ErbB2pY -1248 as a predictive biomarker for Parkinson's disease based on research with RPPA technology and in vivo verification.

AIMS: This study aims to reveal a promising biomarker for Parkinson's disease (PD) based on research with reverse phase protein array (RPPA) technology for the first time and in vivo verification, which gains time for early intervention in PD, thus increasing the effectiveness of treatment and reducing disease morbidity. METHODS AND RESULTS: We employed RPPA technology which can assess both total and post-translationally modified proteins to identify biomarker candidates of PD in a cellular PD model. As a result, the phosphorylation (pY-1248) of the epidermal growth factor receptor (EGFR) ErbB2 is a promising biomarker candidate for PD. In addition, lapatinib, an ErbB2 tyrosine kinase inhibitor, was used to verify this PD biomarker candidate in vivo. We found that lapatinib-attenuated dopaminergic neuron loss and PD-like behavior in the zebrafish PD model. Accordingly, the expression of ErbB2pY-1248 significantly increased in the MPTP-induced mouse PD model. Our results suggest that ErbB2pY-1248 is a predictive biomarker for PD. CONCLUSIONS: In this study, we found that ErbB2pY-1248 is a predictive biomarker of PD by using RPPA technology and in vivo verification. It offers a new perspective on PD diagnosing and treatment, which will be essential in identifying individuals at risk of PD. In addition, this study provides new ideas for digging into biomarkers of other neurodegenerative diseases.

The effect of shikonin on the metabolism of lapatinib in vitro, and in vivo.

PURPOSE: The purpose of this study was to develop an assay for simultaneous determination of lapatinib and its metabolites (N-dealkylated lapatinib and O-dealkylated lapatinib) by ultra-high performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS), and to determine the interaction between shikonin and lapatinib in vitro, in vivo, in silico and its mechanism of action. METHODS: A new UPLC-MS/MS method for the determination of the concentrations of lapatinib and its metabolites was developed. In vivo, Sprague-Dawley (SD) rats were given lapatinib with or without shikonin. In vitro, to study the interaction mechanism, rat liver microsomes (RLMs), human liver microsomes (HLMs) and recombinant human CYP3A4.1 were used for determining enzyme kinetics. Lastly, we used in silico molecular docking to investigate the molecular mechanism of inhibition. RESULTS: The selectivity, precision, accuracy, stability, matrix effect and recovery of UPLC-MS/MS all met the requirements of quantitative analysis of biological samples. Administration of lapatinib combined with shikonin resulted in significantly increased pharmacokinetic parameters (AUC(0-t) and Cmax) of lapatinib, indicating that shikonin increased the exposure of lapatinib in rats. Moreover, in vitro kinetic measurements indicated that shikonin was a time-independent inhibitor, which inhibited the metabolism of lapatinib through a competitive mechanism in RLMs, while noncompetitive inhibition type in both HLMs and CYP3A4.1. Molecular docking analysis further verified the non-competitive inhibition of shikonin on lapatinib in CYP3A4.1. CONCLUSION: We developed an UPLC-MS/MS assay for simultaneous determination of lapatinib and its metabolites. It could be successfully applied to the study of pharmacokinetic interaction of shikonin on the inhibition of lapatinib metabolism in vivo and in vitro. In the end, further studies are needed to determine if such interactions are indeed valid in humans and if the interaction is clinically relevant.

The involvement of hepatic cytochrome P450s in the cytotoxicity of lapatinib.

Lapatinib, an oral tyrosine kinase inhibitor used as a first-line treatment for HER2-positive breast cancer, has been reported to be associated with hepatotoxicity; however, the underlying mechanisms remain unclear. In this study, we report that lapatinib causes cytotoxicity in multiple types of hepatic cells, including primary human hepatocytes, HepaRG cells, and HepG2 cells. A 24-h treatment with lapatinib induced cell cycle disturbances, apoptosis, and DNA damage, and decreased the protein levels of topoisomerase in HepG2 cells. We investigated the role of cytochrome P450 (CYP)-mediated metabolism in lapatinib-induced cytotoxicity using our previously established HepG2 cell lines, which express each of 14 CYPs (1A1, 1A2, 1B1, 2A6, 2B6, 2C8, 2C9, 2C18, 2C19, 2D6, 2E1, 3A4, 3A5, and 3A7). We demonstrate that lapatinib is metabolized by CYP1A1, 3A4, 3A5, and 3A7. Among these, lapatinib-induced cytotoxicity and DNA damage were attenuated in cells overexpressing CYP3A5 or 3A7. Additionally, we measured the production of three primary metabolites of lapatinib (O-dealkylated lapatinib, N-dealkylated lapatinib, and N-hydroxy lapatinib) in CYP1A1-, 3A4-, 3A5-, and 3A7-overexpressing HepG2 cells. We compared the cytotoxicity of lapatinib and its 3 metabolites in primary human hepatocytes, HepaRG cells, and HepG2 cells and demonstrated that N-dealkylated lapatinib is more toxic than the parent drug and the other metabolites. Taken together, our results indicate that lapatinib-induced cytotoxicity involves multiple mechanisms, such as apoptosis and DNA damage; that N-dealkylated lapatinib is a toxic metabolite contributing to the toxic effect of lapatinib; and that CYP3A5- and 3A7-mediated metabolism plays a role in attenuating the cytotoxicity of lapatinib.

ErbBs in Lens Cell Fibrosis and Secondary Cataract.

Purpose: TGFß-induced epithelial-to-myofibroblast transition (EMyT) of lens cells has been linked to the most common vision-disrupting complication of cataract surgery-namely, posterior capsule opacification (PCO; secondary cataract). Although inhibitors of the ErbB family of receptor tyrosine kinases have been shown to block some PCO-associated processes in model systems, our knowledge of ErbB signaling in the lens is very limited. Here, we investigate the expression of ErbBs and their ligands in primary cultures of chick lens epithelial cells (dissociated cell-derived monolayer cultures [DCDMLs]) and how TGFß affects ErbB function. Methods: DCDMLs were analyzed by immunofluorescence microscopy and Western blotting under basal and profibrotic conditions. Results: Small-molecule ErbB kinase blockers, including the human therapeutic lapatinib, selectively inhibit TGFß-induced EMyT of DCDMLs. Lens cells constitutively express ErbB1 (EGFR), ErbB2, and ErbB4 protein on the plasma membrane and release into the medium ErbB-activating ligand. Culturing DCDMLs with TGFß increases soluble bioactive ErbB ligand and markedly alters ErbBs, reducing total and cell surface ErbB2 and ErbB4 while increasing ErbB1 expression and homodimer formation. Similar, TGFß-dependent changes in relative ErbB expression are induced when lens cells are exposed to the profibrotic substrate fibronectin. A single, 1-hour treatment with lapatinib inhibits EMyT in DCDMLs assessed 6 days later. Short-term exposure to lower doses of lapatinib is also capable of eliciting a durable response when combined with suboptimal levels of a mechanistically distinct multikinase inhibitor. Conclusions: Our findings support ErbB1 as a therapeutic target for fibrotic PCO, which could be leveraged to pharmaceutically preserve the vision of millions of patients with cataracts.

Effect of HER2-targeted therapy on PDX and PDX-derived organoids generated from HER2-positive salivary duct carcinoma.

BACKGROUND: We previously established a patient-derived xenograft (PDX) model, patient-derived organoids (PDOs), and PDX-derived organoids (PDXOs) for salivary duct carcinoma (SDC). Using these models, this study examined the therapeutic effect of human epidermal growth factor receptor 2 (HER2) blockade on HER2-positive SDC. METHODS: The therapeutic effect of lapatinib was assessed in SDC PDXOs with regards to cell growth, receptor/downstream signaling molecule expression, phosphorylation levels, and apoptosis. Effect of lapatinib treatment was evaluated in vivo in SDC PDX mice. RESULTS: The siRNA knockdown of HER2 and lapatinib suppressed cell proliferation in SDC PDXOs. Lapatinib inhibited the phosphorylation of HER2 and its downstream targets, and induced apoptosis in SDC PDXOs. Lapatinib also significantly reduced tumor volumes compared with that of the control in SDC PDX mice. CONCLUSION: For the first time, we demonstrated the efficacy of anti-HER2 therapy in HER2-positive SDC using preclinical models of SDC PDX and PDXO.

Macrophages M2 polarization is involved in lapatinib-mediated chemopreventive effects in the lung cancer.

M2 polarized tumor-associated macrophages (TAMs) have a multifunctional role in cancer initiation, progression, metastasis, and contribute to chemotherapeutic resistance. Therefore, identifying M2 polarized TAMs is a potential target for cancer therapeutic intervention. The underlying mechanism that target the TAMs M2 polarized macrophages remains primarily uncharacterized; however, only a few compounds have been identified that inhibit TAMs M2 polarized macrophages. In this research, we investigated that lapatinib could effectively suppress the expression of IL_13-induced M2 polarized macrophages surface markers i.e., CD163 and CD206, and downregulation of M2 genes such as Fizz1, Mrc1, Arg1, IL-10, Ym1, nd CCL2 in vitro. Moreover, lapatinib abrogated the M2 polarized macrophage-mediated cancer cells invasion and migration. Mechanistically, in our study, lapatinib inhibited IL-13 triggered STAT6 phosphorylation. Furthermore, in LLCs tumor model, lapatinib significantly reduced tumorigenesis, followed by the downregulation of percentages of M2 marker CD206+ and CD68+ in the tumor. This downregulation correlates with chemopreventive effect of lapatinib. All taken together, these results demonstrated that lapatinib effectively prevents the macrophage M2 polarization and indicates a potential mechanism for preventing the tumor growth via M2 polarized polarization intervention.

PTX3 from vascular endothelial cells contributes to trastuzumab-induced cardiac complications.

AIMS: Trastuzumab, the first humanized monoclonal antibody that targets human epidermal growth factor receptor 2 (ERBB2/HER2), is currently used as a first-line treatment for HER2 (+) tumours. However, trastuzumab increases the risk of cardiac complications without affecting myocardial structure, suggesting a distinct mechanism of cardiotoxicity. METHODS AND RESULTS: We used medium from trastuzumab-treated human umbilical vein endothelial cells (HUVECs) to treat CCC-HEH-2 cells, the human embryonic cardiac tissue-derived cell lines, and human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) to assess the crosstalk between vascular endothelial cells (VECs) and cardiomyocytes. Protein mass spectrometry analysis was used to identify the key factors from VECs that regulate the function of cardiomyocytes. We applied RNA-sequencing to clarify the mechanism, by which PTX3 causes cardiac dysfunction. We used an anti-human/rat HER2 (neu) monoclonal antibody to generate a rat model that was used to evaluate the effects of trastuzumab on cardiac structure and function and the rescue effects of lapatinib on trastuzumab-induced cardiac side effects. Medium from trastuzumab-treated HUVECs apparently impaired the contractility of CCC-HEH-2 cells and iPSC-CMs. PTX3 from VECs caused defective cardiomyocyte contractility and cardiac dysfunction in mice, phenocopying trastuzumab treatment. PTX3 affected calcium homoeostasis in cardiomyocytes, which led to defective contractile properties. EGFR/STAT3 signalling in VECs contributed to the increased expression and release of PTX3. Notably, lapatinib, a dual inhibitor of EGFR/HER2, could rescue the cardiac complications caused by trastuzumab by blocking the release of PTX3. CONCLUSION: We identified a distinct mode of cardiotoxicity, wherein the activation of EGFR/STAT3 signalling by trastuzumab in VECs promotes PTX3 excretion, which contributes to the impaired contractility of cardiomyocytes by inhibiting cellular calcium signalling. We confirmed that lapatinib could be a feasible preventive agent against trastuzumab-induced cardiac complications and provided the rationale for the combined application of lapatinib and trastuzumab in cancer therapy.

EGFR blocker lapatinib inhibits the synthesis of matrix metalloproteinases from synovial fibroblasts.

BACKGROUND: Epidermal growth factor receptor (EGFR) family members and their associated ligands may be related to bone and joint destruction in rheumatoid arthritis. Matrix metalloproteinases are responsible for joint and bone tissue degradation. This study is intended to investigate the effect of epidermal growth factor receptor inhibition by lapatinib on the synthesis of matrix metalloproteinases in in vitro. METHODS: Synovial fibroblast cell culture was obtained from a patient with rheumatoid arthritis who underwent knee arthroplasty. Interleukin-1ß (IL-1ß) and tumor necrosis factor-α (TNF-α) were added to the cell culture to stimulate synovial fibroblast cells and create an inflammatory character. Understimulated and nonstimulated conditions, lapatinib was applied to the culture in four different concentrations of 25, 50, 100, and 200 µmol. Then, matrix metalloproteinase -1, -3, and, -13 levels were assessed. RESULTS: When stimulated with IL-1ß and TNF-α, the synthesis of matrix metalloproteinases from synovial fibroblast was increased significantly. When lapatinib is added to the stimulated synovial fibroblasts, matrix metalloproteinases synthesis is significantly suppressed. DISCUSSION: Inhibition of the EGFR pathway with lapatinib suppresses matrix metalloproteinases synthesis. Our results suggest EGFR pathway inhibition may be a promising option to prevent joint destruction in the treatment of rheumatoid arthritis.

Dual targeting micelles loaded with paclitaxel and lapatinib for combinational therapy of brain metastases from breast cancer.

Due to the presence of the blood-brain barrier (BBB), the delivery of general drugs into the brain tissue remains to be a tricky problem. For patients with brain metastases from breast cancer, drug delivery systems must overcome this physical barrier. Targeted nano vehicles arise as a promising alternative to deliver drugs to brain tissues successively. Herein, a dual targeting micelle drug delivery system loaded with paclitaxel (PTX) and lapatinib (LPTN) was developed for combinational therapy of brain metastases. In our study, it was shown the micelles modified with Angiopep-2 had high loading efficiency of paclitaxel and lapatinib (Ang-MIC-PTX/LP). In addition, Ang-MIC-PTX/LP could transport across the in vitro BBB model and accumulate in breast cancer cells. After intravenous injection, Ang-MIC significantly accumulated in the brain metastasis. Ang-MIC-PTX/LP could also extend the life span of brain metastasis mouse models. Overall, this study provided a promising method for treatment of brain metastases from breast cancer.

In vitro assessment of the photo(geno)toxicity associated with Lapatinib, a Tyrosine Kinase inhibitor.

The epidermal growth factor receptors EGFR and HER2 are the main targets for tyrosine kinase inhibitors (TKIs). The quinazoline derivative lapatinib (LAP) is used since 2007 as dual TKI in the treatment of metastatic breast cancer and currently, it is used as an oral anticancer drug for the treatment of solid tumors such as breast and lung cancer. Although hepatotoxicity is its main side effect, it makes sense to investigate the ability of LAP to induce photosensitivity reactions bearing in mind that BRAF (serine/threonine-protein kinase B-Raf) inhibitors display a considerable phototoxic potential and that afloqualone, a quinazoline-marketed drug, causes photodermatosis. Metabolic bioactivation of LAP by CYP3A4 and CYP3A5 leads to chemically reactive N-dealkylated (N-LAP) and O-dealkylated (O-LAP) derivatives. In this context, the aim of the present work is to explore whether LAP and its N- and O-dealkylated metabolites can induce photosensitivity disorders by evaluating their photo(geno)toxicity through in vitro studies, including cell viability as well as photosensitized protein and DNA damage. As a matter of fact, our work has demonstrated that not only LAP, but also its metabolite N-LAP have a clear photosensitizing potential. They are both phototoxic and photogenotoxic to cells, as revealed by the 3T3 NRU assay and the comet assay, respectively. By contrast, the O-LAP does not display relevant photobiological properties. Remarkably, the parent drug LAP shows the highest activity in membrane phototoxicity and protein oxidation, whereas N-LAP is associated with the highest photogenotoxicity, through oxidation of purine bases, as revealed by detection of 8-Oxo-dG.

Detoxication versus Bioactivation Pathways of Lapatinib In Vitro: UGT1A1 Catalyzes the Hepatic Glucuronidation of Debenzylated Lapatinib.

O-Dealkylation of the tyrosine kinase inhibitor lapatinib by cytochrome P450 3A enzymes is implicated in the development of lapatinib-induced hepatotoxicity. Conjugative metabolism of debenzylated lapatinib (M1) via glucuronidation and sulfation is thought to be a major detoxication pathway for lapatinib in preclinical species (rat and dog), limiting formation of the quinoneimine reactive metabolite. Glucuronidation of M1 by human recombinant UDP-glucuronosyltransferases (UGTs) has been reported in vitro; however, the relative UGT enzyme contributions are unknown, and the interspecies differences in the conjugation versus bioactivation pathways of M1 have not been fully elucidated. In the present study, reaction phenotyping experiments using human recombinant UGT enzymes and enzyme-selective chemical inhibitors demonstrated that UGT1A1 was the major hepatic UGT enzyme involved in lapatinib M1 glucuronidation. Formation of the M1-glucuronide by human liver microsomes from UGT1A1-genotyped donors was significantly correlated with UGT1A1 activity as measured by 17ß-estradiol 3-glucuronidation (R 2 = 0.90). Interspecies differences were found in the biotransformation of M1 in human, rat, and dog liver microsomal and 9000g supernatant (S9) fractions via glucuronidation, sulfation, aldehyde oxidase-mediated oxidation, and bioactivation to the quinoneimine trapped as a glutathione (GSH) conjugate. Moreover, we demonstrated the sequential metabolism of lapatinib in primary human hepatocytes to the M1-glucuronide, M1-sulfate, and quinoneimine-GSH conjugate. M1 glucuronidation was highly correlated with the rates of M1 formation, suggesting that O-dealkylation may be the rate-limiting step in lapatinib biotransformation. Interindividual variability in the formation and clearance pathways of lapatinib M1 likely influences the hepatic exposure to reactive metabolites and may affect the risk for hepatotoxicity. SIGNIFICANCE STATEMENT: We used an integrated approach to examine the interindividual and interspecies differences in detoxication versus bioactivation pathways of lapatinib, which is associated with idiosyncratic hepatotoxicity. In addition to cytochrome P450 (P450)-mediated bioactivation, we report that multiple non-P450 pathways are involved in the biotransformation of the primary phenolic metabolite of lapatinib in vitro, including glucuronidation, sulfation, and aldehyde oxidase mediated oxidation. UGT1A1 was identified as the major hepatic enzyme involved in debenzylated lapatinib glucuronidation, which may limit hepatic exposure to the potentially toxic quinoneimine.

First-in-human, phase I single-ascending-dose study of the safety, pharmacokinetics, and relative bioavailability of selatinib, a dual EGFR-ErbB2 inhibitor in healthy subjects.

We assessed the pharmacokinetics and safety of a single oral administration of selatinib to healthy Chinese subjects and evaluated the potential bioavailability advantage of selatinib relative to lapatinib. Healthy subjects aged 18-40 years were enrolled in this two-part study: Part 1, a single ascending dose (50-500 mg), randomized, double-blind, placebo-control study with 64 subjects; and Part 2, an open-label, positive control, randomized, three-treatment, three-period, three-sequence crossover design study, with 6 subjects administered a single 500-mg dose of selatinib tablets (A), selatinib suspension (B), or lapatinib tablets C) per cycle. In part 1, selatinib was well-tolerated up to the planned maximum dose of 500 mg; thus the maximum tolerated dose was not attained. Twenty-two adverse events were observed in 19 (36.5%) of the 52 subjects administered the test drug. The most common drug-related adverse event was diarrhea. The mean selatinib peak plasma concentration was 69.4-494 ng/mL, which was achieved in a median peak time of 3.5-4.5 h, with a mean elimination half-life between 13.8 and 15.8 h. In Part 2, A and B showed similar bioavailability. Plasma exposure to the active drug (selatinib plus the metabolite, lapatinib) after A intake was more than two-fold higher than that of the same dose of C. In the dose range of 50-500 mg, selatinib was safe and well-tolerated by healthy Chinese subjects, and it conformed with linear pharmacokinetics. Active exposure to selatinib was much greater than that to lapatinib, supporting its development as an adjuvant for anticancer treatment.

Metabolic Stability Assessment of New PARP Inhibitor Talazoparib Using Validated LC-MS/MS Methodology: In silico Metabolic Vulnerability and Toxicity Studies.

BACKGROUND: Talazoparib (BMN673) is a new poly(ADP-ribose) polymerase inhibitor that has been FDA approved for patients suffering from metastatic breast cancer with germline BRCA mutations. METHOD AND RESULTS: In the current study, an accurate and efficient liquid chromatography-tandem mass spectrometry (LC-MS/MS) analytical methodology was developed for TZB estimation in addition to its metabolic stability assessment. TZB and lapatinib (LAP) (which is chosen as an internal standard; IS) were separated using reversed phase elution system (Hypersil C18 column) with an isocratic mobile phase. The linearity range of the established method was 5-500 ng/mL (r2 ≥ 0.999) in the human liver microsomes (HLMs) matrix. Different parameters were calculated to confirm the method sensitivity (limit of quantification was 2.0 ng/mL), and reproducibility (intra- and inter-day precision and accuracy were below 3.1%) of our methodology. For evaluation of TZB metabolic stability in HLM matrix, intrinsic clearance (9.59 µL/min/mg) and in vitro half-life (72.7 mins) were calculated. TZB treatment discontinuations were reported due to adverse events and dose accumulation, so in silico metabolic vulnerability (experimental and in silico) and toxicity assessment (in silico) of TZB were performed utilizing P450 Metabolism and DEREK modules of StarDrop software. CONCLUSION: TZB is slowly metabolized by the liver. TZB was reported to be minimally metabolized by the liver that approved our outcomes. We do recommend that plasma levels be monitored in cases when talazoparib is used for a long period of time, since it is possible for TZB to bioaccumulate after multiple doses to toxic levels. According to our knowledge, the current method is considered the first LC-MS/MS methodology for evaluating TZB metabolic stability. Further drug discovery studies can be done depending on this concept allowing the designing of new series of compounds with more safety profile through reducing side effects and improving metabolic behavior.

Botryllamide G is an ABCG2 inhibitor that improves lapatinib delivery in mouse brain.

Introduction: Transporters comprising the blood-brain barrier complicate delivery of many therapeutics to the central nervous system. The present study ascertained whether the natural product botryllamide G is viable for in vivo inhibition of ABCG2 using lapatinib as a probe for ABCB1 and ABCG2-mediated efflux from the brain. Methods: Wild-type and Mdr1a/Mdr1b (-/-) mice were treated with botryllamide G and lapatinib ("doublet therapy"), and while a separate cohort of wild-type mice was treated with botryllamide, tariquidar and lapatinib ("triplet therapy"). Results: Botryllamide G demonstrates biphasic elimination with a rapid distribution, decreasing below the in vitro IC50 of 6.9 µM within minutes, yet with a relatively slower terminal half-life (4.6 h). In Mdr1a/Mdr1b (-/-) mice, doublet therapy resulted in a significant increase in brain lapatinib AUC at 8 h (2058 h*ng/mL vs 4007 h*ng/mL; P = .031), but not plasma exposure (P = .15). No significant differences were observed after 24 h. Lapatinib brain exposure was greater through 1 h when wild-type mice were administered triplet therapy (298 h*pg/mg vs 120 h*pg/mg; P < .001), but the triplet decreased brain AUC through 24 h vs. mice administered lapatinib alone (2878 h*pg/mg vs 4461hr*ng/mL; P < .001) and did not alter the brain:plasma ratio. Conclusions: In summary, the ABCG2 inhibitor, botryllamide G, increases brain exposure to lapatinib in mice lacking Abcb1, although the combination of botryllamide G and tariquidar increases brain exposure in wild-type mice only briefly (1 h). Additional research is needed to find analogs of this compound that have better pharmacokinetics and pharmacodynamic effects on ABCG2 inhibition.

Theoretical study on the mechanism of N- and α-carbon oxidation of lapatinib catalyzed by cytochrome P450 monooxygenase.

Lapatinib, an orally active dual tyrosine kinase inhibitor, is efficacious in combination therapy with capecitabine for advanced metastatic breast cancer. Despite its importance, it has been associated with hepatotoxicity observed in clinical trials and postmarketing surveillance. The mechanisms of hepatotoxicity at the chemical and cellular levels may link to drug metabolism. In this study, the N- and α-carbon oxidation processes of lapatinib catalyzed by CYP3A4 were explored by density functional theory method. The calculation results show that oxidation of C6 is the primary metabolic process and carboxylic acid is the main metabolic product. Both hydroxylation of C8 and subsequent formation of primary amines are feasible. However, it is not easy for the primary amines to form active metabolites nitroso, which indicates that there are other paths for the production of nitroso. Carboxylic acid is not the main metabolite of N7 oxidation because of higher hydrolysis energy barrier of intermediate nitrone. It is worthy to study subsequent N-hydroxylation and its downstream reaction, which may be the main pathway for the formation of nitroso. These results lay the foundation for drug design and optimization.

Validated LC-MS/MS assay for quantification of the newly approved tyrosine kinase inhibitor, dacomitinib, and application to investigating its metabolic stability.

Dacomitinib (DMB) is a second-generation irreversible tyrosine kinase inhibitor (TKI) that is claimed to overcome the disadvantages of the resistance reported for first-line epidermal growth factor receptor (EGFR) TKIs. Towards the end of 2018, the US Food and Drug Administration approved DMB in the form of VIZIMPRO tablets. In the current study, a validated LC-MS/MS assay was established for DMB quantification in rat liver microsomes (RLMs) with application to the drug metabolic stability assessment. Chromatographic resolution of DMB and lapatinib (internal standard) was achieved using an isocratic mobile phase and a reversed-phase C18 column. The linearity of the established LC-MS/MS assay ranged from 2 to 500 ng/mL with r2 ≥ 0.9999. The limit of detection (LOD) and limit of quantification (LOQ) were 0.35 and 1.1 ng/mL, respectively. The precision and accuracy (both intra-day and inter-day) were 0.84-3.58% and 92.2-100.32%, respectively. The metabolic stability of DMB in the RLM matrix was estimated by calculating two parameters, in vitro t1/2 (0.97 mL/min/kg) and intrinsic clearance (157.5 min). Such values infer that DMB would be excreted very slowly from the human body, which might lead to possible bioaccumulation. To the best of our knowledge, this is the first method for DMB analysis in RLMs with metabolic stability estimation.

Monitoring activities of receptor tyrosine kinases using a universal adapter in genetically encoded split TEV assays.

Receptor tyrosine kinases (RTKs) play key roles in various aspects of cell biology, including cell-to-cell communication, proliferation and differentiation, survival, and tissue homeostasis, and have been implicated in various diseases including cancer and neurodevelopmental disorders. Ligand-activated RTKs recruit adapter proteins through a phosphotyrosine (p-Tyr) motif that is present on the RTK and a p-Tyr-binding domain, like the Src homology 2 (SH2) domain found in adapter proteins. Notably, numerous combinations of RTK/adapter combinations exist, making it challenging to compare receptor activities in standardised assays. In cell-based assays, a regulated adapter recruitment can be investigated using genetically encoded protein-protein interaction detection methods, such as the split TEV biosensor assay. Here, we applied the split TEV technique to robustly monitor the dynamic recruitment of both naturally occurring full-length adapters and artificial adapters, which are formed of clustered SH2 domains. The applicability of this approach was tested for RTKs from various subfamilies including the epidermal growth factor (ERBB) family, the insulin receptor (INSR) family, and the hepatocyte growth factor receptor (HGFR) family. Best signal-to-noise ratios of ligand-activated RTK receptor activation was obtained when clustered SH2 domains derived from GRB2 were used as adapters. The sensitivity and robustness of the RTK recruitment assays were validated in dose-dependent inhibition assays using the ERBB family-selective antagonists lapatinib and WZ4002. The RTK split TEV recruitment assays also qualify for high-throughput screening approaches, suggesting that the artificial adapter may be used as universal adapter in cell-based profiling assays within pharmacological intervention studies.

Lapatinib, a Dual Inhibitor of Epidermal Growth Factor Receptor (EGFR) and HER-2, Enhances Radiosensitivity in Mouse Bladder Tumor Line-2 (MBT-2) Cells In Vitro and In Vivo.

BACKGROUND The aim of this study was to evaluate the effect of lapatinib, a dual inhibitor of epidermal growth factor receptor (EGFR) and HER-2, on the radiosensitivity of murine bladder tumor line-2 (MBT-2) cells in vitro and in vivo. MATERIAL AND METHODS MBT-2 cells were pretreated with lapatinib at doses ranging from 200-1,000 nM for 30 min followed by radiation at doses ranging from 2.5-10 Gy for 30 min. A clonogenic assay (colony formation assay) assessed cell survival. Western blot measured phosphorylated epidermal growth factor receptor (p-EGFR), phosphorylated AKT (p-AKT), and phosphorylated HER-2 (p-HER2) and the apoptosis marker, PARP. The C3H/HeN mouse tumor xenograft model underwent subcutaneous injection of MBT-2 cells; mice were divided into four groups, treated with lapatinib (200 mg/kg), radiation (15 Gy), a combination of both, and with vehicle (control). RESULTS Lapatinib pretreatment, combined with radiation, decreased MBT-2 cell survival, and suppressed radiation-activated levels of p-EGFR and p-HER-2. MBT-2 cells treated with a 10 Gy dose of radiation and 1000 nM of lapatinib showed combination index (CI) values of <1 indicating synergy. Increased expression of γ-H2AX, indicated increased apoptosis. In mice with tumor xenografts, a daily dose of lapatinib (200 mg/kg/day) for seven days combined with radiation on the fourth day suppressed tumor growth to a greater degree than radiation alone. CONCLUSIONS Lapatinib treatment enhanced the radiation sensitivity in an in vitro and in vivo murine bladder cancer model by decreasing radiation-mediated EGFR and HER-2 activation, and by causing DNA damage leading to cell apoptosis.