Pharmacogenomic and pharmacokinetic determinants of erlotinib toxicity

Exploiting Host Kinases to Combat Dengue Virus Infection and Disease

The burden of dengue on human health has dramatically increased in recent years, underscoring the urgent need for effective therapeutic interventions. Despite decades of research since the discovery of the dengue virus, no specific antiviral treatments are available and strategies to reliably prevent severe disease remain limited. Direct-acting antivirals against dengue are under active investigation but have shown limited efficacy to date. An underappreciated Achille's heal of the virus is its dependence on host factors for infection and pathogenesis, each of which presents a potential avenue for therapeutic intervention. We and others have demonstrated that dengue virus relies on multiple host kinases, some of which are already targeted by clinically approved inhibitors. These offer drug repurposing opportunities for host-directed dengue treatment. Here, we summarize findings on the role of kinases in dengue infection and disease and highlight potential kinase targets for the development of innovative host-directed therapeutics.

Efficacy in patients with EGFR-positive non-small-cell lung cancer treated with dacomitinib who had skin adverse events: post hoc analyses from ARCHER 1050

Aim: We investigated association between skin adverse events (AEs) and efficacy with dacomitinib in patients with EGFR-positive non-small-cell lung cancer (NSCLC).Methods: Post hoc analyses from ARCHER 1050 evaluated efficacy in patients who did and did not experience grade ≥2 skin AEs with dacomitinib. Landmark analyses were performed at 3 and 6 months.Results: In patients who had skin AEs (72.2%) vs. those who did not (27.7%), median progression-free survival was 16.0 vs. 9.2 months, median overall survival (OS) was 37.7 vs. 21.6 months, and objective response rate was 80.2 vs. 61.5%; OS was improved at 3 and 6 months landmark analyses.Conclusion: Presence of grade ≥2 skin AEs was associated with numerically improved efficacy and represents a valuable biomarker of treatment outcome with dacomitinib in patients with advanced NSCLC.Clinical Trial Registration: NCT01774721 (ClinicalTrials.gov).

Loss of copy numbers of retrotransposons (HERVK) on chromosome 7p11.2 impacts EGFR (Epidermal Growth Factor Receptor)-induced phenotypes for platinum sensitivity and long-term survival in ovarian cancer-A study from the OVCAD consortium

We analyzed variations in the epidermal growth factor receptor (EGFR) gene and 5'-upstream region to identify potential molecular predictors of treatment response in primary epithelial ovarian cancer. Tumor tissues collected during debulking surgery from the prospective multicenter OVCAD study were investigated. Copy number variations in the human endogenous retrovirus sequence human endogenous retrovirus K9 (HERVK9) and EGFR Exons 7 and 9, as well as repeat length and loss of heterozygosity of polymorphic CA-SSR I and relative EGFR mRNA expression were determined quantitatively. At least one EGFR variation was observed in 94% of the patients. Among the 30 combinations of variations discovered, enhanced platinum sensitivity (n = 151) was found dominantly with HERVK9 haploidy and Exon 7 tetraploidy, overrepresented among patients with survival ≥120 months (24/29, p = .0212). EGFR overexpression (≥80 percentile) was significantly less likely in the responders (17% vs. 32%, p = .044). Multivariate Cox regression analysis, including age, FIGO stage, and grade, indicated that the patients' subgroup was prognostically significant for CA-SSR I repeat length <18 CA for both alleles (HR 0.276, 95% confidence interval 0.109-0.655, p = .001). Although EGFR variations occur in ovarian cancer, the mRNA levels remain low compared to other EGFR-mutated cancers. Notably, the inherited length of the CA-SSR I repeat, HERVK9 haploidy, and Exon 7 tetraploidy conferred three times higher odds ratio to survive for more than 10 years under therapy. This may add value in guiding therapies if determined during follow-up in circulating tumor cells or circulating tumor DNA and offers HERVK9 as a potential therapeutic target.

Toxicity Profile of eBAT, a Bispecific Ligand-Targeted Toxin Directed to EGFR and uPAR, in Mice and a Clinical Dog Model

EGFR-targeted therapies are efficacious, but toxicity is common and can be severe. Urokinase type plasminogen activator receptor (uPAR)-targeted drugs are only emerging, so neither their efficacy nor toxicity is fully established. Recombinant eBAT was created by combining cytokines EGF and uPA on the same single-chain molecule with truncated Pseudomonas toxin. Its purpose was to simultaneously target tumors and their vasculature in the tumor microenvironment. In prior studies on mice and dogs, the drug proved efficacious. Here, we report the safety of eBAT in normal wildtype, uPAR knockout, and immunoreplete and immunodeficient tumor-bearing mice, as well as in dogs with spontaneous sarcoma that more closely mirror human cancer onset. In immunocompetent mice, tumor-bearing mice, uPAR knockout mice, and mice receiving species-optimized eBAT, toxicities were mild and self-limiting. Likewise, in dogs with life-threatening sarcoma given dosages found to be biologically active, eBAT was well tolerated. In mice receiving higher doses, eBAT was associated with dose-dependent evidence of liver injury, including portal biliary hyperplasia, oval cell proliferation, lymphoplasmacytic inflammation, periportal hepatocellular microvesicular change, hemorrhage, necrosis, and apoptosis. The results support continuing the clinical development of eBAT as a therapeutic agent for individuals with sarcoma and other cancers.

Tyrosine kinase inhibitors in cancers: Treatment optimization - Part II

Real-life populations are more heterogeneous than those included in prospective clinical studies. In cancer patients, comorbidities and co-medications favor the appearance of severe adverse effects which can significantly impact quality of life and treatment effectiveness. Most of tyrosine kinase inhibitors (TKI) have been developed with flat oral dosing exposing patients to the risk of poor adherence due to side effects. Additionally, genetic or physiological factors, differences in diet, and drug-drug interactions can lead to inter-individual variability affecting treatment outcomes and increasing the risk of adverse events. Knowledge of the different factors of variability allows individualized patient management. This review examines the effects of adherence, food intake, and pharmaceutical form on the pharmacokinetics of oral TKI, as well as evaluating pharmacokinetics considerations improving TKI management. Concentration-effectiveness and concentration-toxicity data are presented for the selected TKI, and a simple therapeutic drug monitoring schema is outlined to help individualize dosing of oral TKI.

In Vitro evaluation of the anti-pancreatic cancer activity of epimedium herb

Introduction: Pancreatic cancer (PC) is a particularly aggressive malignancy with limited therapeutic options. The search for innovative treatments has focused on traditional Chinese medicine, specifically epimedium. This research investigates epimedium's active ingredients, potential targets, and underlying mechanisms in treating PC. Methods: High-performance liquid chromatography (HPLC) was used to quantify the active components of epimedium and HPLC-Q-TOF-MS was employed for qualitative identification. Potential targets of epimedium's active ingredients were identified using the TCMSP, ETCM, CTD, and Swiss Target Prediction databases. Potential PC-related targets were sourced from DisGeNET, GeneCards, and OMIM databases. A Venn diagram was utilized to identify overlapping PC-related and epimedium targets. Core targets and pathways were elucidated through protein-protein interaction (PPI) network analysis, Gene Ontology (GO) assessments, and Reactome pathway enrichment analyses. Molecular docking techniques investigated interactions between active compounds and these targets. The expression and prognostic implications of target genes were evaluated using GEPIA2 and the Human Protein Atlas (HPA) databases. In vitro studies assessed the impact of epimedium extract (EPE) on Panc-1 cell viability, and Western blot analysis examined the expression levels of key targets. Results: Network pharmacological indicate that epimedium econtains active components such as baohuoside I, icariin, hyperoside, and epimedin B, which have potential therapeutic effects against PC. In vitro assays confirmed that EPE significantly reduced the viability of Panc-1 cells. Western blot analysis revealed a considerable decrease in the expression of key targets in EPE-treated cells, including AKT1, EGFR, p-EGFR, JUN, BCL2, IL6, and SRC. The R-HSA-1280215: Interleukin-4 and Interleukin-13 signaling pathways involving these genes were identified as potential therapeutic targets. Discussion: Epimedium holds promise as a candidate for treating PC. The modulation of interleukin-4 and interleukin-13 signaling pathways could be a pivotal mechanism by which epimedium impedes tumor development. Further research is warranted to validate these findings and explore the clinical applicability of epimedium in PC treatment.

Development and validation of HPLC method for simultaneous estimation of erlotinib and niclosamide from liposomes optimized by screening design

The emerging drug resistance to the approved first-line drug therapy leads to clinical failure in cancer. Drug repurposing studies lead to the identification of many old drugs to be used for cancer treatment. Combining the repurposed drugs (niclosamide) with first-line therapy agents like erlotinib HCl showed improved efficacy by inhibiting erlotinib HCl acquired resistance. But there is a need to develop a sensitive, accurate, and excellent analytical method and drug delivery system for successfully delivering drug combinations. In the current study, an HPLC method was developed and validated for the simultaneous estimation of niclosamide and erlotinib HCl. The retention time of niclosamide and erlotinib hydrochloride was 6.48 and 7.65 min at 333 nm. The developed method was rapid and sensitive to separating the two drugs with reasonable accuracy, precision, robustness, and ruggedness. A Plackett-Burman (PBD) screening design was used to identify the critical parameters affecting liposomal formulation development using particle size, size distribution, zeta potential, and entrapment efficiency as the response. Lipid concentration, drug concentration, hydration temperature, and media volume were critical parameters affecting the particle size, polydispersity index (PDI), ZP, and %EE of the liposomes. The optimized NCM-ERL liposomes showed the particle size (126.05 ± 2.1), PDI (0.498 ± 0.1), ZP (-16.2 ± 0.3), and %EE of NCM and ERL (50.04 ± 2.8 and 05.42 ± 1.3). In vitro release studies indicated the controlled release of the drugs loaded liposomes (87.06 ± 9.93% and 42.33 ± 0.89% in 24 h).

Activation/Inactivation of Anticancer Drugs by CYP3A4: Influencing Factors for Personalized Cancer Therapy

Cytochrome P450 3A4 (CYP3A4), one of the most important members of the cytochrome P450 subfamily, is a crucial catalyst in the metabolism of numerous drugs. As it catalyzes numerous processes for drug activation or inactivation, the pharmacological activities and clinical outcomes of anticancer drugs metabolized by CYP3A4 are highly dependent on the enzyme's activity and expression. Due to the complexity of tumor microenvironments and various influencing factors observed in human in vitro models and clinical studies, the pharmacokinetics of most anticancer drugs are influenced by the extent of induction or inhibition of CYP3A4-mediated metabolism, and these details are not fully recognized and highlighted. Therefore, this interindividual variability due to genetic and nongenetic factors, together with the narrow therapeutic index of most anticancer drugs, contributes to their unique set of exposures and responses, which have important implications for achieving the expected efficacy and minimizing adverse events of chemotherapy for cancer in individuals. To elucidate the mechanisms of CYP3A4-mediated activation/inactivation of anticancer drugs associated with personalized therapy, this review focuses on the underlying determinants that contribute to differences in CYP3A4 metabolic activity and provides a comprehensive and valuable overview of the significance of these factors, which differs from current considerations for dosing regimens in cancer therapy. We also discuss knowledge gaps, challenges, and opportunities to explore optimal dosing regimens for drug metabolic activation/inactivation in individual patients, with particular emphasis on pooling and analyzing clinical information that affects CYP3A4 activity. SIGNIFICANCE STATEMENT: This review focuses on anticancer drugs that are activated/deactivated by CYP3A4 and highlights outstanding factors affecting the interindividual variability of CYP3A4 activity in order to gain a detailed understanding of CYP3A4-mediated drug metabolism mechanisms. A systematic analysis of available information on the underlying genetic and nongenetic determinants leading to variation in CYP3A4 metabolic activity to predict therapeutic response to drug exposure, maximize efficacy, and avoid unpredictable adverse events has clinical implications for the identification and development of CYP3A4-targeted cancer therapeutics.

Comparison of Plasma Metabolites From Patients With Non-Small Cell Lung Cancer by Erlotinib Treatment and Skin Rash

Erlotinib is a necessary anticancer treatment for non-small cell lung cancer (NSCLC) patients yet it causes severe side effects such as skin rash. In this study, researchers compared the untargeted compound profiles before and after erlotinib administration to observe changes in blood metabolites in NSCLC patients. The levels of 1005 substances changed after taking erlotinib. The levels of 306 and 699 metabolites were found to have increased and decreased, respectively. We found 5539 substances with peak area differences based on the presence of skin rash. Carbohydrate, amino acid, and vitamin metabolic pathways were altered in response to the onset of erlotinib-induced skin rash. Finally, this study proposed using plasma metabolites to identify biomarker(s) induced by erlotinib, as well as target molecule(s), for the treatment of dermatological toxic effects.

Side effects of tyrosine kinase inhibitors therapy in patients with non-small cell lung cancer and associations with EGFR polymorphisms: A systematic review and meta-analysis

Rash and diarrhea are common side effects of tyrosine kinase inhibitor (TKI) therapy administered to patients with non-small cell lung cancer (NSCLC). The polymorphisms of the epidermal growth factor receptor (EGFR) gene may be a potential predictor of these side effects. The aim of the present meta-analysis was to examine the association of EGFR polymorphisms and TKI-associated toxicities. Electronic databases (PubMed, Scopus and ISI Web of Science) were searched for relevant studies. According to the inclusion and exclusion criteria, a search of the databases identified 4,918 results, among which 6 clinical trials were obtained with 1,318 patients with NSCLC. A total of 9 EGFR single nucleotide polymorphisms (SNPs) associated with TKI toxicity were identified including, rs11568315, rs712829, rs712830, rs2227983, rs2075102, rs2293347, rs11977388, rs4947492 and rs884225. The data associated with skin toxicity from rs11568315, rs712829 and rs712830 were analyzed in the present meta-analysis. Data from rs11568315 were also analyzed in relation to diarrhea. Among all the examined SNPs, statistically significant results were obtained under the dominant genetic model for CA repeats in rs11568315 (SS vs. SL+LL) with skin toxicity. The long CA repeat (SL+LL) carriers were more likely to experience skin toxicity associated with TKIs (P=0.005). By contrast, there was no significant result for diarrhea (P=0.661) under dominant genetic model for CA repeats.

Deciphering the action mechanism of paeoniflorin in suppressing pancreatic cancer: A network pharmacology study and experimental validation

Background: Paeoniflorin (PF) is the main active component of Chinese herbaceous peony that has been shown to have an anti-tumor effect. However, there are few studies on the prevention and treatment of pancreatic cancer with PF.

Methods: We gathered Microarray data pertaining to paeoniflorin intervention in pancreatic cancer by utilizing the GEO database (GSE97124). Then, the DEGs were filtered by the 33R program. RNA-seq data of pancreatic cancer and normal tissue samples were taken from the TCGA and GTEx databases, respectively, and the WGCNA technique was utilized to examine the pancreatic cancer-specific genes. Paeoniflorin target genes for the treatment of pancreatic cancer were determined based on the overlap between DEGs and WGCNA. GO and KEGG enrichment analyses were then performed on paeoniflorin target genes to discover which biological processes were impacted. Using the 3 hierarchical methods included in the Cytohubba plugin, we re-screened the hub genes in the target genes to find the genes most relevant to paeoniflorin treatment. The overall survival effects of hub genes were confirmed using the TCGA database. Finally, the paeoniflorin targets identified by the network pharmacology analysis were validated using PANC-1 and Capan-2 cells.

Results: We identified 148 main potential PF targets, and gene enrichment analysis suggested that the aforementioned targets play a crucial role in the regulation of MAPK, PI3K-AKT, and other pathways. The further screening of the prospective targets resulted in the identification of 39 hub genes. Using the TCGA database, it was determined that around 33.33% of the hub gene’s high expression was linked with a bad prognosis. Finally, we demonstrated that PF inhibits IL-6 and IL-10 expression and p38 phosphorylation in pancreatic cancer cells, thereby reducing inflammation.

Conclusion: PF may regulate inflammatory factors mainly through the p38 MAPK signal pathway. These findings provide theoretical and experimental evidence suggesting the PF as a promising natural source of anti-tumor compounds for pancreatic cancer.

Relevance of Therapeutic Drug Monitoring of Tyrosine Kinase Inhibitors in Routine Clinical Practice: A Pilot Study

INTRODUCTION

The main goal of treatment in cancer patients is to achieve the highest therapeutic effectiveness with the least iatrogenic toxicity. Tyrosine kinase inhibitors (TKIs) are anticancer oral agents, usually administered at fixed doses, which present high inter- and intra-individual variability due to their pharmacokinetic characteristics. Therapeutic drug monitoring (TDM) can be used to optimize the use of several types of medication.

OBJECTIVE

We evaluated the use of TDM of TKIs in routine clinical practice through studying the variability in exposure to erlotinib, imatinib, lapatinib, and sorafenib and dose adjustment.

MATERIALS AND METHODS

We conducted a retrospective analytical study involving patients who received treatment with TKIs, guided by TDM and with subsequent recommendation of dose adjustment. The quantification of the plasma levels of the different drugs was performed using high-performance liquid chromatography (HPLC). The Clinical Research Ethics Committee of the Hospital Quirónsalud Torrevieja approved this study.

RESULTS

The inter-individual variability in the first cycle and in the last monitored cycle was 46.2% and 44.0% for erlotinib, 48.9 and 50.8% for imatinib, 60.7% and 56.0% for lapatinib and 89.7% and 72.5% for sorafenib. Relationships between exposure and baseline characteristics for erlotinib, imatinib, lapatinib and sorafenib were not statistically significant for any of the variables evaluated (weight, height, body surface area (BSA), age and sex). Relationships between height (p = 0.021) and BSA (p = 0.022) were statistically significant for sorafenib. No significant relationships were observed between C_trough and progression-free survival (PFS) or overall survival (OS) for any drug, except in the case of sunitinib (correlation between C_trough and PFS p = 0.023) in the exposure-efficacy analysis.

CONCLUSIONS

Erlotinib, imatinib, lapatinib and sorafenib show large inter-individual variability in exposure. TDM entails a significant improvement in exposure and enables more effective and safe use of TKIs in routine clinical practice.

Selective Immune Modulating Activities of Viscum album and Its Components; A Possibility of Therapeutics on Skin Rash Induced by EGFR Inhibitors

Viscum album var. coloratum (Kom.) Ohwi is a traditional herbal medicine used in East Asia to treat hypertension, skeletal muscle disorders, and cancer. The inhibitory effects of Viscum album (VA) extract on chemokines and its therapeutic potential in erlotinib-induced skin rash were investigated in this study. ELISA was used to measure the levels of chemokines, MCP-1 and RANTES, which are thought to be mediators of erlotinib-induced skin rash in RAW264.7 cells. Western blot analysis was used to look into the activation of signaling pathways like AKT, MAPK, and EGF. In order to investigate the active compounds in VA extract, solvent fractionation and preparative HPLC were performed sequentially. VA extract significantly reduced the production of TNF-α, MCP-1, and RANTES but not IL-1. Furthermore, macrophage transmigration was inhibited without causing cell toxicity. VA extract had no effect on the phosphorylation of EGF receptors stimulated by EGF or suppressed by erlotinib in both A549, a non-small cell lung cancer cells, and Hacat, a human skin keratinocyte. The isolated viscumneoside III and viscumneoside V from VA extract significantly suppressed the expression of MCP-1, according to activity guided fractionation with organic solvent fractionation and preparative HPLC. These findings suggest that VA extract and its active compounds, viscumneoside III and viscumneoside V, regulate MCP-1 production and may have the potential to suppress erlotinib-induced skin toxicity by modulating macrophage activity without neutralizing anti-cancer efficacy.

Multidrug efflux transporter ABCG2: expression and regulation

The adenosine triphosphate (ATP)-binding cassette efflux transporter G2 (ABCG2) was originally discovered in a multidrug-resistant breast cancer cell line. Studies in the past have expanded the understanding of its role in physiology, disease pathology and drug resistance. With a widely distributed expression across different cell types, ABCG2 plays a central role in ATP-dependent efflux of a vast range of endogenous and exogenous molecules, thereby maintaining cellular homeostasis and providing tissue protection against xenobiotic insults. However, ABCG2 expression is subjected to alterations under various pathophysiological conditions such as inflammation, infection, tissue injury, disease pathology and in response to xenobiotics and endobiotics. These changes may interfere with the bioavailability of therapeutic substrate drugs conferring drug resistance and in certain cases worsen the pathophysiological state aggravating its severity. Considering the crucial role of ABCG2 in normal physiology, therapeutic interventions directly targeting the transporter function may produce serious side effects. Therefore, modulation of transporter regulation instead of inhibiting the transporter itself will allow subtle changes in ABCG2 activity. This requires a thorough comprehension of diverse factors and complex signaling pathways (Kinases, Wnt/β-catenin, Sonic hedgehog) operating at multiple regulatory levels dictating ABCG2 expression and activity. This review features a background on the physiological role of transporter, factors that modulate ABCG2 levels and highlights various signaling pathways, molecular mechanisms and genetic polymorphisms in ABCG2 regulation. This understanding will aid in identifying potential molecular targets for therapeutic interventions to overcome ABCG2-mediated multidrug resistance (MDR) and to manage ABCG2-related pathophysiology.

Epidermal growth factor receptor inhibitor-induced diarrhea: clinical incidence, toxicological mechanism, and management

The epidermal growth factor receptor (EGFR) family is a class of receptor tyrosine kinase playing a central role in carcinogenesis and cancer progression. The members of this family, particularly EGFR and human epidermal growth factor receptor 2 (HER2), are the most extensively studied drug targets for malignancy. Today, numerous tyrosine kinase inhibitors targeting EGFR family have been developed to combat non-small-cell lung cancer and breast cancer. However, severe gastrointestinal (GI) toxicity leading to dose reduction and treatment discontinuation hampers the therapeutic outcome of EGFR inhibitors. Diarrhea is one of the most frequent GI side effects, especially when it comes to second-generation EGFR inhibitors. Enterocytes apoptosis and increased inflammation accompany with many oral EGFR inhibitors. Loperamide and budesonide are the first-line treatment to manage such adverse effects. However, current prophylaxis and management are all empirical interventions to relieve the symptom. They do not specifically target the toxicological mechanism of EGFR inhibitors. Hereby, those anti-diarrhea agents do not work well when used in cancer patients experiencing EGFR inhibitor-induced diarrhea. On the other hand, the toxicological mechanism of EGFR inhibitor-induced diarrhea is poorly understood. Thus, determining the mechanism behind such diarrhea is urgently in need for developing genuinely effective anti-diarrhea agents. This review aims to call attention to EGFR inhibitor-induced diarrhea, a highly occurring and devastating cancer drug toxicity.

Medically Important Alterations in Transport Function and Trafficking of ABCG2

Several polymorphisms and mutations in the human ABCG2 multidrug transporter result in reduced plasma membrane expression and/or diminished transport function. Since ABCG2 plays a pivotal role in uric acid clearance, its malfunction may lead to hyperuricemia and gout. On the other hand, ABCG2 residing in various barrier tissues is involved in the innate defense mechanisms of the body; thus, genetic alterations in ABCG2 may modify the absorption, distribution, excretion of potentially toxic endo- and exogenous substances. In turn, this can lead either to altered therapy responses or to drug-related toxic reactions. This paper reviews the various types of mutations and polymorphisms in ABCG2, as well as the ways how altered cellular processing, trafficking, and transport activity of the protein can contribute to phenotypic manifestations. In addition, the various methods used for the identification of the impairments in ABCG2 variants and the different approaches to correct these defects are overviewed.

ABCB1, ABCG2, ABCC1, ABCC2, and ABCC3 drug transporter polymorphisms and their impact on drug bioavailability: what is our current understanding?

INTRODUCTION

Interindividual differences in drug response are a frequent clinical challenge partly due to variation in pharmacokinetics. ATP-binding cassette (ABC) transporters are crucial determinants of drug disposition. They are subject of gene regulation and drug-interaction; however, it is still under debate to which extend genetic variants in these transporters contribute to interindividual variability of a wide range of drugs.

AREAS COVERED

This review discusses the current literature on the impact of genetic variants in ABCB1, ABCG2 as well as ABCC1, ABCC2, and ABCC3 on pharmacokinetics and drug response. The aim was to evaluate if results from recent studies would increase the evidence for potential clinically relevant pharmacogenetic effects.

EXPERT OPINION

Although enormous efforts have been made to investigate effects of ABC transporter genotypes on drug pharmacokinetics and response, the majority of studies showed only weak if any associations. Despite few unique results, studies mostly failed to confirm earlier findings or still remained inconsistent. The impact of genetic variants on drug bioavailability is only minor and other factors regulating the transporter expression and function seem to be more critical. In our opinion, the findings on the so far investigated genetic variants in ABC efflux transporters are not suitable as predictive biomarkers.

Impact of variants in ATP-binding cassette transporters on breast cancer treatment

There has been substantial interest in the impact of ATP-binding cassette (ABC) transporter variability on breast cancer drug resistance. Here, we provide a systematic review of ABC variants in breast cancer therapy. Notably, most studies used small heterogeneous cohorts and their identified associations lack statistical stringency, replication and mechanistic support. We conclude that commonly studied ABC polymorphisms are not suitable to accurately predict therapy response or toxicity in breast cancer patients and cannot guide treatment decisions. However, recent research shows that ABC transporters harbor a plethora of rare variants with individually small effect sizes, and we argue that a shift in strategy from target variant interrogation to comprehensive profiling might hold promise to drastically improve the predictive power of outcome models.

The ABCG2/BCRP transporter and its variants - from structure to pathology

The ABCG2 protein has a key role in the transport of a wide range of structurally dissimilar endo- and xenobiotics in the human body, especially in the tissue barriers and the metabolizing or secreting organs. The human ABCG2 gene harbors a high number of polymorphisms and mutations, which may significantly modulate its expression and function. Recent high-resolution structural data, complemented with molecular dynamic simulations, may significantly help to understand intramolecular movements and substrate handling, as well as the effects of mutations on the membrane transporter function of ABCG2. As reviewed here, structural alterations may result not only in direct alterations in drug binding and transporter activity, but also in improper folding or problems in the carefully regulated process of trafficking, including vesicular transport, endocytosis, recycling, and degradation. Here, we also review the clinical importance of altered ABCG2 expression and function in general drug metabolism, cancer multidrug resistance, and impaired uric acid excretion, leading to gout.

Phase II study evaluating the association of gemcitabine, trastuzumab and erlotinib as first-line treatment in patients with metastatic pancreatic adenocarcinoma (GATE 1)

In a previous phase II study (THERAPY), cetuximab and trastuzumab combination, as second-line after progression with gemcitabine, showed disease stabilization in 27% of 33 patients with pancreatic carcinoma. In the present phase II multicenter study, we assessed the efficacy and tolerance of gemcitabine, trastuzumab plus erlotinib as first-line treatment of metastatic pancreatic cancer. The primary endpoint was disease control rate (DCR, RECIST v.1); secondary endpoints were progression-free (PFS), overall (OS) survival and toxicity (NCI-CTCAE v3.0). Ancillary study addressed the predictive value of both EGFR/HER2 expression and KRAS mutational status. Sixty-three patients from four centers were included (62 evaluable for toxicity, 59 for efficacy), median age was 62 years (35-77), 59.7% men. The median treatment duration was 16.1 weeks (2.1-61). Eleven patients (19%) reported a partial tumor response, and 33 (56%) disease stabilization. DCR was 74.6% (95%CI: 61.8-85.0; 44/59 patients). After a median follow-up of 23.3 months (0.6-23.6), median PFS was 3.5 months (95%CI: 2.4-3.8) and median OS 7.9 months (95%CI: 5.1-10.2). PFS was significantly longer in patients with grade ≥ 2 cutaneous toxicities vs patients with grade 0-1 toxicities (HR = 0.55, 95%CI: 0.33-0.92, P = .020). Expression of EGFR and HER2 was correlated with PFS and OS in multivariate analysis; HER2 expression was correlated with the tumor response. Main severe toxicities were neutropenia (32%), cutaneous rash (37%) and thrombosis/embolisms (35.5%). This triplet combination is effective in terms of disease control, PFS and OS, and acceptable for safety. A larger study to investigate this combination compared to the standard regimen should be discussed.

CDK4/6 Inhibitors in Breast Cancer Treatment: Potential Interactions with Drug, Gene, and Pathophysiological Conditions

Palbociclib, ribociclib, and abemaciclib belong to the third generation of cyclin-dependent kinases inhibitors (CDKis), an established therapeutic class for advanced and metastatic breast cancer. Interindividual variability in the therapeutic response of CDKis has been reported and some individuals may experience increased and unexpected toxicity. This narrative review aims at identifying the factors potentially concurring at this variability for driving the most appropriate and tailored use of CDKis in the clinic. Specifically, concomitant medications, pharmacogenetic profile, and pathophysiological conditions could influence absorption, distribution, metabolism, and elimination pharmacokinetics. A personalized therapeutic approach taking into consideration all factors potentially contributing to an altered pharmacokinetic/pharmacodynamic profile could better drive safe and effective clinical use.

Polymorphisms of Drug-Metabolizing Enzymes and Transporters Contribute to the Individual Variations of Erlotinib Steady State Trough Concentration, Treatment Outcomes, and Adverse Reactions in Epidermal Growth Factor Receptor-Mutated Non-Small Cell Lung Cancer Patients

Background

Erlotinib is presently the first line treatment for non-small cell lung cancer (NSCLC) with epidermal growth factor receptor (EGFR) active mutation. An increasing number of evidences show that the treatment efficacy and toxicities are considerably heterogeneous among individuals. Hence, it is necessary to find biological predictors for further individualized treatment of erlotinib in NSCLC patients.

Methods

Our present study enrolled 87 cases of NSCLC patients who had been administrated erlotinib with a fixed dose (150 mg/d). Eleven polymorphisms in seven genes of drug-metabolizing enzymes and transporters were genotyped and the steady state trough concentrations were also determined.

Results

There were significant variances in the steady-state erlotinib trough plasma concentrations, ranging from 315.6 ng/ml to 4479.83 ng/ml. Erlotinib steady state trough concentration was remarkably lower in current smoking patients. The steady state trough concentration of GG in rs1048943 of CYP1A1 was significantly higher than that of AA allele carriers. The polymorphism of CYP1A2 was significantly associated with the severity of skin rash, and the development of diarrhea was associated with SNPs in ABCB1 and CYP3A5. We also observed that GG allele in CYP1A1 was accompanied with a longer PFS in our study.

Conclusion

A large variability of erlotinib steady state trough concentration was found among Chinese Han population. SNPs in CYP1A1 appeared to influence the steady state trough concentration of erlotinib. Correlation between CYP1A2 polymorphisms and severity of skin rash was observed, together with the correlation between the development of diarrhea and SNPs in ABCB1 and CYP3A5.

The influence of ABCG2 polymorphism on erlotinib efflux in the K562 cell line

Single nucleotide polymorphisms (SNPs) in the gene for multidrug resistance protein ABCG2, an erlotinib transporter, is a possible contributor to the interindividual variation observed in erlotinib pharmacokinetics and toxicity. Therefore, the aim was to study erlotinib efflux by ABCG2 wild-type (wt) and ABCG2 polymorphic variants in the K562 cell line. The chronic myeloid leukemia K562 cell line, neither expressing EGFR nor ABCG2, was transduced with vectors containing the ABCG2 wt, the SNPs: 34 G > A and 421 C > A, or with empty vector (K562/ve). ABCG2-expressing cells were enriched using magnetic sorting and the expression was verified using flow cytometry. Intracellular erlotinib concentrations were analyzed by LC-MS/MS after incubation with 1 µmol/L erlotinib for 60 minutes. All recombinant cell lines were confirmed carriers of the vector and expressed ABCG2. Differences in intracellular erlotinib concentrations were observed between K562/ve and K562 ABCG2 wt and between K562/ve and K562 ABCG2 34G > A (both P ≤ .001, one-way ANOVA with Tukey HSD post hoc test), indicating that the cell lines carrying ABCG2 wt and ABCG2 34G > A actively transports erlotinib out of the cells. The ABCG2 34G > A cell line had a higher transport capacity compared with ABCG2 wt after adjusting for ABCG2 expression (P = .024, t test). No differences were observed between K562/ve and K562 ABCG2 421 C > A. Genetic polymorphism in the ABCG2 gene has an influence on the transport of erlotinib which can contribute to the observed variation in erlotinib pharmacokinetics and toxicity.

Multiple Growth Factor Targeting by Engineered Insulin-like Growth Factor Binding Protein-3 Augments EGF Receptor Tyrosine Kinase Inhibitor Efficacy

Resistance to cancer therapy is a challenge because of innate tumor heterogeneity and constant tumor evolution. Since the pathway of resistance cannot be predicted, combination therapies may address this progression. We discovered that in addition to IGF1 and IGF2, IGFBP-3 binds bFGF, HGF, neuregulin, and PDGF AB with nanomolar affinity. Because growth factors drive resistance, simultaneous inhibition of multiple growth factor pathways may improve the efficacy of precision therapy. Growth factor sequestration by IGFBP-3-Fc enhances the activity of EGFR inhibitors by decreasing cell survival and inhibiting bFGF, HGF, and IGF1 growth factor rescue and also potentiates the activity of other cancer drugs. Inhibition of tumor growth in vivo with adjuvant IGFBP-3-Fc with erlotinib versus erlotinib after treatment cessation supports that the combination reduces cell survival. Inhibition of multiple growth factor pathways may postpone resistance and extend progression-free survival in many cancer indications.

Pharmacogenomic phase transition from personalized medicine to patient-centric customized delivery

Personalized medicine has been a booming area in clinical research for the past decade, in which the detailed information about the patient genotype and clinical conditions were collected and considered to optimize the therapy to prevent adverse reactions. However, the utility of commercially available personalized medicine has not yet been maximized due to the lack of a structured protocol for implementation. In this narrative review, we explain the role of pharmacogenetics in personalized medicine, next-generation personalized medicine, i.e., patient-centric personalized medicine, in which the patient's comfort is considered along with pharmacogenomics to be a primary factor. We extensively discuss the classifications, strategies, tools, and drug delivery systems that can support the implementation of patient-centric personalized medicine from an industrial perspective.

The analysis of pharmacokinetic and pharmacogenomic impact on gefitinib efficacy in advanced non-small cell lung cancer patients: results from a prospective cohort study

Background

The current study is aimed to examine the impact of pharmacokinetics and gene polymorphisms of enzymes involving in absorption, distribution, metabolism and excretion (ADME) on the efficacy of gefitinib in non-small cell lung cancer (NSCLC) patients.

Methods

Eligible patients with indication of gefitinib treatment were prospectively enrolled in this study. Two peripheral blood samples at baseline and before cycle 2 day 1 were collected for the detection of single nucleotide polymorphisms (SNPs) of drug ADME enzymes and trough drug concentration (C_trough) at steady state. Thirteen SNPs were genotyped using the Sequenom Massarray system. C_trough was determined by validated high-performance liquid chromatographic method with tandem mass spectrometric (LC-MS/MS).

Results

Fifty-eight NSCLC patients were enrolled in this study. The median of C_trough was 175ng/mL (range from 47.8 to 470 ng/mL). The trough concentration was not associated with either objective response or progression free survival (PFS). C_trough was significantly lower in CYP3A4 rs2242480 CC + CT genotype than in TT genotype (P=0.019) and in ABCG2 rs2231142 AA genotype than in AC + CC genotype (P=0.031). ABCB1 rs2032582 dominant model was significantly correlated with overall response rate (ORR) and patients with GG phenotype respond better than patients with GT + TT phenotypes (84.6% vs. 51.2%, P=0.032). ABCB1 rs10256836 recessive model was significantly correlated with PFS and patients with GG phenotype achieved longer PFS than patients with GC + CC phenotypes (17.40 vs. 10.33 months, P=0.040).

Conclusions

The C_trough of gefitinib was significantly different between CYP3A4 and ABCG2 genotypes, but not with the efficacy of gefitinib treatment. ABCB1 rs2032582 and rs10256836 polymorphisms were correlated treatment outcome. Polymorphisms analysis of ABCB1 could be a predictive biomarker for gefitinib treatment.

Differential Gene Expression in Erlotinib-Treated Fibroblasts

BACKGROUND

Therapies targeting the epidermal growth factor receptor (EGFR) result in a painful rash, the most common and debilitating toxicity among patients with non-small cell lung cancer (NSCLC) who take EGFR tyrosine kinase inhibitor (TKI) therapy; however, predicting the development and the severity of the rash is difficult.

OBJECTIVE

The aim of this study was to examine how erlotinib-an EGFR TKI that NSCLC patients take to stop or slow tumor growth-altered the transcriptome of dermal fibroblasts.

METHODS

Dermal fibroblasts (ATCC PCS-201-012) were seeded in cell culture flasks, grown under standard conditions, and transferred to cell culture dishes. Cells were treated once daily for 3 days with erlotinib 100 nM (n = 5), erlotinib 1 μM (n = 5), vehicle 1 μM (dimethyl sulfoxide) (n = 5), or no treatment (n = 5). Total RNA was extracted using a standard TRIzol method and hybridized using Affymetrix GeneChip Human Genome U133 Plus 2.0 arrays. Raw intensities generated from the arrays were normalized using a Robust Multiarray Average method and analyzed using analysis of variance in Limma R software. Differentially expressed genes were analyzed using Ingenuity Pathway Analysis to identify canonical or noncanonical signaling pathways enriched in this dataset.

RESULTS

We selected genes for investigation based on their potential role in wound healing (AQP3), rash development (CCL2), fibroblast activation (PALLD), cancer and cancer progression (GDF-15, SLC7A11, MMP12, and DIRAS3), and cell cycle control (CDC6). We were able to validate four of these genes by both Western blot analysis and quantitative polymerase chain reaction (MMP12, CCL2, CDC6, and SLC7A11).

DISCUSSION

If found predictive of rash in future studies using patient samples, our findings may help to identify those at risk for severe rash so that (a) the dose of EGFR TKI therapy may be adjusted; (b) additional treatments for the rash can be developed; and/or (c) precise, patient-centered interventions can be developed so that patients with cancer can better self-manage their rash and adhere to EGFR TKI treatment.

Randomized phase 3 open label study of quality of life of patients on Pemetrexed versus Erlotinib as maintenance therapy for advanced non squamous non EGFR mutated non small cell lung cancer

Background: We planned to compare pemetrexed maintenance with erlotinib maintenance in non squamous non Epidermal Growth Factor Receptor (EGFR) mutated non small cell lung cancer (NSCLC). The null hypothesis for this study was that there would be no difference in quality of life (QOL) between pemetrexed and erlotinib maintenance. Results: The QL2 scores at 3 months were 63.35 (SD 24.99) in pemetrexed arm and 63.01(SD 23.04) in erlotinib arm (p-0.793). Except in 1 domain, the scores were statistically similar between the 2 arms. In the domain of diarrhea, the score was higher as expected in the erlotinib arm (p-0.048). The median progression free survival was 4.5 months (95%CI 4.1-4.9 months) in pemetrexed arm versus 4.5 months (95%CI 3.8-5.2 months) in erlotinib arm (p-0.94). The median overall survival was 16.6 months (15.2-17.9 months) in pemetrexed arm versus 18.3 months (95% CI 13.75-22.91 months) in erlotinib arm (p-0.49). Methods: The study was an open label, single centre, parallel, phase 3 randomized study with 1:1 randomization between maintenance pemetrexed arm and erlotinib arm. Adult patients (age > or = 18 years), with non squamous EGFR mutation, treated with first line palliative therapy, with non progressive disease post 4-6 cycles of pemetrexed-carboplatin were randomized. Primary outcome was change in the score of QOL (Global health status {QL2}) at 3 months. We estimated that with 200 patients, the study had 80% power to detect a significant difference between the two groups in the change in the global health status score at 3 months with an alpha error of 5%, with an effect size of 0.3 SD. Conclusions: Maintenance pemetrexed post pemetrexed-platinum chemotherapy fails to improve QOL or time to event outcomes over maintenance erlotinib in EGFR mutation negative NSCLC.

Pharmacokinetics and safety of erlotinib and its metabolite OSI-420 in infants and children with primary brain tumors

PURPOSE

Erlotinib (Tarceva®), a potent small molecule inhibitor of the epidermal growth factor receptor tyrosine kinase, has been evaluated to treat infants and children with primary brain tumors. The pharmacokinetics of erlotinib and its primary metabolite OSI-420 were characterized and exposure-safety associations were investigated.

METHODS

This analysis involved patients enrolled in two clinical studies and receiving oral erlotinib once daily as part of treatment. Single-dose and steady-state erlotinib and OSI-420 plasma concentrations were assayed using HPLC-MS/MS methods. Population pharmacokinetic modeling and univariate covariate analysis evaluating demographic, clinical and selected CYP3A5, CYP3A4, ABCB1, and ABCG2 genotypes were performed. Associations between erlotinib and OSI-420 pharmacokinetics, and with toxicities (diarrhea and skin rash) occurring post-dose were explored.

RESULTS

Data from 47 patients (0.7-19 years old) were collected and best fitted by one-compartment linear models. Erlotinib and OSI-420 apparent clearances (CL/F and CLm/Fm) were higher in patients < 5 years compared to older patients (mean CL/F: 6.8 vs 3.6 L/h/m2, and mean CLm/Fm: 79 vs 38 L/h/m2, p < 0.001), and were 1.62-fold and 1.73-fold higher in males compared to females (p < 0.01). Moreover, CL/F was 1.53-fold higher in wild-type patients than in patients heterozygous or homozygous mutant for ABCG2 rs55930652 (p < 0.05). Most of the toxicities reported were grade 1. No associations were found between drug pharmacokinetics and drug-induced toxicities.

CONCLUSIONS

Erlotinib therapy was well tolerated by pediatric patients with primary brain tumors. No dosing adjustments based on age or patient characteristics are recommended for this patient population.

Effects of Comedication and Genetic Factors on the Population Pharmacokinetics of Lamotrigine: A Prospective Analysis in Chinese Patients With Epilepsy

Lamotrigine (LTG) is a second-generation anti-epileptic drug widely used for focal and generalized seizures in adults and children, and as a first-line medication in pregnant women and women of childbearing age. However, LTG pharmacokinetics shows high inter-individual variability, thus potentially leading to therapeutic failure or side effects in patients. This prospective study aimed to establish a population pharmacokinetics model for LTG in Chinese patients with epilepsy and to investigate the effects of genetic variants in uridine diphosphate glucuronosyltransferase (UGT) 1A4, UGT2B7, MDR1, ABCG2, ABCC2, and SLC22A1, as well as non-genetic factors, on LTG pharmacokinetics. The study population consisted of 89 patients with epilepsy, with 419 concentrations of LTG. A nonlinear mixed effects model was implemented in NONMEM software. A one-compartment model with first-order input and first-order elimination was found to adequately characterize LTG concentration. The population estimates of the apparent volume of distribution (V/F) and apparent clearance (CL/F) were 12.7 L and 1.12 L/h, respectively. The use of valproic acid decreased CL/F by 38.5%, whereas the co-administration of rifampicin caused an increase in CL/F of 64.7%. The CL/F decreased by 52.5% in SLC22A1-1222AA carriers. Patients with the ABCG2-34AA genotype had a 42.0% decrease in V/F, whereas patients with the MDR1-2677TT and C3435TT genotypes had a 136% increase in V/F. No obvious genetic effect of UGT enzymes was found relative to the concentrations of LTG in Chinese patients. Recommended dose regimens for patients with different gene polymorphisms and comedications were estimated on the basis of Monte Carlo simulations and the established model. These findings should be valuable for developing individualized dosage regimens in adult and adolescent Chinese patients 13–65 years of age.

Impact of Q141K on the Transport of Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitors by ABCG2

The ATP-binding cassette transporter ABCG2 is expressed in various organs, such as the small intestine, liver, and kidney, and influences the pharmacokinetics of drugs that are its substrates. ABCG2 is also expressed by cancer cells and mediates resistance to anticancer agents by promoting the efflux of these drugs. In the present study, we investigated the interactions between epidermal growth factor receptor tyrosine kinase inhibitors and ABCG2 by MTT assay, intracellular drug accumulation assay, and FACS. This study showed that four epidermal growth factor receptor tyrosine kinase inhibitors (EGFR TKIs) (gefitinib, erlotinib, lapatinib, and afatinib) were transported from tumor cells as substrates of ABCG2. Q141K is a common single-nucleotide polymorphism of ABCG2 in Asians. We demonstrated that the extracellular efflux of gefitinib, erlotinib, and lapatinib was reduced by Q141K, whereas afatinib transport was not affected. In addition, all four EGFR TKIs inhibited the transport of other substrates by both wild-type and variant ABCG2 at 0.1 μM concentrations. Accordingly, epidermal growth factor receptor tyrosine kinase inhibitors may induce interactions with other drugs that are substrates of ABCG2, and single-nucleotide polymorphisms of ABCG2 may influence both the pharmacokinetics and efficacy of these anticancer agents.

A safety, pharmacokinetic, pharmacogenomic and population pharmacokinetic analysis of the third-generation EGFR TKI, olmutinib (HM61713), after single oral administration in healthy volunteers

The main objective of this phase I trial was to investigate pharmacokinetics (PKs) of olmutinib in three racial subjects. We also evaluate safety/tolerability and a population PK and pharmacogenomic analysis were performed for explorative purposes. A dose escalation study was conducted in 56 Korean, Japanese and Caucasian subjects. The food effect was assessed in the 300 mg Korean group. Individual PK parameters were calculated by non-compartmental methods and presented by dose and race. Genotype analysis was performed using DMET^® plus to identify genotypes which affect PK characteristics. A population PK model was developed to explore inter-individual variability and to evaluate the influence of possible covariates using NONMEM^® . T_max was 2-3 hour, regardless of race. The mean terminal half-life ranged from 4.8 to 7.4 hour, with no significant differences between dose or racial groups. Dose-normalized C_max and AUC_last were not significantly different between race groups. PK parameters were similar between the fasting and fed conditions. A single-nucleotide polymorphism in the GSTM3 gene (rs4783) and a copy number variation in the GSTM1 gene were significantly related to AUC. A one-compartment model with first-order absorption adequately described the observed olmutinib data. Thirty adverse events were observed in 15 subjects, of which 26 events, all mild, were possibly related to olmutinib. A single oral dose of olmutinib 100-300 mg was safe and well tolerated. PK parameters were dose-proportional and did not differ by race. Food intake did not affect olmutinib absorption. Pharmacogenomic analysis indicated that glutathione S-transferase might be involved in olmutinib metabolism.

Impact of single nucleotide polymorphisms on the efficacy and toxicity of EGFR tyrosine kinase inhibitors in advanced non-small cell lung cancer patients

EGFR tyrosine kinase inhibitors (EGFR-TKIs) are the treatment of choice for advanced-stage (IIIB-IV) NSCLC patients with mutations in EGFR. However, EGFR-TKIs clinical outcomes vary from person to person and these inter-individual differences may be due to genetic factors such as single nucleotide polymorphisms (SNPs). SNPs in genes involved in EGFR-TKIs pharmacodynamics, metabolism and mechanism of action have been demonstrated to be associated with response, survival and toxicity in advanced NSCLC patients treated with EGFR-TKIs. Here we review the influence of gene polymorphisms in the EGFR pathway on clinical outcome and toxicity to EGFR-TKIs in advanced NSCLC patients. The EGFR-216 polymorphism has reported a strong association between response and/or survival to EGFR-TKIs in Caucasian population. Similarly, the effect of EGFR-CA repeats polymorphisms on survival of advanced NSCLC patients treated with EGFR-TKIs have been confirmed both in Caucasian and Asian population. The influence on toxicity of the -216, -191, CA repeats, Arg497Lys and Asp994Asp polymorphisms in EGFR have also been confirmed. Polymorphisms in AKT (rs1130214 and rs1130233) and SMAD3 (rs6494633, rs11071938 and rs11632964) have been associated with survival in advanced NSCLC patients treated with EGFR-TKIs. However, data come from a limited number of studies and need to be confirmed. Finally, polymorphisms in genes coding proteins of the membrane transporters and cytochrome P450 enzymes have been less extensively investigated. There are few studies with small samples, which complicated the generalization of their role in EGFR-TKIs treatment.

Polymorphisms of the Multidrug Pump ABCG2: A Systematic Review of Their Effect on Protein Expression, Function, and Drug Pharmacokinetics

The widespread expression and polyspecificity of the multidrug ABCG2 efflux transporter make it an important determinant of the pharmacokinetics of a variety of substrate drugs. Null ABCG2 expression has been linked to the Junior blood group. Polymorphisms affecting the expression or function of ABCG2 may have clinically important roles in drug disposition and efficacy. The most well-studied single nucleotide polymorphism (SNP), Q141K (421C>A), is shown to decrease ABCG2 expression and activity, resulting in increased total drug exposure and decreased resistance to various substrates. The effect of Q141K can be rationalized by inspection of the ABCG2 structure, and the effects of this SNP on protein processing may make it a target for pharmacological intervention. The V12M SNP (34G>A) appears to improve outcomes in cancer patients treated with tyrosine kinase inhibitors, but the reasons for this are yet to be established, and this residue's role in the mechanism of the protein is unexplored by current biochemical and structural approaches. Research into the less-common polymorphisms is confined to in vitro studies, with several polymorphisms shown to decrease resistance to anticancer agents such as SN-38 and mitoxantrone. In this review, we present a systematic analysis of the effects of ABCG2 polymorphisms on ABCG2 function and drug pharmacokinetics. Where possible, we use recent structural advances to present a molecular interpretation of the effects of SNPs and indicate where we need further in vitro experiments to fully resolve how SNPs impact ABCG2 function.

Epidermal Growth Factor Receptor Gene in Non-Small-Cell Lung Cancer: The Importance of Promoter Polymorphism Investigation

Recently, epidermal growth factor receptor (EGFR) was a key molecule in investigation of lung cancer, and it was a target for a new therapeutic strategy, based on molecular analyses. In this review, we have summarized some issues considering the role of EGFR in lung cancer, its coding gene, and its promoter gene polymorphisms (SNPs) -216G/T and -191C/A in non-small-cell lung cancer (NSCLC). The position of the SNPs indicates their significant role in EGFR regulation. The accumulation of knowledge regarding SNPs lately suggests their significant and important role in the onset of carcinogenesis, the prediction of the onset of metastases, the response to therapy with TKI inhibitors, and the onset of toxic effects of the applied therapy. Based on this, we suggest further studies of the relationship of clinical significance to SNPs in patients with lung tumors.

Population Pharmacokinetics and Adverse Events of Erlotinib in Japanese Patients with Non-small-cell Lung Cancer: Impact of Genetic Polymorphisms in Metabolizing Enzymes and Transporters

Determinants of interindividual variability in erlotinib pharmacokinetics (PK) and adverse events remain to be elucidated. This study with 50 Japanese non-small-cell lung cancer patients treated with oral erlotinib at a standard dose of 150 mg aimed to investigate whether genetic polymorphisms affect erlotinib PK and adverse events. Single nucleotide polymorphisms (SNPs) in genes encoding metabolizing enzymes (CYP1A1, CYP1A2, CYP2D6, CYP3A4, CYP3A5, UGT1A1, UGT2B7, GSTM1, and GSTT1) or efflux transporters (ABCB1, and ABCG2) were analyzed as covariates in a population PK model. The ABCB1 1236C>T (rs1128503) polymorphism, not ABCB1*2 haplotype (1236TT-2677TT-3455TT, rs1128503 TT-rs2032582 TT-rs1045642 TT), was a significant covariate for the apparent clearance (CL/F), with the TT genotype showing a 29.4% decrease in CL/F as compared with the CC and the CT genotypes. A marginally higher incidence of adverse events (mainly skin rash) was observed in the TT genotype group; however, patients with high plasma erlotinib exposure did not always experience skin rash. None of the other SNPs affected PK or adverse events. The ABCB1 genotype is a potential predictor for erlotinib adverse events. Erlotinib might be used with careful monitoring of adverse events in patients with ABCB1 polymorphic variants.

Efficacy of gemcitabine plus erlotinib in rash-positive patients with metastatic pancreatic cancer selected according to eligibility for FOLFIRINOX: A prospective phase II study of the 'Arbeitsgemeinschaft Internistische Onkologie'

INTRODUCTION

In metastatic pancreatic ductal adenocarcinoma (mPDAC) treatment, erlotinib is known to be more effective in patients developing skin rash. Treatment with the FOLFIRINOX regimen is only performed in fit patients following defined inclusion criteria. The present study investigates the efficacy of gemcitabine plus erlotinib (gem/erlotinib) in rash-positive patients fit for FOLFIRINOX.

PATIENTS AND METHODS

For this prospective phase II study, 150 patients were recruited in 20 centres. All patients received gem/erlotinib for 4 weeks (run-in phase); the subsequent treatment was determined by the development of skin rash: patients with rash grades 1-4 continued with gem/erlotinib, rash-negative patients were switched to FOLFIRINOX. Primary study end-point was to achieve a 1-year survival rate in rash-positive patients ≥40%.

RESULTS

Ninety patients were deemed positive for skin rash by the end of the run-in phase, showing a 1-year survival rate of 40.0% (95% confidence interval [CI] 29.8-50.9). Median overall survival (OS) was 10.1 months, progression-free survival (PFS) was 3.8 months and overall response rate (ORR) was 23.3%. Patients switched to FOLFIRINOX (n = 27) had a 1-year survival rate of 48.1% (95% CI 28.7-68.1), a median OS of 10.9 months, a median PFS of 6.6 months and an ORR of 33.3%. Rash-negative patients had a lower quality of life at baseline but seemed to experience an improved control of pain during FOLFIRINOX.

CONCLUSIONS

First-line treatment with gem/erlotinib was effective in fit, rash-positive mPDAC patients achieving a 1-year survival rate comparable to previous reports for FOLFIRINOX. The study was registered at clinicaltrials.gov (NCT0172948) and Eudra-CT (2011-005471-17).

Factors affecting time to reach and recover from gefitinib-induced hepatotoxicity

Gefitinib is an oral tyrosine kinase inhibitor targeting the epidermal growth factor receptor (EGFR) for non-small-cell lung cancer with EGFR mutations. Although a few studies have analyzed the causes of gefitinib-induced hepatotoxicity, research focusing on the time intervals before and after hepatotoxicity has yet to be reported. Therefore, this study investigated two types of factors: the time to reach gefitinib-induced hepatotoxicity and the time for recovery. From January 2013 to December 2014, a retrospective study was carried out on 473 non-small-cell lung cancer patients who were treated with gefitinib. The following data were collected: sex, age, body weight, height, body surface area, underlying disease, Eastern Cooperative Oncology Group Performance Status, smoking history, gefitinib dose, EGFR mutation, and concomitant drugs. Multivariate models showed that patients with mutations in exon 19 had around two-fold higher hepatotoxicity (≥grade 2). Use of CYP3A4 inhibitors and smoking shortened time to hepatotoxicity ∼5-2-fold, respectively, whereas mutations in exon 21 prolonged time to hepatotoxicity by about 2.4-fold. Termination of gefitinib therapy showed 3.8-fold faster recovery. Our study showed that the concomitant use of CYP3A4 inhibitors, smoking, and exon 21 affected the time to reach gefitinib-induced hepatotoxicity. Among the factors examined in this study including hepatotonic use and gefitinib termination, only cessation of gefitinib therapy significantly accelerated recovery.

ABCG2 regulatory single-nucleotide polymorphisms alter in vivo enhancer activity and expression

OBJECTIVES

The expression and activity of the breast cancer resistance protein (ABCG2) contributes toward the pharmacokinetics of endogenous and xenobiotic substrates. The effect of genetic variation on the activity of cis-regulatory elements and nuclear response elements in the ABCG2 locus and their contribution toward ABCG2 expression have not been investigated systematically. In this study, the effect of genetic variation on the in vitro and in vivo enhancer activity of six previously identified liver enhancers in the ABCG2 locus was examined.

METHODS

Reference and variant liver enhancers were tested for their ability to alter luciferase activity in vitro in HepG2 and HEK293T cell lines and in vivo using a hydrodynamic tail vein assay. Positive in vivo single-nucleotide polymorphisms (SNPs) were tested for association with gene expression and for altered protein binding in electrophoretic mobility shift assays.

RESULTS

Multiple SNPs were found to alter enhancer activity in vitro. Four of these variants (rs9999111, rs12508471, ABCG2RE1*2, and rs149713212) decreased and one (rs2725263) increased enhancer activity in vivo. In addition, rs9999111 and rs12508471 were associated with ABCG2 expression in lymphoblastoid cell lines, lymphocytes, and T cells, and showed increased HepG2 nuclear protein binding.

CONCLUSION

This study identifies SNPs within regulatory regions of the ABCG2 locus that alter enhancer activity in vitro and in vivo. Several of these SNPs correlate with tissue-specific ABCG2 expression and alter DNA/protein binding. These SNPs could contribute toward reported tissue-specific variability in ABCG2 expression and may influence the correlation between ABCG2 expression and disease risk or the pharmacokinetics and pharmacodynamics of breast cancer resistance protein substrates.

Associations between ABCG2 gene polymorphisms and gefitinib toxicity in non-small cell lung cancer: a meta-analysis

Background

Gefitinib is frequently used to treat patients with non-small cell lung cancer (NSCLC) and is excreted out from cells via the ATP-binding cassette transporter ABCG2. ABCG2 gene polymorphisms have been suggested to be associated with ABCG2 protein expression and function and may influence the risk of gefitinib toxicity in NSCLC patients. Previous studies on the associations between ABCG2 gene polymorphisms and the toxicity of gefitinib in NSCLC patients have produced conflicting results. The aim of this meta-analysis was to determine whether ABCG2 gene polymorphisms are associated with the risk of gefitinib-induced toxicity in NSCLC patients.

Methods

The PubMed and EMBASE databases were searched systematically for all eligible studies. A relative risk with corresponding 95% CI was calculated to evaluate the associations between ABCG2 gene polymorphisms and gefitinib-induced toxicity.

Results

Data were finally extracted from seven studies and 515 patients were found to meet the inclusion criteria of the meta-analysis. A dominant model showed that there was no significant association between the ABCG2 C421A polymorphism and the risk of gefitinib-induced toxicity, while the ABCG2 G34A polymorphism might be associated with an increased risk of skin toxicity in gefitinib therapy (relative risk =1.54, 95% CI 1.08-2.21, P=0.02). However, more reliable data are required to confirm the associations between the ABCG2 C421A and ABCG2 G34A polymorphisms and the toxicity of gefitinib in NSCLC patients.

Conclusion

While the ABCG2 C421A polymorphism might not be a reliable marker of gefitinib-related toxicity, the ABCG2 G34A genotype may be predictive of the skin toxicity of gefitinib in NSCLC patients. These conclusions need to be verified in further large-scale studies.

DMET™ (Drug Metabolism Enzymes and Transporters): a pharmacogenomic platform for precision medicine

In the era of personalized medicine, high-throughput technologies have allowed the investigation of genetic variations underlying the inter-individual variability in drug pharmacokinetics/pharmacodynamics. Several studies have recently moved from a candidate gene-based pharmacogenetic approach to genome-wide pharmacogenomic analyses to identify biomarkers for selection of patient-tailored therapies. In this aim, the identification of genetic variants affecting the individual drug metabolism is relevant for the definition of more active and less toxic treatments. This review focuses on the potentiality, reliability and limitations of the DMET™ (Drug Metabolism Enzymes and Transporters) Plus as pharmacogenomic drug metabolism multi-gene panel platform for selecting biomarkers in the final aim to optimize drugs use and characterize the individual genetic background.

BCRP/ABCG2 and high-alert medications: Biochemical, pharmacokinetic, pharmacogenetic, and clinical implications

The human breast cancer resistance protein (BCRP/ABCG2) is an ATP-binding cassette efflux transporter that uses ATP hydrolysis to expel xenobiotics from cells, including anti-cancer medications. It is expressed in the gastrointestinal tract, liver, kidney, and brain endothelium. Thus, ABCG2 functions as a tissue barrier to drug transport that strongly influences the pharmacokinetics of substrate medications. Genetic polymorphisms of ABCG2 are closely related to inter-individual variations in therapeutic performance. The common single nucleotide polymorphism c.421C>A, p.Q141K reduces cell surface expression of ABCG2 protein, resulting in lower efflux of substrates. Consequently, a higher plasma concentration of substrate is observed in patients carrying an ABCG2 c.421C>A allele. Detailed pharmacokinetic analyses have revealed that altered intestinal absorption is responsible for the distinct pharmacokinetics of ABCG2 substrates in genetic carriers of the ABCG2 c.421C>A polymorphism. Recent studies have focused on the high-alert medications among ABCG2 substrates (defined as those with high risk of adverse events), such as tyrosine kinase inhibitors (TKIs) and direct oral anti-coagulants (DOACs). For these high-alert medications, inter-individual variation may be closely related to the severity of side effects. In addition, ethnic differences in the frequency of ABCG2 c.421C>A have been reported, with markedly higher frequency in East Asian (∼30-60%) than Caucasian and African-American populations (∼5-10%). Therefore, ABCG2 polymorphisms must be considered not only in the drug development phase, but also in clinical practice. In the present review, we provide an update of basic and clinical knowledge on genetic polymorphisms of ABCG2.

Modelling of atorvastatin pharmacokinetics and the identification of the effect of a BCRP polymorphism in the Japanese population

AIM

Ethnicity plays a modulating role in atorvastatin pharmacokinetics (PK), with Asian patients reported to have higher exposure compared with Caucasians. Therefore, it is difficult to safely extrapolate atorvastatin PK data and models across ethnic groups. This work aims to develop a population PK model for atorvastatin and its pharmacologically active metabolites specifically for the Japanese population. Subsequently, it aimed to identify genetic polymorphisms affecting atorvastatin PK in this population.

METHODS

Atorvastatin acid (ATA) and ortho-hydroxy-atorvastatin acid (o-OH-ATA) plasma concentrations, clinical/demographic characteristics and genotypes for 18 (3, 3, 1, 1, 7, 2 and 1 in the ABCB1, ABCG2, CYP3A4, CYP3A5, SLCO1B1, SLCO2B1 and PPARA genes, respectively) genetic polymorphisms were collected from 27 Japanese individuals (taking 10 mg atorvastatin once daily) and analysed using a population PK modelling approach.

RESULTS

The population PK model developed (one-compartment for ATA linked through metabolite formation to an additional compartment describing the disposition of o-OH-ATA) accurately described the observed data and the associated population variability. Our analysis suggested that patients carrying one variant allele for the rs2622604 polymorphism (ABCG2) show a 55% (95% confidence interval: 16-131%) increase in atorvastatin oral bioavailability relative to the value in individuals without the variant allele.

CONCLUSION

The current work reports the identification in the Japanese population of a BCRP polymorphism, not previously associated with the PK of any statin, that markedly increases ATA and o-OH-ATA exposure. The model developed may be of clinical importance to guide dosing recommendations tailored specifically for the Japanese.

Use of a physiologically based pharmacokinetic model to simulate drug-drug interactions between antineoplastic and antiretroviral drugs

Background

Co-administration of antineoplastics with ART is challenging due to potential drug-drug interactions (DDIs). However, trials specifically assessing such DDIs are lacking. Our objective was to simulate DDIs between the antineoplastics erlotinib and gefitinib with key antiretroviral drugs and to predict dose adjustments using a physiologically based pharmacokinetic (PBPK) model.

Methods

In vitro data describing chemical properties and pharmacokinetic processes of each drug and their effect on cytochrome P450 isoforms were obtained from the literature. Plasma drug-concentration profiles were simulated in a virtual population of 50 individuals receiving erlotinib or gefitinib alone or with darunavir/ritonavir, efavirenz or etravirine. Simulated pharmacokinetic parameters and the magnitude of DDIs with probe drugs (midazolam, maraviroc) were compared with literature values. Erlotinib and gefitinib pharmacokinetics with and without antiretrovirals were compared and dose-adjustment strategies were evaluated.

Results

Simulated parameters of each drug and the magnitude of DDIs with probe drugs were in agreement with reference values. Darunavir/ritonavir increased erlotinib and gefitinib exposure, while efavirenz and etravirine decreased erlotinib and gefitinib concentrations. Based on our predictions, dose-adjustment strategies may consist of once-daily dosing erlotinib at 25 mg and gefitinib at 125 mg with darunavir/ritonavir; or erlotinib at 200 mg and gefitinib at 375 mg with etravirine. The interaction with efavirenz was not overcome even after doubling erlotinib or gefitinib doses.

Conclusions

PBPK models predicted the in vivo pharmacokinetics of erlotinib, gefitinib and the antiretrovirals darunavir/ritonavir, efavirenz and etravirine, and the DDIs between them. The simulated dose-adjustments may represent valuable strategies to optimize antineoplastic therapy in HIV-infected patients.

Biomarker analysis of the phase 3 TORCH trial for first line erlotinib versus chemotherapy in advanced non-small cell lung cancer patients

BACKGROUND

The TORCH phase III trial compared the efficacy of first-line erlotinib followed by chemotherapy at progression (experimental arm) with the reverse sequence (standard arm) in unselected advanced non-small cell lung cancer (NSCLC) patients. Here we report biomarker analyses.

METHODS

EGFR and KRAS mutation, expression of EGFR family members and of cMET and PTEN and EGFR and ABCG2 germline polymorphisms were tested on tumor tissue or blood samples to either confirm previously proposed predictive role or describe it in an explorative setting. Progression-free survival (PFS) was the primary end-point, overall survival, response rate and side effects (diarrhoea and skin toxicity) were secondary end-points. Interactions between biomarkers and treatment were studied with multivariable models (either Cox model or logistic regression). Statistical analyses accounted for multiple comparisons.

RESULTS

At least one biomarker was assessed in 324 out of 760 patients in the TORCH study. EGFR mutation was more common in female (P = 0.0001), East Asians (P < 0.0001) and never smoker (P < 0.0001) patients; low MET protein expression by IHC (H-score <200) was more frequent in squamous (P < 0.00009) and ABCG2 C/A or A/A polymorphism was more frequent among East-Asian patients (P = 0.0003). A significant interaction was found for EGFR mutation in PFS and response rate analyses while no predictive effect on OS was found for any biomarker. No biomarker tested was prognostic for PFS and OS. No polymorphism was significantly associated with skin toxicity or diarrhea.

CONCLUSION

In the present study, beyond the known role of EGFR mutation, no other biomarker has predictive or prognostic role.

Oxidative stress mediates an increased formation of vascular endothelial growth factor in human hepatocarcinoma cells exposed to erlotinib

The tyrosine kinase inhibitor erlotinib targets the receptor of epidermal growth factor (EGFR) involved in development of hepatocellular carcinoma (HCC).

Although inefficient in established HCC, erlotinib has been recently proposed for HCC chemoprevention. Since Cyp3A4 and Cyp1A2 enzymes metabolize erlotinib in the liver, the insights into the mechanisms of erlotinib effects on liver cells with maintained drug metabolizing activity are needed.

We applied erlotinib to both commercially available (SNU398, Huh7) and established in Austria HCC cell lines (HCC-1.2, HCC-3). Cyp3A4 and Cyp1A2, microarray gene expression, cell viability, LDH release, DHFC fluorescence were assessed. VEGF expression was analysed by real-time RT-PCR and ELISA.

Higher cumulative expression of erlotinib metabolizing enzymes was observed in HCC-1.2 and HCC-3 cells. Gene expression microarray analysis showed upregulation of VEGF signalling by erlotinib. VEGF was increased up to 134 ± 14% (n = 5, p = 0.002) in HCC-1.2, HCC-3 and Huh7 cells. Interventions by Cyp1A2 and Mek2siRNA, MEK inhibitor UO126, diphenylene iodonium, as well as a combination of N-acetylcysteine with selenium all inhibited VEGF upregulation caused by erlotinib.

Thus, erlotinib increases VEGF production by mechanisms involving Cyp1A2, oxidative stress and MEK1/2. VEGF may favour angiogenesis and growth of early HCC tumours limiting the therapeutic and chemopreventive effects of erlotinib.