EGFR (IC50 = 10.2 nM); ErbB2 (IC50 = 9.8 nM); ErbB4 (IC50 = 367 nM)

In BT474 and HN5 cells, lapatinib (GW2016; 0.03-10 µM; 6 hours) tosylate treatment suppresses the dose-dependent autophosphorylation of the EGFR and ErbB-2 receptors. AKT serine 473 phosphorylation is inhibited by GW2016 in a dose-dependent manner [1]. Human tumor cell line growth is specifically inhibited by lapatinib (GW2016; 72 hours; HN5, A-43, BT474, N87, and CaLu-3 cells) tosylate therapy [1]. G1 arrest is brought on by lapatinib (GW2016; 1–10 µM; 72 hours; HN5 cells) therapy [1].

Lapatinib (GW2016; 30-100 mg/kg; oral; twice daily; for 21 days; CD-1 nude female mice) tosylate therapy in a dose-response manner at 30 and 100 mg/kg The growth of tumor xenografts of HN5 cells was decreased by kg, and tumor growth was totally stopped at higher doses [1]. Lapatinib (~100 mg/kg) given orally twice a day significantly and dose-dependently inhibits the growth of HN5 and BT474 xenografts.[1]

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The combination of lapatinib with radiation therapy suppressed the growth of MBT-2 xenograft tumors in mice [2]
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. The outcomes of lapatinib treatment of tumor xenografts in this animal model showed that a daily dose of lapatinib (oral, 200 mg/kg/day) for seven days, combined with radiation on the fourth day caused a significant suppression in the growth of xenografts tumors compared with irradiation alone (Figure 6A). However, oral lapatinib treatment alone had minimal effect. The results suggested that an oral dose of lapatinib increased the radiation-mediated suppression of xenografts tumors by about 60%. The results of immunohistochemistry for expression of HER-2 and EGFR in tumors recovered from mice at the end of treatment protocol of seven days showed the involvement of radiation in enhancing the levels of EGFR and HER-2 (Figure 6B). However, lapatinib, in combination with radiation therapy, suppressed the radiation-mediated activation of EGFR and HER-2 in xenograft tumors. The outcomes of this in vivo experiment indicated that lapatinib induced radiosensitization by inhibiting the radiation-mediated expression of EGFR and HER-2, in addition to facilitating DNA damage. [2]

The process of measuring the inhibition of phosphorylation of a peptide substrate yields the IC50 values for inhibition of enzyme activity. The EGFR and ErbB2 intracellular kinase domains are isolated using a baculovirus expression system. In round-bottomed polystyrene 96-well plates, EGFR and ErbB2 reactions are carried out with a final volume of 45 μL. The reaction mixtures consist of the following components: 50 μM Peptide A [Biotin-(amino hexonoic acid)-EEEEYFELVAKKK-CONH2], 1 mM dithiothreitol, 2 mM MnCl2, 10 μM ATP, 1 μCi of [γ33P] ATP/reaction, and 1 μL of DMSO containing serial dilutions of Lapatinib starting at 10 μM. The indicated purified type-1 receptor intracellular domain is added to start the reaction. One pmol of added enzyme is used for each reaction (20 nM). After 10 minutes at 23°C, 45 μL of 0.5% phosphoric acid in water is added to stop the reaction. The 75 μL of the finished reaction mix is put onto phosphocellulose filter plates. The plates undergo three rounds of filtering and washing with 200 μL of 0.5% phosphoric acid. Each well receives 50 μL of the scintillation cocktail, and the assay is measured using a Packard Topcount. 10-point dose-response curves are used to calculate IC50 values.

Cell proliferation assay[1]
Cell Types: HN5, A-43, BT474, N87 and CaLu-3 Cell
Tested Concentrations: 1 nM-100 µM
Incubation Duration: 72 hrs (hours)
Experimental Results: Inhibition of growth of tumor cells overexpressing EGFR or ErbB-2 .

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Cell cycle analysis[1]
Cell Types: HN5 Cell
Tested Concentrations: 1 µM or 10 µM
Incubation Duration: 72 hrs (hours)
Experimental Results: Induction of G1 arrest.

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Western Blot Analysis[1]
Cell Types: BT474 and HN5 Cell
Tested Concentrations: 0.03 µM, 0.1 µM, 0.3 µM, 1 µM, 3 µM or 10 µM
Incubation Duration: 6 hrs (hours)
Experimental Results: Inhibition of receptor autophosphorylation of EGFR and ErbB-2 dose-response approach. Phosphorylation of AKT serine 473 was also inhibited in a dose-dependent manner.

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For 72 hours, cells are exposed to different lapatinib concentrations. Methylene blue staining is used to estimate the relative number of cells. A Spectra microplate reader is used to measure the absorbance at 620 nm. Propidium iodide staining, antibody detection of incorporated BrdUrd, and propidium iodide staining are used to analyze cell death and the cell cycle.

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Clonogenic assay (colony formation assay) [2]
To test the effects of lapatinib and irradiation on colony formation, cells were seeded using six-well plates and a cell density of 1×105 cells/well. The cells were exposed to different radiation doses, but received pretreatment with lapatinib (200–1,000 nM) for 30 min, with the control cells treated with dimethyl sulfoxide (DMSO). After pre-treatment with lapatinib, and following irradiation, the cells were cultured for a further week. Counting of the cell colonies was done using a light microscope (×100 magnification), and the colonies were defined as a group of 50 cells or more.

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Cell cycle analysis [2]
The cell cycle distribution was done by flow cytometry analysis. Propidium iodide (PI) staining for DNA in cells was analyzed. For the protocol, 106 cells/ml were exposed to lapatinib and irradiation as previously described and were collected after centrifugation. The cells were stained with PI (15 μg/ml) in PBS with 5 μg/ml DNase-free RNase and Tween-20 (0.5%). The samples were analyzed using an Attune™ NxT Acoustic Focusing Cytometer.

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Immunofluorescence microscopic studies [2]
The MBT-2 cells were transferred onto coverslips pre-coated with poly-lysine for 12 h to allow the cells to attach to the surface. The cells were exposed to a radiation dose of 2.5 Gy either alone, or in combination with 100 nM of lapatinib . The cells were then incubated for 45 min and were then washed three times with ice-cold PBS, then treated for 30 min with a 4% solution of formaldehyde in PBS for fixation, followed by incubation in 0.5% Triton X-100/PBS for 60 min, 5% bovine serum albumin (BSA) for 60 min, and a final incubation for 2 h with fluorescein isothiocyanate (FITC)-conjugated anti-phospho-Histone γ-H2AX antibody (1: 1500). The cells were washed with PBS and mounted in Vectashield mounting medium containing diamidino-2-phenylindole. A Zeiss LSM 8 microscope was used to examine the γ-H2AX nuclei at high power, and a mean of at least 120 nuclei was counted. The mean of the γ-H2AX foci/nuclei indicated the number of DNA double-strand breaks.

Animal/Disease Models: CD-1 female nude mice (4-6 weeks old) HN5 cells [1]
Doses: 30 mg/kg, 100 mg/kg
Route of Administration: oral; twice (two times) daily; for 21 days
Experimental Results: Inhibition of tumor xenograft growth of HN5 cells in a dose-response manner.

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The C3H/HEN mice were inoculated with a subcutaneous injection of a suspension of MBT-2 cells (100 μl) (1×107 cells/100 μl) into the right flank of the mice on day 1. After one week, the tumor size was measured using vernier calipers, and the volume was calculated. A mean volume of 162 mm3 was regarded as a criterion for tumor establishment. After successful establishment of tumor, the mice were divided into four groups: Group 1, the control group (vehicle treated with 0.5% methylcellulose and 0.1% Tween-80); Group 2, lapatinib -treated (200 mg/kg/day); Group 3, vehicle and irradiation (15 Gy) on day 4; Group 4, lapatinib -treated (200 mg/kg/day) and irradiated (15 Gy) on the 4th day. The body weight of all the mice was recorded every week. Positron emission tomography (PET) and computed tomography (CT) scans were taken (PET/CT) by intravenous injection of the animals with 14 MBq (378 Ci) of fludeoxyglucose (FDG) in saline via the tail vein. [2]

Absorption, Distribution and Excretion
Absorption following oral administration of lapatinib is incomplete and variable.
Lapatinib undergoes extensive metabolism, primarily by CYP3A4 and CYP3A5, with minor contributions from CYP2C19 and CYP2C8 to a variety of oxidated metabolites, none of which accounts for more than 14% of the dose recovered in the feces or 10% of lapatinib concentration in plasma.
After administration of a single oral dose of (14)C-lapatinib, the predominant route of elimination of drug-related material in the mouse, rat and dog was in the feces, with very little urinary excretion. Most of the dose was eliminated within 48 hours post-dose.
Elimination of lapatinib is predominantly through metabolism by CYP3A4/5 with negligible (<2%) renal excretion. Recovery of parent lapatinib in feces accounts for a median of 27% (range 3% to 67%) of an oral dose.
Systemic exposure to lapatinib is increased when administered with food. Lapatinib AUC values were approximately 3- and 4-fold higher (Cmax approximately 2.5- and 3-fold higher) when administered with a low-fat (5% fat-500 calories) or with a high-fat (50% fat-1,000 calories) meal, respectively.
Lapatinib is highly bound (>99%) to albumin and alpha-1 acid glycoprotein. In vitro studies indicate that lapatinib is a substrate for the transporters breast cancer-resistance protein (BCRP, ABCG2) and P-glycoprotein (P-gp, ABCB1). Lapatinib has also been shown to inhibit P-gp, BCRP, and the hepatic uptake transporter OATP 1B1, in vitro at clinically relevant concentrations.
For more Absorption, Distribution and Excretion (Complete) data for Lapatinib (7 total), please visit the HSDB record page.

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Metabolism / Metabolites
Lapatinib undergoes extensive metabolism, primarily by CYP3A4 and CYP3A5, with minor contributions from CYP2C19 and CYP2C8 to a variety of oxidated metabolites, none of which accounts for more than 14% of the dose recovered in the feces or 10% of lapatinib concentration in plasma.
Lapatinib, an oral breast cancer drug, has recently been reported to be a mechanism-based inactivator of cytochrome P450 (P450) 3A4 and also an idiosyncratic hepatotoxicant. It was suggested that formation of a reactive quinoneimine metabolite was involved in mechanism-based inactivation (MBI) and/or hepatotoxicity. We investigated the mechanism of MBI of P450 3A4 by lapatinib. Liquid chromatography-mass spectrometry analysis of P450 3A4 after incubation with lapatinib did not show any peak corresponding to irreversible modifications. The enzymatic activity inactivated by lapatinib was completely restored by the addition of potassium ferricyanide. These results indicate that the mechanism of MBI by lapatinib is quasi-irreversible and mediated via metabolic intermediate complex (MI complex) formation. This finding was verified by the increase in a signature Soret absorbance at approximately 455 nm. Two amine oxidation products of the metabolism of lapatinib by P450 3A4 were characterized: N-hydroxy lapatinib (M3) and the oxime form of N-dealkylated lapatinib (M2), suggesting that a nitroso or another related intermediate generated from M3 is involved in MI complex formation. In contrast, P450 3A5 was much less susceptible to MBI by lapatinib via MI complex formation than P450 3A4. In addition, P450 3A5 had a significantly lower ability than 3A4 to generate M3, consistent with N-hydroxylation as the initial step in the pathway to MI complex formation. In conclusion, our results demonstrate that the primary mechanism for MBI of P450 3A4 by lapatinib is not irreversible modification by the quinoneimine metabolite, but quasi-irreversible MI complex formation mediated via oxidation of the secondary amine group of lapatinib.
Lapatinib undergoes extensive metabolism in humans to numerous oxidated and N- and O-dealkylated products. In vitro studies using human hepatocytes and microsomes indicated that lapatinib is primarily metabolised by CYP3A4 and CYP3A5, with smaller contributions from CYP2C8. Additional studies indicated that CYP1A2, 2D6, 2C9 and 2C19 may also be involved, but to a lesser extent. The most prominent metabolites are the carboxylic acid GW42393 and the O-dealkylated phenol GW690006. N-oxidation of the secondary aliphatic amine produced a cascade of about 8 minor metabolites. Relative to parent drug, GW690006 produced approximately equipotent inhibition of ErbB1-dependent tumour cell growth in vitro, but was approximately 100-fold less potent in ErbB2- dependent tumour cells. GW342393 was found to be approximately 40-fold less potent than parent drug in both ErbB1- and ErbB2-dependent tumour cells. They are unlikely to contribute to the biological activity of lapatinib.
Lapatinib, an oral tyrosine kinase inhibitor used for breast cancer, has been reported to cause idiosyncratic hepatotoxicity. Recently, it has been found that lapatinib forms a metabolite-inhibitor complex (MIC) with CYP3A4 via the formation of an alkylnitroso intermediate. Because CYP3A5 is highly polymorphic compared with CYP3A4 and also oxidizes lapatinib, we investigated the interactions of lapatinib with CYP3A5. Lapatinib inactivated CYP3A5 in a time-, concentration-, and NADPH-dependent manner using testosterone as a probe substrate with K(I) and k(inact) values of 0.0376 mM and 0.0226 min(-1), respectively. However, similar results were not obtained when midazolam was used as the probe substrate, suggesting that inactivation of CYP3A5 by lapatinib is site-specific. Poor recovery of CYP3A5 activity postdialysis and the lack of a Soret peak confirmed that lapatinib does not form a MIC with CYP3A5. The reduced CO difference spectrum further suggested that a large fraction of the reactive metabolite of lapatinib is covalently adducted to the apoprotein of CYP3A5. GSH trapping of a reactive metabolite of lapatinib formed by CYP3A5 confirmed the formation of a quinoneimine-GSH adduct derived from the O-dealkylated metabolite of lapatinib. In silico docking studies supported the preferential formation of an O-dealkylated metabolite of lapatinib by CYP3A5 compared with an N-hydroxylation reaction that is predominantly catalyzed by CYP3A4. In conclusion, lapatinib appears to be a mechanism-based inactivator of CYP3A5 via adduction of a quinoneimine metabolite.
Metabolism of lapatinib was assessed both quantitatively and qualitatively in the plasma and excreta of rats (10 mg/kg), dogs (10 mg/kg), mice (30 mg/kg) and humans (250 mg) following a single oral administration of (14)C-lapatinib. In general, (14)C-lapatinib was primarily metabolized, secreted in the bile and eliminated in the feces. In the nonclinical and clinical metabolism studies, urine samples were not analyzed due to the low percentage of the dose excreted by this route. In plasma, (14)C-lapatinib represented the largest single component in all species. Lapatinib was more extensively metabolised in male rats than in female rats, however the metabolic profiles were similar. In dogs and humans, 14C-lapatinib was the only quantifiable peak present. In humans, lapatinib accounted for only approximately half of the radioactivity in the plasma. The remaining radioactivity was attributed to at least 8 metabolites detected by LC-MS but below the limit of radiochemical quantification (approximately 5% of the total radioactivity in pooled plasma). These metabolites were attributed to the N-oxidation cascade that was also observed in vitro as well as in rats and mice. In both mice and rats, only a few of these metabolites were quantifiable in plasma by radiochemical detection, but all were characterized by mass spectrometry. Thus, no unique circulating metabolites were observed in humans

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Biological Half-Life
Single-dose terminal half life: 14.2 hours Effective multiple-dose half life: 24 hours
At clinical doses, the terminal phase half-life following a single dose was 14.2 hours; accumulation with repeated dosing indicates an effective half-life of 24 hours.
In a mass-balance study, single 250 mg doses of (14)C-labelled lapatinib administered to 6 healthy volunteers produced serum concentrations of radio-labelled material representing parent drug and metabolites that peaked 4 hr after the dose and declined with a median half-life of 6 hr. Plasma concentrations of lapatinib declined with a half-life of 14 hours.

Toxicity Summary
IDENTIFICATION AND USE: Lapatinib is a yellow solid formulated into film-coated tablets. Lapatinib, an inhibitor of human epidermal growth factor receptor type 2 (HER2/ERBB2) and epidermal growth factor receptor (HER1/EGFR/ERBB1) tyrosine kinases, is an antineoplastic agent. It is used in combination with capecitabine for the treatment of patients with advanced or metastatic breast cancer whose tumors overexpress HER2 and who have received prior therapy including an anthracycline, a taxane, and trastuzumab. It is also used in combination with letrozole for the treatment of postmenopausal women with hormone receptor-positive metastatic breast cancer that overexpresses the HER2 receptor, and for whom hormonal therapy is indicated. HUMAN EXPOSURE AND TOXICITY: Asymptomatic and symptomatic cases of overdose have been reported. The doses ranged from 2,500 to 9,000 mg daily, the duration varied between 1 and 17 days. Symptoms observed include lapatinib-associated events and in some cases sore scalp, sinus tachycardia (with otherwise normal ECG), and/or mucosal inflammation. At therapeutic doses, hepatotoxicity, manifested as increases in serum concentrations of aminotransferases and bilirubin, has been observed in clinical trials and post-marketing experience with lapatnib. The hepatotoxicity may be severe and deaths have been reported. Causality of the deaths is uncertain. The hepatotoxicity may occur within days to several months after initiation of treatment. Women should avoid the use of lapatinib during pregnancy. While there are not adequate and well-controlled studies in pregnant women, lapatinib has been associated with adverse reproductive effects in animals. If used during pregnancy, the patient should be apprised of the potential fetal hazard. ANIMAL STUDIES: While there was no evidence of carcinogenicity in a two year mouse study, increased mortality which was related to skin toxicities was observed in males at 150 and 300 mg/kg/day and in females at 300 mg/kg/day. In a two-year rat carcinogenicity study, increased mortality was observed in males at 500 mg/kg/day and females at 300 mg/kg/day, and was related to skin toxicities. Renal infarcts and papillary necrosis were observed in females from 60 mg/kg/day and 180 mg/kg/day, respectively. An increased incidence of benign hemangioma of the mesenteric lymph nodes was noted in males from 120 mg/kg/day and in females at 180 mg/kg/day but was within background range. The clinical significance of these findings to humans is not known. Lapatinib did not affect male or female rat gonadal function, mating, or fertility at doses up to 120 mg/kg/day in females and up to 180 mg/kg/day in males. Studies in pregnant rats and rabbits revealed no teratogenic effects. However, in rats, minor anomalies (left-sided umbilical artery, cervical rib and precocious ossification) occurred at the maternally toxic dose of 120 mg/kg/day. In rabbits, lapatinib was associated with maternal toxicity at 60 and 120 mg/kg/day and abortions at 120 mg/kg/day. At maternally toxic doses, decreased fetal body weights, decreased number of live fetuses and minor skeletal variations were noted. Lapatinib was not clastogenic or mutagenic in a battery of assays including the Chinese hamster chromosome aberration assay, the Ames assay, human lymphocyte chromosome aberration assay and an in vivo rat bone marrow chromosome aberration assay.

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Hepatotoxicity
Elevations in serum aminotransferase levels are common during lapatinib therapy, occurring in up to half of patients. Values greater than 5 times the upper limit of normal (ULN) occur in 2% to 6% of patients but are usually transient and asymptomatic. Dose adjustments or temporary discontinuations are rarely required for liver test abnormalities.
Since its introduction into clinical use, lapatinib has been linked to several cases of clinically apparent acute liver injury. The clinical features of injury have not been well defined, but the onset is usually within 1 to 3 months of starting lapatinib and the pattern of serum enzyme elevations is typically hepatocellular or mixed (Case 1). Sufficent numbers of reports of liver injury have been made to the Food and Drug Administration such that lapatinib is listed as having hepatotoxicity that can be fatal. The frequency of serious liver injury is estimated to be 0.2%, but is likely higher. Immunoallergic and autoimmune features are uncommon, although genetic studies suggest that lapatinib hepatotoxicity is linked to specific HLA alleles. Most instances are self-limited, but several cases of acute liver failure have been reported with tyrosine kinase receptor inhibitors including imatinib, sunitinib, lapatinib, gefitinib and erlotinib. Recurrence of injury is common with reexposure but may not occur upon switching to another kinase receptor inhibitor.
Likelihood score: B (likely cause of clinically apparent acute liver injury).

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Effects During Pregnancy and Lactation
◉ Summary of Use during Lactation
No information is available on the clinical use of lapatinib during breastfeeding. Because lapatinib is more than 99% bound to plasma proteins, the amount in milk is likely to be low. However, its half-life is about 24 hours and it might accumulate in the infant. It is also given in combination with capecitabine, which may increase the risk to the infant. The manufacturer recommends that breastfeeding be discontinued during lapatinib therapy and for 1 week after the last dose.
◉ Effects in Breastfed Infants
Relevant published information was not found as of the revision date.
◉ Effects on Lactation and Breastmilk
Relevant published information was not found as of the revision date.

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Protein Binding
Highly bound (>99%) to albumin and alpha-1 acid glycoprotein

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Interactions
Grapefruit products should be avoided because of the potential for increased plasma lapatinib concentrations.
In patients receiving lapatinib and paclitaxel (a CYP2C8 and P-gp substrate) concomitantly, systemic exposure (AUC over 24 hours) of paclitaxel was increased by 23%. However, the manufacturer states that because of limitations of the study design, these data may underestimate the potential increase in paclitaxel exposure during concomitant use.
Concomitant administration of lapatinib and oral digoxin (a P-gp substrate) increased systemic exposure (AUC) of digoxin by approximately 2.8-fold. In patients receiving digoxin, serum digoxin concentrations should be measured prior to initiation of lapatinib therapy and monitored throughout concomitant therapy. If serum digoxin concentrations exceed 1.2 ng/mL, digoxin dosage should be reduced by 50%.
Because lapatinib may cause prolongation of the QT interval, lapatinib should be used with caution in patients receiving concomitant therapy with other drugs (e.g., antiarrhythmic agents) known to prolong the QT interval.
For more Interactions (Complete) data for Lapatinib (10 total), please visit the HSDB record page.

[1]. The effects of the novel, reversible epidermal growth factor receptor/ErbB-2 tyrosine kinase inhibitor, GW2016, on the growth of human normal and tumor-derived cell lines in vitro and in vivo. Mol Cancer Ther. 2001 Dec;1(2):85-94.

[2]. 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. Med Sci Monit. 2018 Aug 20;24:5811–5819.

A quinazoline derivative that inhibits EPIDERMAL GROWTH FACTOR RECEPTOR and HER2 (RECEPTOR, ERBB-2) tyrosine kinases. It is used for the treatment of advanced or metastatic breast cancer, where tumors overexpress HER2.
See also: Lapatinib Ditosylate (annotation moved to).

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Drug Indication
Tyverb is indicated for the treatment of patients with breast cancer , whose tumours overexpress HER2 (ErbB2): in combination with capecitabine for patients with advanced or metastatic disease with progression following prior therapy, which must have included anthracyclines and taxanes and therapy with trastuzumab in the metastatic setting; in combination with trastuzumab for patients with hormone-receptor-negative metastatic disease that has progressed on prior trastuzumab therapy or therapies in combination with chemotherapy; in combination with an aromatase inhibitor for post-menopausal women with hormone-receptor-positive metastatic disease, not currently intended for chemotherapy. The patients in the registration study had not previously been treated with trastuzumab or an aromatase inhibitor. No data are available on the efficacy of this combination relative to trastuzumab in combination with an aromatase inhibitor in this patient population.

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Therapeutic Uses
Antineoplastic Agents; Protein Kinase Inhibitors
Tykerb is indicated in combination with capecitabine for the treatment of patients with advanced or metastatic breast cancer whose tumors overexpress HER2 and who have received prior therapy including an anthracycline, a taxane, and trastuzumab. Limitation of Use: Patients should have disease progression on trastuzumab prior to initiation of treatment with Tykerb in combination with capecitabine. /Included in US product label/
Tykerb is indicated in combination with letrozole for the treatment of postmenopausal women with hormone receptor-positive metastatic breast cancer that overexpresses the HER2 receptor for whom hormonal therapy is indicated. /Included in US product label/
EXPL THER Although there are effective HER2-targeted agents, novel combination strategies in HER2-overexpressing breast cancers are needed for patients whose tumors develop drug resistance. To develop new therapeutic strategy, ... the combinational effect of entinostat, an oral isoform-selective histone deacetylase type I inhibitor, and lapatinib, a HER2/EGFR dual tyrosine kinase inhibitor, in HER2+ breast cancer cells /was investigated/. ... The combinational synergistic effect and its mechanism by CellTiter Blue assay, flow cytometry, anchorage-independent growth, quantitative real-time PCR, small interfering RNA, Western blotting, and mammary fat pad xenograft mouse models /was assessed/. /It was/ found that compared with entinostat or lapatinib alone, the two drugs in combination synergistically inhibited proliferation (P < 0.001), reduced in vitro colony formation (P < 0.05), and resulted in significant in vivo tumor shrinkage or growth inhibition in two xenograft mouse models (BT474 and SUM190, P < 0.001). The synergistic anti-tumor activity of the entinostat/lapatinib combination was due to downregulation of phosphorylated Akt, which activated transcriptional activity of FOXO3, resulting in induction of Bim1 (a BH3 domain-containing pro-apoptotic protein). Furthermore, entinostat sensitized trastuzumab/lapatinib-resistance-HER2-overexpressing cells to the trastuzumab/lapatinib combination and enhanced the anti-proliferation effect compare with single or double combination treatment. This study provides evidence that entinostat has enhanced anti-tumor effect in combination with HER2-targeted reagent, lapatinib, and resulting in induction of apoptosis by FOXO3-mediated Bim1 expression. ... Findings justifies for conducting a clinical trial of combinational treatment with entinostat, lapatinib, and trastuzumab in patients with HER2-overexpressing breast cancer resistant to trastuzumab-based treatment.

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Drug Warnings
/BOXED WARNING/ WARNING: HEPATOTOXICITY. Hepatotoxicity has been observed in clinical trials and postmarketing experience. The hepatotoxicity may be severe and deaths have been reported. Causality of the deaths is uncertain.
Hepatotoxicity (ALT or AST >3 times the upper limit of normal and total bilirubin >2 times the upper limit of normal) has been observed in clinical trials (<1% of patients) and postmarketing experience. The hepatotoxicity may be severe and deaths have been reported. Causality of the deaths is uncertain. The hepatotoxicity may occur days to several months after initiation of treatment. Liver function tests (transaminases, bilirubin, and alkaline phosphatase) should be monitored before initiation of treatment, every 4 to 6 weeks during treatment, and as clinically indicated. If changes in liver function are severe, therapy with Tykerb should be discontinued and patients should not be retreated with Tykerb.
Lapatinib may cause fetal harm; fetal anomalies, abortion, and death of offspring within days after birth have been demonstrated in animals. Pregnancy should be avoided during therapy. If lapatinib is used during pregnancy or if the patient becomes pregnant while receiving the drug, the patient should be apprised of the potential hazard to the fetus.
FDA Pregnancy Risk Category: D /POSITIVE EVIDENCE OF RISK. Studies in humans, or investigational or post-marketing data, have demonstrated fetal risk. Nevertheless, potential benefits from the use of the drug may outweigh the potential risk. For example, the drug may be acceptable if needed in a life-threatening situation or serious disease for which safer drugs cannot be used or are ineffective./
For more Drug Warnings (Complete) data for Lapatinib (14 total), please visit the HSDB record page.

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Pharmacodynamics
Lapatinib is a small molecule and a member of the 4-anilinoquinazoline class of kinase inhibitors. An anti-cancer drug, lapatinib was developed by GlaxoSmithKline (GSK) as a treatment for solid tumours such as breast and lung cancer. It was approved by the FDA on March 13, 2007, for use in patients with advanced metastatic breast cancer in conjunction with the chemotherapy drug capecitabine.

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The epidermal growth factor receptor (EGFR) and ErbB-2 transmembrane tyrosine kinases are currently being targeted by various mechanisms in the treatment of cancer. GW2016 is a potent inhibitor of the ErbB-2 and EGFR tyrosine kinase domains with IC50 values against purified EGFR and ErbB-2 of 10.2 and 9.8 nM, respectively. This report describes the efficacy in cell growth assays of GW2016 on human tumor cell lines overexpressing either EGFR or ErbB-2: HN5 (head and neck), A-431 (vulva), BT474 (breast), CaLu-3 (lung), and N87 (gastric). Normal human foreskin fibroblasts, nontumorigenic epithelial cells (HB4a), and nonoverexpressing tumor cells (MCF-7 and T47D) were tested as negative controls. After 3 days of compound exposure, average IC50 values for growth inhibition in the EGFR- and ErbB-2-overexpressing tumor cell lines were < 0.16 microM. The average selectivity for the tumor cells versus the human foreskin fibroblast cell line was 100-fold. Inhibition of EGFR and ErbB-2 receptor autophosphorylation and phosphorylation of the downstream modulator, AKT, was verified by Western blot analysis in the BT474 and HN5 cell lines. As a measure of cytotoxicity versus growth arrest, the HN5 and BT474 cells were assessed in an outgrowth assay after a transient exposure to GW2016. The cells were treated for 3 days in five concentrations of GW2016, and cell growth was monitored for an additional 12 days after removal of the compound. In each of these tumor cell lines, concentrations of GW2016 were reached where outgrowth did not occur. Furthermore, growth arrest and cell death were observed in parallel experiments, as determined by bromodeoxyuridine incorporation and propidium iodide staining. GW2016 treatment inhibited tumor xenograft growth of the HN5 and BT474 cells in a dose-responsive manner at 30 and 100 mg/kg orally, twice daily, with complete inhibition of tumor growth at the higher dose. Together, these results indicate that GW2016 achieves excellent potency on tumor cells with selectivity for tumor versus normal cells and suggest that GW2016 has value as a therapy for patients with tumors overexpressing either EGFR or ErbB-2. [1]

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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/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.

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In the mid-1980s, it was recognized that overexpression of epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor-2 (HER2) adversely affected the prognosis of some cancer patients. Because EGFR and HER2 are key regulators of cell growth, differentiation, and survival, it was believed that inhibition of these receptors would block downstream signaling and would be antiproliferative. Indeed, by the late 1980s, researchers were creating some of the first targeted inhibitors of tyrosine kinase activity. It was in this context that we began our efforts to develop potential disease therapies using a small-molecule approach to selectively target EGFR and HER2.
The challenge for developing small-molecule EGFR/HER2 inhibitors lay in determining the potency and selectivity specific to their kinase domains. Several key components of our study permitted us to drive discovery efforts. First, novel chemistry produced numerous compounds for testing. Second, a broad-based kinase biochemical screening platform allowed us to examine compounds on multiple kinase targets. Third, the creation of a cell-based panel included lines dependent on EGFR or HER2 signaling as well as suitable control cell lines. This cell panel not only provided automated evaluation of molecules for potency and selectivity in the cell's complex environment but also made the investigation of players downstream of EGFR and HER2 possible, linking EGFR and HER2 inhibition to cell-cycle arrest and apoptosis. The last component, in vivo xenograft models, enabled us to continue this research by using pharmacokinetic and pharmacodynamic markers. Our work with a highly committed and motivated team of scientists ultimately resulted in the innovative discovery of GW2016, also known as GW572016, which later became the cancer therapy lapatinib.
The selectivity of lapatinib for HER2 and EGFR kinase domains and its activity in HER2-overexpressing cell lines (e.g., breast and gastric cancer) and EGFR-overexpressing cell lines (e.g., head and neck cancer) provided a foundation to test lapatinib in selected patient populations. The U.S. Food and Drug Administration's approval in 2007 of lapatinib, in combination with capecitabine for treatment of advanced or metastatic HER2-overexpressing breast cancer, provided another option for patients whose disease progressed on trastuzumab (a humanized monoclonal antibody directed against the extracellular domain of HER2). Ongoing clinical trials are examining lapatinib activity in HER2-overexpressing breast cancer, HER2-overexpressing gastric cancer, and head and neck cancer.
Looking ahead, an HER2- and EGFR-targeted strategy will be similar to most future cancer therapies (i.e., in combination with other agents). Recent clinical evidence has shown the synergy of dual blockade with the combination of lapatinib and trastuzumab in patients with HER2-positive metastatic breast cancer. In addition, dual blockade of the HER2-signaling pathway is also being examined in the neoadjuvant and adjuvant settings. Other clinical studies are evaluating HER2 and EGFR agents in combination with other signaling agents and chemotherapies. Since our first publication on lapatinib 10 years ago, we have been excited about the impact of our efforts, and we remain committed to improving the lives of cancer patients. https://aacrjournals.org/mct/article/10/11/2019/90946/The-Discovery-of-Lapatinib-GW572016-Commentary-on

C36H34CLFN4O7S2

753.259169101715

752.154

1187538-35-7

Lapatinib;231277-92-2;Lapatinib ditosylate;388082-77-7; Lapatinib ditosylate monohydrate;388082-78-8;Lapatinib-d4;1184263-99-7;Lapatinib tosylate;1187538-35-7;Lapatinib-d7 dihydrochloride;Lapatinib-d5;2748212-14-6;Lapatinib-d4-1;1184264-15-0

11679357

Typically exists as solid at room temperature

3

12

12

51

1100

0

S(C1C=CC(C)=CC=1)(O)(=O)=O.N(C1C=CC(OCC2C=CC=C(F)C=2)=C(Cl)C=1)C1=NC=NC2=CC=C(C3=CC=C(CNCCS(=O)(=O)C)O3)C=C12

OZDXXJABMOYNGY-UHFFFAOYSA-N

InChI=1S/C29H26ClFN4O4S.C7H8O3S/c1-40(36,37)12-11-32-16-23-7-10-27(39-23)20-5-8-26-24(14-20)29(34-18-33-26)35-22-6-9-28(25(30)15-22)38-17-19-3-2-4-21(31)13-19;1-6-2-4-7(5-3-6)11(8,9)10/h2-10,13-15,18,32H,11-12,16-17H2,1H3,(H,33,34,35);2-5H,1H3,(H,8,9,10)

N-[3-chloro-4-[(3-fluorophenyl)methoxy]phenyl]-6-[5-[(2-methylsulfonylethylamino)methyl]furan-2-yl]quinazolin-4-amine;4-methylbenzenesulfonic acid

Tyverb; Lapatinib (tosylate); CHEMBL1076241; Tykerb; NSC727989; 1187538-35-7; N-[3-chloro-4-[(3-fluorophenyl)methoxy]phenyl]-6-[5-[(2-methylsulfonylethylamino)methyl]furan-2-yl]quinazolin-4-amine;4-methylbenzenesulfonic acid; GW 282974X;

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

May dissolve in DMSO (in most cases), if not, try other solvents such as H2O, Ethanol, or DMF with a minute amount of products to avoid loss of samples

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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 (Please use freshly prepared in vivo formulations for optimal results.)