Optimizing therapy for patients with chronic myelogenous leukemia in chronic phase

Pharmacokinetics and pharmacodynamics of imatinib for optimal drug repurposing from cancer to COVID-19

INTRODUCTION

In the randomized double-blind placebo-controlled CounterCOVID study, oral imatinib treatment conferred a positive clinical outcome and a signal for reduced mortality in COVID-19 patients. High concentrations of alpha-1 acid glycoprotein (AAG) were observed in these patients and were associated with increased total imatinib concentrations.

AIMS

This post-hoc study aimed to compare the difference in exposure following oral imatinib administration in COVID-19 patients to cancer patients and assess assocations between pharmacokinetic (PK) parameters and pharmacodynamic (PD) outcomes of imatinib in COVID-19 patients. We hypothesize that a relatively higher drug exposure of imatinib in severe COVID-19 patients leads to improved pharmacodynamic outcome parameters.

METHODS

648 total concentration plasma samples obtained from 168 COVID-19 patients were compared to 475 samples of 105 cancer patients, using an AAG-binding model. Total trough concentration at steady state (Ct_trough) and total average area under the concentration-time curve (AUCt_ave) were associated with ratio between partial oxygen pressure and fraction of inspired oxygen (P/F), WHO ordinal scale (WHO-score) and liberation of oxygen supplementation (O₂lib). Linear regression, linear mixed effects models and time-to-event analysis were adjusted for possible confounders.

RESULTS

AUCt_ave and Ct_trough were respectively 2.21-fold (95%CI 2.07-2.37) and 1.53-fold (95%CI 1.44-1.63) lower for cancer compared to COVID-19 patients. Ct_trough, not AUCt_ave, associated significantly with P/F (β=-19,64; p-value=0.014) and O₂lib (HR 0.78; p-value= 0.032), after adjusting for sex, age, neutrophil-lymphocyte ratio, dexamethasone concomitant treatment, AAG and baseline P/F-and WHO-score. Ct_trough, but not AUCt_ave associated significantly with WHO-score. These results suggest an inverse relationship between PK-parameters, Ct_trough and AUCt_ave, and PD outcomes.

CONCLUSION

COVID-19 patients exhibit higher total imatinib exposure compared to cancer patients, attributed to differences in plasma protein concentrations. Higher imatinib exposure in COVID-19 patients did not associate with improved clinical outcomes. Ct_trough and AUCt_ave inversely associated with some PD-outcomes, which may be biased by disease course, variability in metabolic rate and protein binding. Therefore, additional PKPD analyses into unbound imatinib and its main metabolite may better explain exposure-response.

Elevated acute phase proteins affect pharmacokinetics in COVID-19 trials: Lessons from the CounterCOVID - imatinib study

This study aimed to determine whether published pharmacokinetic (PK) models can adequately predict the PK profile of imatinib in a new indication, such as coronavirus disease 2019 (COVID‐19). Total (bound + unbound) and unbound imatinib plasma concentrations obtained from 134 patients with COVID‐19 participating in the CounterCovid study and from an historical dataset of 20 patients with gastrointestinal stromal tumor (GIST) and 85 patients with chronic myeloid leukemia (CML) were compared. Total imatinib area under the concentration time curve (AUC), maximum concentration (C_max) and trough concentration (C_trough) were 2.32‐fold (95% confidence interval [CI] 1.34–3.29), 2.31‐fold (95% CI 1.33–3.29), and 2.32‐fold (95% CI 1.11–3.53) lower, respectively, for patients with CML/GIST compared with patients with COVID‐19, whereas unbound concentrations were comparable among groups. Inclusion of alpha1‐acid glycoprotein (AAG) concentrations measured in patients with COVID‐19 into a previously published model developed to predict free imatinib concentrations in patients with GIST using total imatinib and plasma AAG concentration measurements (AAG‐PK‐Model) gave an estimated mean (SD) prediction error (PE) of −20% (31%) for total and −7.0% (56%) for unbound concentrations. Further covariate modeling with this combined dataset showed that in addition to AAG; age, bodyweight, albumin, CRP, and intensive care unit admission were predictive of total imatinib oral clearance. In conclusion, high total and unaltered unbound concentrations of imatinib in COVID‐19 compared to CML/GIST were a result of variability in acute phase proteins. This is a textbook example of how failure to take into account differences in plasma protein binding and the unbound fraction when interpreting PK of highly protein bound drugs, such as imatinib, could lead to selection of a dose with suboptimal efficacy in patients with COVID‐19.

Prevalence of BCR-ABL T315I Mutation in Malaysian Patients with Imatinib-Resistant Chronic Myeloid Leukemia

Objective:

Chronic Myeloid Leukemia (CML) is caused by a reciprocal translocation between chromosomes 9 and 22, t(9;22) (q34;q11) which encodes for the BCR-ABL fusion protein. Discovery of Imatinib Mesylate (IM) as first line therapy has brought tremendous improvement in the management of CML. However, emergence of point mutations within the BCR-ABL gene particularly T315I mutation, affects a common BCR-ABL kinase contact residue which impairs drug binding thus contribute to treatment resistance. This study aims to investigate the BCR-ABL T315I mutation in Malaysian patients with CML.

Methods:

A total of 285 patients diagnosed with CML were included in this study. Mutation detection was performed using qualitative real-time PCR (qPCR).

Results:

Fifteen out of 285 samples (5.26%) were positive for T315I mutations after amplification with real-time PCR assay. From the total number of positive samples, six patients were in accelerated phase (AP), four in chronic phase (CP) and five in blast crisis (BC).

Conclusion:

Mutation testing is recommended for choosing various tyrosine kinase inhibitors (TKIs) to optimize outcomes for both cases of treatment failure or suboptimal response to imatinib. Therefore, detection of T315I mutation in CML patients are clinically useful in the selection of appropriate treatment strategies to prevent disease progression.

Challenges to Care and Medication Adherence of Patients With Chronic Myeloid Leukemia in a Resource Limited Setting: A Qualitative Study

The factors related to care of patients with chronic myeloid leukemia (CML) often affects treatment outcome. We examined adherence to medication and other challenges to care in our patients on treatment of CML. This qualitative study involved in-depth interviews of 20 patients with CML receiving free imatinib (Glivec) from the Glivec International Patients' Assistance Program. Data collected were thematically analyzed. Findings revealed that despite free drug assistance, there was relative lack of awareness resulting in inappropriate health-seeking behavior. The challenges cut across situations such as poverty, fear of the sustenance of the compassionate drug program, and living far away from the clinic. Forgetfulness was reported as the cause of poor adherence in this study. Suggested solutions include increasing community awareness, ensuring sustainability of the program and establishing more treatment centers nationwide. Strategies such as reminders and patents' support will improve drug adherence among this cohort.

Nilotinib impairs skeletal myogenesis by increasing myoblast proliferation

Background

Tyrosine kinase inhibitors (TKIs) are effective therapies with demonstrated antineoplastic activity. Nilotinib is a second-generation FDA-approved TKI designed to overcome Imatinib resistance and intolerance in patients with chronic myelogenous leukemia (CML). Interestingly, TKIs have also been shown to be an efficient treatment for several non-malignant disorders such fibrotic diseases, including those affecting skeletal muscles.

Methods

We investigated the role of Nilotinib on skeletal myogenesis using the well-established C2C12 myoblast cell line. We evaluated the impact of Nilotinib during the time course of skeletal myogenesis. We compared the effect of Nilotinib with the well-known p38 MAPK inhibitor SB203580. MEK1/2 UO126 and PI3K/AKT LY294002 inhibitors were used to identify the signaling pathways involved in Nilotinib-related effects on myoblast. Adult primary myoblasts were also used to corroborate the inhibition of myoblasts fusion and myotube-nuclei positioning by Nilotinib.

Results

We found that Nilotinib inhibited myogenic differentiation, reducing the number of myogenin-positive myoblasts and decreasing myogenin and MyoD expression. Furthermore, Nilotinib-mediated anti-myogenic effects impair myotube formation, myosin heavy chain expression, and compromise myotube-nuclei positioning. In addition, we found that p38 MAPK is a new off-target protein of Nilotinib, which causes inhibition of p38 phosphorylation in a similar manner as the well-characterized p38 inhibitor SB203580. Nilotinib induces the activation of ERK1/2 and AKT on myoblasts but not in myotubes. We also found that Nilotinib stimulates myoblast proliferation, a process dependent on ERK1/2 and AKT activation.

Conclusions

Our findings suggest that Nilotinib may have important negative effects on muscle homeostasis, inhibiting myogenic differentiation but stimulating myoblasts proliferation. Additionally, we found that Nilotinib stimulates the activation of ERK1/2 and AKT. On the other hand, we suggest that p38 MAPK is a new off-target of Nilotinib. Thus, there is a necessity for future studies to investigate the long-term effects of TKIs on skeletal muscle homeostasis, along with potential detrimental effects in cell differentiation and proliferation in patients receiving TKI therapies.

Electronic supplementary material

The online version of this article (10.1186/s13395-018-0150-5) contains supplementary material, which is available to authorized users.

BCR-ABL V280G Mutation, Potential Role in Imatinib Resistance: First Case Report

INTRODUCTION

The identification of BCR-ABL expression as the defining leukemogenic event in chronic myeloid leukemia (CML) and the introduction of BCR-ABL tyrosine kinase inhibitors in 2001 have revolutionized disease management, leading to a reduction in mortality rates and accordingly an increase in the estimated prevalence of CML.

CASE REPORT

Based on medical records and clinical follow-up, the authors present the case of a Philadelphia chromosome-positive CML patient who developed resistance to imatinib. Quantitative reverse transcription-polymerase chain reaction testing revealed a V280G BCR-ABL mutation.

DISCUSSION AND CONCLUSIONS

This is the first report describing a new BCR-ABL kinase domain mutation-V280G-that might be associated with resistance to imatinib. Approximately 15% to 30% of patients treated with imatinib discontinue treatment due to resistance or intolerance. More than 90 BCR-ABL mutations were detected so far, conferring variable degrees of drug resistance, with consequent clinical, therapeutic, and prognostic impact.

Tyrosine kinase inhibitors in chronic myeloid leukaemia: which, when, for whom?

The therapeutic armamentarium for chronic myeloid leukaemia (CML) comprises mainly tyrosine kinase inhibitors (TKIs), with several agents available for frontline treatment, or for the treatment of disease resistance or intolerance to the first-choice or second-choice drug. The availability of different drugs is a major achievement, but means that choices must be made - which can be difficult and questionable at times. The most important end point considered in decision-making regarding treatment for any cancer is overall survival, but additional factors (such as age, prognostic category, safety, or the possibility of achieving treatment-free remission) should be considered when selecting an agent for frontline treatment. Regardless of the TKI selected for first-line treatment, guidelines that define the importance of reaching specific response indicators and procedures for vigilant follow-up monitoring are established to ensure timely implementation of second-line TKIs. Herein, we discuss the benefits and risks of the different TKIs available for the treatment of patients with CML, and how to decide when to employ these agents at different treatment settings.

Chronic Myeloid Leukemia--Prognostic Value of Mutations

Chronic myeloid leukemia (CML) is a stem cell disorder characterized by unrestricted proliferation of the myeloid series that occurs due to the BCR-ABL fusion oncogene as a result of reciprocal translocation t(9;22) (q34;q11). This discovery has made this particular domain a target for future efforts to cure CML. Imatinib revolutionized the treatment options for CML and gave encouraging results both in case of safety as well as tolerability profile as compared to agents such as hydroxyurea or busulfan given before Imatinib. However, about 2-4% of patients show resistance and mutations have been found to be one of the reasons for its development. European Leukemianet gives recommendations for BCR-ABL mutational analysis along with other tyrosine kinase inhibitors (TKIs) that should be administered according to the mutations harbored in a patient. The following overview gives recommendations for monitoring patients on the basis of their mutational status.

Imatinib and Nilotinib increase glioblastoma cell invasion via Abl-independent stimulation of p130Cas and FAK signalling

Imatinib was the first targeted tyrosine kinase inhibitor to be approved for clinical use, and remains first-line therapy for Philadelphia chromosome (Ph+)-positive chronic myelogenous leukaemia. We show that treatment of human glioblastoma multiforme (GBM) tumour cells with imatinib and the closely-related drug, nilotinib, strikingly increases tyrosine phosphorylation of p130Cas, focal adhesion kinase (FAK) and the downstream adaptor protein paxillin (PXN), resulting in enhanced cell migration and invasion. Imatinib and nilotinib-induced tyrosine phosphorylation was dependent on expression of p130Cas and FAK activity and was independent of known imatinib targets including Abl, platelet derived growth factor receptor beta (PDGFRβ) and the collagen receptor DDR1. Imatinib and nilotinib treatment increased two dimensional cell migration and three dimensional radial spheroid invasion in collagen. In addition, silencing of p130Cas and inhibition of FAK activity both strongly reduced imatinib and nilotinib stimulated invasion. Importantly, imatinib and nilotinib increased tyrosine phosphorylation of p130Cas, FAK, PXN and radial spheroid invasion in stem cell lines isolated from human glioma biopsies. These findings identify a novel mechanism of action in GBM cells for two well established front line therapies for cancer resulting in enhanced tumour cell motility.

Novel drug therapies in myeloid leukemia: a patent review

Both acute myeloid leukemia and chronic myeloid leukemia are thought to arise from a subpopulation of primitive cells, termed leukemic stem cells that share properties with somatic stem cells. Leukemic stem cells are capable of continued self-renewal, and are resistant to conventional chemotherapy and are considered to be responsible for disease relapse. In recent years, improved understanding of the underlying mechanisms of myeloid leukemia biology has led to the development of novel and targeted therapies. This review focuses on clinically relevant patent applications and their relevance within the known literature in two areas of prevailing therapeutic interest, namely monoclonal antibody therapy and small molecule inhibitors in disease-relevant signaling pathways.

Factors influencing adherence to imatinib in Indian chronic myeloid leukemia patients: a cross-sectional study

Adherence to imatinib(IM) is of utmost importance in patients with chronic myeloid leukemia (CML) to maximise treatment effectiveness. The main objective is to measure adherence to IM by evaluating individual patient characteristics, personal behaviour and, treatment related psychological factors influencing adherence behaviour. Hundred patients receiving IM were analysed for adherence behaviour using 9 item Morisky Medication Adherence Scale (9-MMAS). Various factors were assessed for their impact on adherence behaviour. These factors were age, gender, duration of treatment, frequency and dosing of treatment, use of tobacco and alcohol, educational qualification, employment status, monthly income, side effects, financial assistance in treatment, social support, knowledge about medicine and disease, concomitant drug burden, polypharmacy, physician patient interaction, patient educational sessions and prevalence of depression. Seventy five percent of patients were found to be adherent. On univariate analysis, prevalence of depression (p<0.000001), moderate severe depression (p<0.000001), concomitant drug burden (p=0.036) and monthly income (p=0.015) were found to be significantly influencing adherence. The final multivariate model retained prevalence of depression with OR= 10.367 (95% CI, 3.112–34.538) as independent predictor of adherence to therapy. This study suggests that identification and treatment of depression among CML patients may further enhance adherence to IM therapy.

ABCB1 haplotypes but not individual SNPs predict for optimal response/failure in Egyptian patients with chronic-phase chronic myeloid leukemia receiving imatinib mesylate

Imatinib mesylate (IM) has so far been the standard of care for treating chronic myeloid leukemia (CML), but the initial striking efficacy of this drug has been overshadowed by the development of clinical resistance, which may in part be caused by pharmacogenetic variability. The ATP-binding cassette, subfamily B, member 1 (ABCB1) gene codes for P-glycoprotein (P-gp), a membrane-bound efflux transporter known to affect the pharmacokinetics of many drugs. IM is a substrate of the P-gp-mediated efflux. ABCB1 single nucleotide polymorphisms (SNPs) have been reported as modulators of ABCB1-mediated transport, affecting IM's bioavailability and consequently the treatment outcome of IM therapy. We aimed to examine the association between ABCB1 SNPs and the likelihood of achieving optimal response in IM-treated CML patients. Three ABCB1 SNPs (C1236T, G2677T, and C3435T) were genotyped in 100 Egyptian patients with CML undergoing IM therapy using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay. The optimal response rate did not differ significantly between C1236T, G2677T, or C3435T genotypes (P > 0.05). Optimal response rate was significantly different among patients with the CGC, TTT, TGC, CGT, TGT, CTC, CTT, and TTC haplotypes (P = 0.023). The 1236T-2677G-3435T haplotype was significantly associated with lower probability of achieving optimal response (P = 0.001). ABCB1 SNPs haplotype analysis should be taken into account in an attempt to get clearer insights into who is likely to respond optimally to IM for identifying CML patients who may not respond optimally to standard-dose IM therapy and potentially need an individualized therapeutic approach.

Interferon alfa versus interferon alfa plus cytarabine combination therapy for chronic myeloid leukemia: a meta-analysis of randomized controlled trials

OBJECTIVE

This article compares the effect of interferon alfa plus cytarabine (IFN-alfa + Ara-C) versus IFN-alfa alone on the chronic phase of chronic myelogenous leukemia.

METHODS

Electronic searches were performed in the Cochrane Central Register of Controlled Trials, PubMed, EMBASE, Chinese Biomedical Database, China Journal Full-text Database, and Chinese Scientific Journals Database. The languages were limited to Chinese and English. Randomized controlled trials were selected by 2 investigators. Analyses were performed using RevMan 5.0 software.

RESULTS

A total of 3139 patients in 4 studies met the inclusion criteria. In those patients, complete hematologic response and cytogenetic responses showed significant improvements in favor of IFN-alfa + Ara-C, with complete hematologic response relative risk (RR) of 1.15 (95% CI, 1.09-1.21), complete cytogenetic response RR of 1.87 (95% CI, 1.47-2.38), partial cytogenetic response RR of 1.48 (95% CI, 1.25-1.75), and major cytogenetic response RR of 1.61 (95% CI, 1.42-1.83), respectively. The overall 3-year survival rate in the IFN-alfa + Ara-C group was 86% compared with 79% in the IFN-alfa group (RR = 1.09; 95% CI, 1.03-1.14). In the other 2 studies, 5-year overall survival was 69% compared with 63%, respectively (RR = 1.08; 95% CI, 1.01-1.15). However, IFN-alfa and Ara-C involved higher risk of hematologic toxicity, gastrointestinal adverse events, and severe mucositis compared with IFN-alfa monotherapy (RR = 2.63 [95% CI, 1.94-3.56); RR = 3.38 [95% CI, 2.28-5.00], and RR = 8.84 [95% CI, 3.82-20.46], respectively). Weight loss and skin rash were also observed more frequently in the combination treatment group (RR = 2.00 [95% CI, 1.47-2.73) and RR = 3.75 [95% CI, 2.13-6.59], respectively).

CONCLUSIONS

In patients with chronic myelogenous leukemia in the chronic phase, the combination of IFN-alfa + Ara-C demonstrated improved complete hematologic response, superior cytogenetic responses, and higher rates of 3- and 5-year survival than IFN-alfa alone. However, combination therapy is more likely to cause serious adverse effects. Well-designed studies will be required to determine the outcomes and adverse effects of the 2 drugs as treatment for patients with chronic myelogenous leukemia who cannot afford molecularly targeted drugs.

Paradoxical MAPK-activation in response to treatment with tyrosine kinase inhibitors in CML: flow cytometry loses track

BACKGROUND

Paradoxical activation of the MAP-kinases, ERK1, and ERK2 (ERK1/2) is observed in CML cell lines and primary CML patient cells treated with tyrosine kinase inhibitors (TKI) in vitro. The commonly accepted assumption is that activated ERK1/2 is key regulators of survival of leukemic cells treated with kinase inhibitors. Hence, paradoxical ERK1/2-activation may trigger resistance in vivo, which yet has to be shown. We therefore sought to establish a flow cytometric assay that enables us to measure paradoxical TKI-induced ERK1/2-activation on a single cell basis in primary CML cells.

METHODS

Side-by-side Western blot and intracellular flow cytometry (FCM) after in vitro exposure of cell lines and primary cells to nilotinib were performed. Detailed analysis of pre-analytical factors and the issue of compartmentalization of phosphorylated ERK1/2 by confocal laser scanning microscopy were performed.

RESULT

Results were conflicting in that pERK-activation was robustly detected in Western blot assays, but not when cells were analyzed by FCM despite well functioning positive and negative controls. This is in contrast to experiments on other targets such as phospho-CrkL, where also in our hands TKI-dependent inhibition of phosphorylation is trackable by both Western blot and FCM assays.

CONCLUSIONS

To our knowledge this is the first report of discordant results in phospho-protein analysis in TKI-treated cells analyzed by Western blot vs. FCM. We speculate that a substance specific interaction interferes with fluorescence dependent methods seeking to track phosphorylated ERK1/2 in TKI-treated cells.

A tale of two approaches: complementary mechanisms of cytotoxic and targeted therapy resistance may inform next-generation cancer treatments

Chemotherapy and molecularly targeted approaches represent two very different modes of cancer treatment and each is associated with unique benefits and limitations. Both types of therapy share the overarching limitation of the emergence of drug resistance, which prevents these drugs from eliciting lasting clinical benefit. This review will provide an overview of the various mechanisms of resistance to each of these classes of drugs and examples of drug combinations that have been tested clinically. This analysis supports the contention that understanding modes of resistance to both chemotherapy and molecularly targeted therapies may be very useful in selecting those drugs of each class that will have complementing mechanisms of sensitivity and thereby represent reasonable combination therapies.

The CRKL gene encoding an adaptor protein is amplified, overexpressed, and a possible therapeutic target in gastric cancer

Background

Genomic DNA amplification is a genetic factor involved in cancer, and some oncogenes, such as ERBB2, are highly amplified in gastric cancer. We searched for the possible amplification of other genes in gastric cancer.

Methods and Results

A genome-wide single nucleotide polymorphism microarray analysis was performed using three cell lines of differentiated gastric cancers, and 22 genes (including ERBB2) in five highly amplified chromosome regions (with a copy number of more than 6) were identified. Particular attention was paid to the CRKL gene, the product of which is an adaptor protein containing Src homology 2 and 3 (SH2/SH3) domains. An extremely high CRKL copy number was confirmed in the MKN74 gastric cancer cell line using fluorescence in situ hybridization (FISH), and a high level of CRKL expression was also observed in the cells. The RNA-interference-mediated knockdown of CRKL in MKN74 disclosed the ability of CRKL to upregulate gastric cell proliferation. An immunohistochemical analysis revealed that CRKL protein was overexpressed in 24.4% (88/360) of the primary gastric cancers that were analyzed. The CRKL copy number was also examined in 360 primary gastric cancers using a FISH analysis, and CRKL amplification was found to be associated with CRKL overexpression. Finally, we showed that MKN74 cells with CRKL amplification were responsive to the dual Src/BCR-ABL kinase inhibitor BMS354825, likely via the inhibition of CRKL phosphorylation, and that the proliferation of MKN74 cells was suppressed by treatment with a CRKL-targeting peptide.

Conclusion

These results suggested that CRKL protein is overexpressed in a subset of gastric cancers and is associated with CRKL amplification in gastric cancer. Furthermore, our results suggested that CRKL protein has the ability to regulate gastric cell proliferation and has the potential to serve as a molecular therapy target for gastric cancer.

Quantitative modeling of chronic myeloid leukemia: insights from radiobiology

Mathematical models of chronic myeloid leukemia (CML) cell population dynamics are being developed to improve CML understanding and treatment. We review such models in light of relevant findings from radiobiology, emphasizing 3 points. First, the CML models almost all assert that the latency time, from CML initiation to diagnosis, is at most ∼10 years. Meanwhile, current radiobiologic estimates, based on Japanese atomic bomb survivor data, indicate a substantially higher maximum, suggesting longer-term relapses and extra resistance mutations. Second, different CML models assume different numbers, between 400 and 10(6), of normal HSCs. Radiobiologic estimates favor values>10(6) for the number of normal cells (often assumed to be the HSCs) that are at risk for a CML-initiating BCR-ABL translocation. Moreover, there is some evidence for an HSC dead-band hypothesis, consistent with HSC numbers being very different across different healthy adults. Third, radiobiologists have found that sporadic (background, age-driven) chromosome translocation incidence increases with age during adulthood. BCR-ABL translocation incidence increasing with age would provide a hitherto underanalyzed contribution to observed background adult-onset CML incidence acceleration with age, and would cast some doubt on stage-number inferences from multistage carcinogenesis models in general.

Imatinib and beyond--targeting activated tyrosine kinases in myeloproliferative disorders

Tyrosine kinases (TKs) play a major role in cellular signal transduction. Deregulated TK activity has been observed in solid cancers and hematologic malignancies. Advances in the understanding of the oncogenic activation of TKs led to the identification of new kinase inhibitors with improved potency, specificity, and efficacy. With the advent of imatinib mesylate, a new era in the management of patients with BCR-ABL+ chronic myelogenous leukemia (CML), gastrointestinal stromal tumors, and myeloproliferative neoplasms including chronic myelomonocytic leukemia with PDGFRB gene rearrangements and hypereosinophilic syndrome has begun. CML represents a model for the rational design of TK inhibitors based on the insights into signal transduction pathways. In CML, treatment with imatinib led to an outstanding clinical efficacy with limited toxicity. In BCR-ABL-negative myeloproliferation, the finding of activating point mutations in JAK2 prompted the development of JAK inhibitors to target this activated pathway. Aberrations of epigenetically active genes are the latest finding in the pathogenesis of myeloproliferative disorders and will serve as another target for innovative therapies.

Nilotinib and MEK inhibitors induce synthetic lethality through paradoxical activation of RAF in drug-resistant chronic myeloid leukemia

We show that imatinib, nilotinib, and dasatinib possess weak off-target activity against RAF and, therefore, drive paradoxical activation of BRAF and CRAF in a RAS-dependent manner. Critically, because RAS is activated by BCR-ABL, in drug-resistant chronic myeloid leukemia (CML) cells, RAS activity persists in the presence of these drugs, driving paradoxical activation of BRAF, CRAF, MEK, and ERK, and leading to an unexpected dependency on the pathway. Consequently, nilotinib synergizes with MEK inhibitors to kill drug-resistant CML cells and block tumor growth in mice. Thus, we show that imatinib, nilotinib, and dasatinib drive paradoxical RAF/MEK/ERK pathway activation and have uncovered a synthetic lethal interaction that can be used to kill drug-resistant CML cells in vitro and in vivo.

Role of tyrosine kinase inhibitors in the management of Philadelphia chromosome-positive acute lymphoblastic leukemia

The Philadelphia chromosome is the most common cytogenetic abnormality found in adult patients diagnosed with acute lymphoblastic leukemia. The result of this abnormality is the BCR-ABL protein, a constitutively active kinase involved in cell signaling and survival. When managed with multiagent chemotherapy regimens alone, patients have traditionally had an inferior outcome in terms of remission duration and overall survival when compared with patients who are Philadelphia chromosome-negative. Small-molecule tyrosine kinase inhibitors, such as imatinib and dasatinib, directly inhibit the BCR-ABL kinase, offering a targeted approach as a therapeutic option. As a result of several clinical trials with adequate follow-up, imatinib combined with chemotherapy represents the current standard of care for patients with newly diagnosed disease. Allogeneic stem cell transplantation has previously been the only modality to offer the potential for a cure, and it still should be considered for all patients deemed able to tolerate such an intervention. Second-generation tyrosine kinase inhibitors, such as dasatinib, may further improve the outcome in these patients. The role of molecular monitoring and the use of tyrosine kinase inhibitors after stem cell transplantation are areas of active investigation, and the results of ongoing trials will help to clarify the optimal management of these patients.

Disruption of Bcr-Abl coiled coil oligomerization by design

Oligomerization is an important regulatory mechanism for many proteins, including oncoproteins and other pathogenic proteins. The oncoprotein Bcr-Abl relies on oligomerization via its coiled coil domain for its kinase activity, suggesting that a designed coiled coil domain with enhanced binding to Bcr-Abl and reduced self-oligomerization would be therapeutically useful. Key mutations in the coiled coil domain of Bcr-Abl were identified that reduce homo-oligomerization through intermolecular charge-charge repulsion yet increase interaction with the Bcr-Abl coiled coil through additional salt bridges, resulting in an enhanced ability to disrupt the oligomeric state of Bcr-Abl. The mutations were modeled computationally to optimize the design. Assays performed in vitro confirmed the validity and functionality of the optimal mutations, which were found to exhibit reduced homo-oligomerization and increased binding to the Bcr-Abl coiled coil domain. Introduction of the mutant coiled coil into K562 cells resulted in decreased phosphorylation of Bcr-Abl, reduced cell proliferation, and increased caspase-3/7 activity and DNA segmentation. Importantly, the mutant coiled coil domain was more efficacious than the wild type in all experiments performed. The improved inhibition of Bcr-Abl through oligomeric disruption resulting from this modified coiled coil domain represents a viable alternative to small molecule inhibitors for therapeutic intervention.

Nonadherence to imatinib adversely affects event free survival in chronic phase chronic myeloid leukemia

There is limited data on the impact of treatment interruptions due to nonadherence in patients with chronic phase chronic myeloid leukemia (CP-CML) treated with Imatinib. We looked at factors (including adherence to therapy) affecting the outcome in a large cohort of patients with CP-CML. All the 516 patients received Imatinib free-of-cost through a company sponsored scheme, which mandated regular three monthly visits for drug procurement. Data regarding the disease characteristics, adherence to treatment and outcomes, were obtained from patients records. Unwarranted interruption of treatment for more than 1 week was defined as nonadherence. With a median follow-up of 39 months, the estimated 5-year event free survival (EFS) was 70.8% (95%, CI = 63.3-78.3). Nearly one-third of the patients (29.6%) were found to be nonadherent at some point during their treatment. On univariate analysis, the factors adversely affecting the EFS were prolonged symptom duration before diagnosis, treatment with hydroxyurea for more than 1 month before start of Imatinib, and nonadherence to therapy. Only nonadherence was significant in multivariate analysis (HR1.6; P = 0.048). The 5-year EFS in adherent and nonadherent patients was 76.7% and 59.8% respectively (P = 0.011, log rank test). Nonadherent patients were less likely to achieve complete cytogenetic responses (26% versus 44%; P = 0.004; χ(2) test) at any point. A significant proportion of patients with CP-CML have drug interruptions due to nonadherence during therapy and this compromises the EFS. Adherence to therapy must be included as an important evaluation parameter in all future studies of CML.

Factors influencing a second myeloid malignancy in patients with Philadelphia-negative -7 or del(7q) clones during tyrosine kinase inhibitor therapy for chronic myeloid leukemia

The detection of Philadelphia-negative (Ph(neg)) cells with non-random karyotypic abnormalities after tyrosine kinase inhibitor (TKI) therapy of chronic myeloid leukaemia (CML) can be associated with myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML). To our knowledge, however, there have been no studies on variables influencing the risk of MDS/AML in patients with specific Ph(neg) karyotypes. We systematically examined studies reporting -7 or del(7q) within Ph(neg) cells in TKI-treated CML patients, and abstracted clinical and cytogenetic data from individual reports into a standardized format for further analysis. Of 53 patients, 43 had Ph(neg) -7 clones [as the sole abnormality (-7(sole)) in 29, or with other clones (-7(dual)) in 14], and del(7q) was present in 10. A total of 16/51 evaluable patients, all with -7, transformed to MDS/AML. Transformation was more frequent (15/16 patients) within 6 months of Ph(neg) -7 detection rather than subsequently (P < 0.0001). At first detection after TKI therapy, Ph(neg) abnormal clones comprised ≥50% of Ph(neg) cells in a greater proportion of patients with -7 than del(7q) (P = 0.035). Upon comparing -7(sole) and -7(dual), the latter was likely to be transient (P = 0.004), and AML was frequently observed with persistent -7 clones (P = 0.03). By logistic regression analysis (n = 36), clone size (P = 0.017), time-to-detection longer than 15 months (P = 0.02), and CML response (P = 0.085) were associated with MDS/AML. Validation of these novel associations in registry-based studies will help develop predictive criteria that define the MDS/AML risk in individual patients.

Chromosome 20q deletion: a recurrent cytogenetic abnormality in patients with chronic myelogenous leukemia in remission

del(20q) can be observed in hematologic neoplasms, including chronic myelogenous leukemia (CML), and has been reported in patients undergoing blast transformation. We describe 10 patients with CML in hematologic and cytogenetic remission with del(20q) detected by conventional cytogenetics. There were 6 men and 4 women with a median age of 56 years. All patients initially had BCR-ABL1 and t(9;22) (q34;q11.2) and achieved morphologic and cytogenetic remission after therapy. del(20q) was identified before (2/10 [20%]), at the time of (3/10 [30%]), or after (5/10 [50%]) cytogenetic remission and was not associated with morphologic evidence of dysplasia. At last follow-up, no patients had a myelodysplastic syndrome (MDS). Leukocyte and platelet counts were normal; 4 of 10 patients had mild anemia. Nine patients have remained in morphologic and cytogenetic remission with stable del(20q). BCR-ABL1 fusion transcript levels were absent or low (median, 0.01%). Recently, in 1 patient, recurrent CML developed and del(20q) was lost. We conclude that del(20q) in the setting of CML in remission is not predictive of MDS or blast transformation.

Targeted signal transduction therapies in myeloid malignancies

The myeloid malignancies include the myeloproliferative neoplasms (MPN) including chronic myeloid leukemia (CML), and acute myeloid leukemia (AML). A growing body of evidence documents that these diseases are caused by genetic mutations that constitutively activate tyrosine kinases. They include the BCR/ABL in CML, the V617F JAK2 in Philadelphia chromosome-negative MPN, and the Flt3 ITD and TKD mutations in AML. Trials of the ABL kinase inhibitor, imatinib, have revolutionized the treatment of CML, and there are ongoing studies with other kinase inhibitors in MPN and AML. Here we review results of recent studies with first-generation JAK2 inhibitors in the treatment of MPN and second-generation ABL and Flt3 inhibitors in CML and AML, respectively. It is becoming apparent that although these kinase mutations have similar effects in vitro, each of the diseases has unique features that alter the use of kinase inhibitors in the clinic.

Therapeutic Targeting of Myc

Protein-protein interactions between members of the Myc transcription factor network are potential targets of small molecule inhibitors and stabilizers. Diverse screening strategies, including fluorescence resonance energy transfer, fluorescence polarization, two hybrid and protein complementation assays have identified several lead compounds that inhibit Myc-Max dimerization and one compound that stabilizes the Max homodimer. Representative compounds interfere with Myc-induced transcriptional activation, Myc-mediated oncogenic transformation, Myc-driven cellular replication and DNA binding of Myc. For the best characterized compounds, specific binding sites have been determined, and molecular mechanisms of action have been documented. This knowledge of small molecule - protein interaction is currently applied to highly targeted approaches that seek to identify novel compounds with improved potency.