Mechanisms of clinical resistance to small molecule tyrosine kinase inhibitors targeting oncogenic tyrosine kinases.
ABSTRACT A number of highly specific small molecule inhibitors of oncogenic tyrosine kinases have been developed and may potentially improve the treatment of different malignant diseases. However, it became rapidly evident that multiple resistance mechanisms compromise the successful clinical application of these inhibitors, particularly in advanced solid tumors. To develop efficient therapeutic strategies with small molecule inhibitors, one must understand the causes for treatment failure. Three different types of resistance to small molecule inhibitors of oncogenic tyrosine kinases have been observed. The malignant phenotype may be independent of the activity of the target kinase (target-independent resistance). Alternatively, overexpression or mutation of the target kinase can counteract the inhibition of oncogenic tyrosine kinases (target-dependent resistance). Finally, alterations of drug transporters or drug-metabolizing pathways may block the bioavailability of the tyrosine kinase inhibitors (drug-dependent resistance). This article reviews the current knowledge of clinical resistance to small molecule inhibitors approved for treatment of cancer patients.
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ABSTRACT: Combining targeted therapy has been extensively investigated in previously treated advanced non-small-cell lung cancer (NSCLC), but it is still unclear whether combining targeted therapy might offer any benefits against standard monotherapy with erlotinib. We thus performed a meta-analysis of randomized controlled trials to compare the efficacy and safety of combining targeted therapy versus erlotinib alone as second-line treatment for advanced NSCLC. Several databases were searched, including Pubmed, Embase and Cochrane databases. The endpoints were overall survival (OS), progression-free survival (PFS), overall response rate (ORR) and grade 3 or 4 adverse event (AEs). The pooled hazard ratio (HR) or odds ratio (OR), and 95% confidence intervals (CI) were calculated employing fixed- or random-effects models depending on the heterogeneity of the included trials. Eight eligible trials involved 2417 patients were ultimately identified. The intention to treatment (ITT) analysis demonstrated that combining targeted therapy significantly improved OS (HR 0.90, 95%CI: 0.82-0.99, p = 0.024), PFS (HR 0.83, 95%CI: 0.72-0.97, p = 0.018), and ORR (OR 1.35, 95%CI 1.01-1.80, P = 0.04). Sub-group analysis based on phases of trials, EGFR-status and KRAS status also showed that there was a tendency to improve PFS and OS in combining targeted therapy, except that PFS for patients with EGFR-mutation or wild type KRAS favored erlotinib monotherapy. Additionally, more incidence of grade 3 or 4 rash, fatigue and hypertension were observed in combining targeted therapy. With the available evidence, combining targeted therapy seems superior over erlotinib monotherapy as second-line treatment for advanced NSCLC. More studies are still needed to identify patients who will most likely benefit from the appropriate combining targeted therapy.PLoS ONE 01/2013; 8(2):e55637. · 3.73 Impact Factor
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ABSTRACT: Head and neck cancer constitutes the 6th most common malignancy worldwide and affects the crucial anatomical structures and physiological functions of the upper aerodigestive tract. Classical therapeutic strategies such as surgery and radiotherapy carry substantial toxicity and functional impairment. Moreover, the loco-regional control rates as well as overall survival still need to be improved in subgroups of patients. The scatter-factor/hepatocyte growth factor receptor tyrosine kinase MET is an established effector in the promotion, maintenance and progression of malignant transformation in a wide range of human malignancies, and has been gaining considerable interest in head and neck cancer over the last 15years. Aberrant MET activation due to overexpression, mutations, tumor-stromal paracrine loops, and cooperative/redundant signaling has been shown to play prominent roles in epithelial-to-mesenchymal transition, angiogenesis, and responses to anti-cancer therapeutic modalities. Accumulating preclinical and translational evidence highly supports the increasing interest of MET as a biomarker for lymph node and distant metastases, as well as a potential marker of stratification for responses to ionizing radiation. The relevance of MET as a therapeutic molecular target in head and neck cancer described in preclinical studies remains largely under-evaluated in clinical trials, and therefore inconclusive. Also in the context of anti-cancer targeted therapy, a large body of preclinical data suggests a central role for MET in treatment resistance towards multiple therapeutic modalities in malignancies of the head and neck region. These findings, as well as the potential use of combination therapies including MET inhibitors in these tumors, need to be further explored.Pharmacology [?] Therapeutics 04/2014; · 7.79 Impact Factor
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ABSTRACT: A detailed understanding of the mechanisms by which tumors acquire resistance to targeted anticancer agents should speed the development of treatment strategies with lasting clinical efficacy. RAF inhibition in BRAF-mutant melanoma exemplifies the promise and challenge of many targeted drugs; although response rates are high, resistance invariably develops. Here, we articulate overarching principles of resistance to kinase inhibitors, as well as a translational approach to characterize resistance in the clinical setting through tumor mutation profiling. As a proof of principle, we performed targeted, massively parallel sequencing of 138 cancer genes in a tumor obtained from a patient with melanoma who developed resistance to PLX4032 after an initial dramatic response. The resulting profile identified an activating mutation at codon 121 in the downstream kinase MEK1 that was absent in the corresponding pretreatment tumor. The MEK1(C121S) mutation was shown to increase kinase activity and confer robust resistance to both RAF and MEK inhibition in vitro. Thus, MEK1(C121S) or functionally similar mutations are predicted to confer resistance to combined MEK/RAF inhibition. These results provide an instructive framework for assessing mechanisms of acquired resistance to kinase inhibition and illustrate the use of emerging technologies in a manner that may accelerate personalized cancer medicine.Journal of Clinical Oncology 03/2011; 29(22):3085-96. · 18.04 Impact Factor