

OBJECTIVES

To estimate the cost-effectiveness of dasatinib and nilotinib compared with high-dose imatinib for people with chronic phase chronic myeloid leukemia, which are resistant to normal-dose imatinib and compared with interferon-α for people intolerant to imatinib, from the perspective of the UK National Health Service.

METHODS

An an area under the curve partitioned survival model was developed to estimate the cost-effectiveness of dasatinib and nilotinib. Clinical effectiveness evidence was taken mostly from single-arm trials.

RESULTS

Both progression-free survival and overall survival are highly uncertain. In the base case, patients take nilotinib for much less time than dasatinib. Nilotinib is expected to dominate high-dose imatinib, yielding slightly more (0.32) quality-adjusted life years (QALYs) at slightly less cost (£11,100 [pound sterling]) per person. Dasatinib is predicted to provide slightly more (0.53) QALYs at substantially greater cost (£48,900), yielding a very high incremental cost-effectiveness ratio of £91,500 QALY against high-dose imatinib. Cost-effectiveness, however, changes radically under the plausible assumption that the drugs are taken for the same time. For people intolerant to imatinib, nilotinib is expected to yield an incremental cost-effectiveness ratio of £104,700/QALY, and dasatinib £82,600/QALY compared with interferon-α. Further, both drugs represent poor value for money for a range of plausible structural assumptions.

CONCLUSIONS

The model should be viewed as an exploratory analysis of the cost-effectiveness of dasatinib and nilotinib because it relies on many assumptions. Whilst clinical data remains immature, the cost-effectiveness of dasatinib and nilotinib for imatinib-resistant people is highly uncertain. Both nilotinib and dasatinib are highly unlikely to be cost-effective versus interferon-α for people intolerant to imatinib.

Hematologic toxicities of small molecule tyrosine kinase inhibitors

Small molecule tyrosine kinase inhibitors (TKIs) are potent anti-cancer targeted therapies. TKIs are considered safe and efficacious therapeutic modalities, and are generally tolerated well. However, they are associated with certain side effects including hematologic toxicities such as anemia, macrocytosis, neutropenia, thrombocytopenia, hemolytic anemia, bone marrow aplasia and necrosis. Thrombotic microangiopathy, arterial thromboembolism and splenic infarction can also occur following treatment with TKIs. Cytopenias are the most common adverse effects associated with these agents, and other hematologic toxicities are not frequent. It is essential for clinicians to monitor patients closely, and recognize those side effects as early as possible, in order to improve efficacy of small molecule TKIs and optimize outcomes. This article summarizes hematologic toxicities associated with the commonly used small molecule TKIs. It also provides practical strategies for the management of these toxicities.

Long circulating lectin conjugated paclitaxel loaded magnetic nanoparticles: a new theranostic avenue for leukemia therapy

Amongst all leukemias, Bcr-Abl positive chronic myelogenous leukemia (CML) confers resistance to native drug due to multi drug resistance and also resistance to p53 and fas ligand pathways. In the present study, we have investigated the efficacy of microtubule stabilizing paclitaxel loaded magnetic nanoparticles (pac-MNPs) to ascertain its cytotoxic effect on Bcr-Abl positive K562 cells. For active targeted therapy, pac-MNPs were functionalized with lectin glycoprotein which resulted in higher cellular uptake and lower IC₅₀ value suggesting the efficacy of targeted delivery of paclitaxel. Both pac-MNPs and lectin conjugated pac-MNPs have a prolonged circulation time in serum suggesting increased bioavailability and therapeutics index of paclitaxel in vivo. Further, the molecular mechanism pertaining to pac-induced cytotoxicity was analyzed by studying the involvement of different apoptotic pathway proteins by immunoblotting and quantitative PCR. Our study revealed simultaneous activation of JNK pathway leading to Bcr-Abl instability and the extrinsic apoptotic pathway after pac-MNPs treatment in two Bcr-Abl positive cell lines. In addition, the MRI data suggested the potential application of MNPs as imaging agent. Thus our in vitro and in vivo results strongly suggested the pac-MNPs as a future prospective theranostic tool for leukemia therapy.

Suboptimal responses in chronic myeloid leukemia: implications and management strategies

The high response rates and increased survival associated with imatinib therapy prompted a paradigm shift in the management of chronic myeloid leukemia. However, 25% to 30% of imatinib-treated patients develop drug resistance or intolerance, increasing the risk of disease progression and poor prognosis. In 2006, the European LeukemiaNet proposed criteria to identify patients with a suboptimal response to, or failure associated with, imatinib; these recommendations were updated in 2009. Suboptimal responders represent a unique treatment challenge. Although they may respond to continued imatinib therapy, their long-term outcomes may not be as favorable as those for optimally responding patients. Validation studies demonstrated that suboptimal responders are a heterogeneous group, and that the prognostic implications of suboptimal response vary by time point. There are few data derived from clinical trials to guide therapeutic decisions for these patients. Clinical trials are currently underway to assess the efficacy of newer tyrosine kinase inhibitors in this setting. Identification of suboptimal responders or patients failing treatment using hematologic, cytogenetic, and molecular techniques allows physicians to alter therapy earlier in the treatment course to improve long-term outcomes.

Safety and efficacy of bosutinib (SKI-606) in chronic phase Philadelphia chromosome-positive chronic myeloid leukemia patients with resistance or intolerance to imatinib

Bosutinib, a dual Src/Abl kinase inhibitor, has shown potent activity against chronic myeloid leukemia (CML). In this phase 1/2 study we evaluated bosutinib in patients with chronic phase imatinib-resistant or imatinib-intolerant CML. Part 1 was a dose-escalation study to determine the recommended starting dose for part 2; part 2 evaluated the efficacy and safety of bosutinib 500 mg once-daily dosing. The study enrolled 288 patients with imatinib-resistant (n = 200) or imatinib-intolerant (n = 88) CML and no other previous kinase inhibitor exposure. At 24 weeks, 31% of patients achieved major cytogenetic response (primary end point). After a median follow-up of 24.2 months, 86% of patients achieved complete hematologic remission, 53% had a major cytogenetic response (41% had a complete cytogenetic response), and 64% of those achieving complete cytogenetic response had a major molecular response. At 2 years, progression-free survival was 79%; overall survival at 2 years was 92%. Responses were seen across Bcr-Abl mutants, except T315I. Bosutinib exhibited an acceptable safety profile; the most common treatment-emergent adverse event was mild/moderate, typically self-limiting diarrhea. Grade 3/4 nonhematologic adverse events (> 2% of patients) included diarrhea (9%), rash (9%), and vomiting (3%). These data suggest bosutinib is effective and tolerable in patients with chronic phase imatinib-resistant or imatinib-intolerant CML. This trial was registered at http://www.clinicaltrials.gov as NCT00261846.

[A therapeutic improvement: second generation tyrosine kinase inhibitors (TKI 2) in the treatment of chronic myelogenous leukemia]

Second-generation tyrosine kinase inhibitors (TKI 2) represent a recent important improvement in the treatment of Philadelphia positive leukemias. These agents are a suitable major option if resistance or significant imatinib intolerance occurs in chronic and accelerated phase CML. They are now introduced as first line therapy in chronic phase CML where they induce cytogenetic and molecular response rates never seen to date, which is promising for long-term survival. We propose here an analysis of the main current data available for the use of TKI 2 in CML.

Sensitive detection of BCR-ABL1 mutations in patients with chronic myeloid leukemia after imatinib resistance is predictive of outcome during subsequent therapy

PURPOSE

BCR-ABL1 mutation analysis is recommended to facilitate selection of appropriate therapy for patients with chronic myeloid leukemia after treatment with imatinib has failed, since some frequently occurring mutations confer clinical resistance to nilotinib and/or dasatinib. However, mutations could be present below the detection limit of conventional direct sequencing. We developed a sensitive, multiplexed mass spectrometry assay (detection limit, 0.05% to 0.5%) to determine the impact of low-level mutations after imatinib treatment has failed.

PATIENTS AND METHODS

Mutation status was assessed in 220 patients treated with nilotinib or dasatinib after they experienced resistance to imatinib.

RESULTS

Mutations were detected by sequencing in 128 patients before commencing nilotinib or dasatinib therapy (switchover). In 64 patients, 132 additional low-level mutations were detected by mass spectrometry alone (50 of 132 mutations were resistant to nilotinib and/or dasatinib). When patients received the inhibitor for which the mutation confers resistance, 84% of the low-level resistant mutations rapidly became dominant clones detectable by sequencing, including 11 of 12 T315I mutations. Subsequent complete cytogenetic response rates were lower for patients with resistant mutations at switchover detected by sequencing (0%) or mass spectrometry alone (16%) compared with patients with other mutations or no mutations (41% and 49%, respectively; P < .001). Failure-free survival among the 100 patients with chronic phase chronic myeloid leukemia when resistant mutations were detected at switchover by sequencing or mass spectrometry alone was 0% and 0% compared with 51% and 45% for patients with other mutations or no mutations (P = .003).

CONCLUSION

Detection of low-level mutations after imatinib resistance offers critical information to guide subsequent therapy selection. If an inappropriate kinase inhibitor is selected, there is a high risk of treatment failure with clonal expansion of the resistant mutant.

Resistance to cancer treatment: the role of somatic genetic events and the challenges for targeted therapies

Therapeutic resistance remains a major cause of cancer-related deaths. Resistance can occur from the outset of treatment or as an acquired phenomenon after an initial clinical response. Therapeutic resistance is an almost universal phenomenon in the treatment of metastatic cancers. The advent of molecularly targeted treatments brought greater efficacy in patients whose tumors express a particular target or molecular signature. However, resistance remains a predictable challenge. This article provides an overview of somatic genomic events that confer resistance to cancer therapies. Some examples, including BCR–Abl, EML4–ALK, and the androgen receptor, contain mutations in the target itself, which hamper binding and inhibitory functions of therapeutic agents. There are also examples of somatic genetic changes in other genes or pathways that result in resistance by circumventing the inhibitor, as in resistance to trastuzumab and BRAF inhibitors. Yet other examples results in activation of cytoprotective genes. The fact that all of these mechanisms of resistance are due to somatic changes in the tumor’s genome makes targeting them selectively a feasible goal. To identify and validate these changes, it is important to obtain biopsies of clinically resistant tumors. A rational consequence of this evolving knowledge is the growing appreciation that combinations of inhibitors will be needed to anticipate and overcome therapeutic resistance.

Activity and safety of dasatinib as second-line treatment or in newly diagnosed chronic phase chronic myeloid leukemia patients

Dasatinib is an oral dual tyrosine kinase inhibitor active against ABL1 and SRC family kinases. The US FDA approved it for the treatment of chronic myeloid leukemia (CML) patients in chronic, accelerated, or blastic phase with resistance or intolerance to imatinib therapy. Dasatinib is also indicated for the treatment of adults with Philadelphia chromosome-positive acute lymphoblastic leukemia who have become resistant to or intolerant of other treatments. The agent is now also approved for newly diagnosed chronic phase (CP) patients. This article reviews the pharmacokinetic and pharmacodynamic properties of dasatinib as well as clinical data limited to CP-CML patients. Four-year follow-up of a phase III dose-optimization trial confirmed that better progression-free survival (66%) and overall survival (82%) were obtained with a dose of 100 mg once daily (od) than with the standard 70 mg twice daily dosing (65% and 75%, respectively). The 100 mg od dosing schedule was also associated with the highest benefit-risk ratio for CP patients with resistant, intolerant, or suboptimal response. Recent results of a phase III trial in newly diagnosed patients demonstrated that dasatinib 100 mg od has superiority in terms of confirmed cytogenetic and molecular responses, with faster responses and high activity in high Sokal risk patients compared with standard-dose imatinib.