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Research Area
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Description
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Cancer |
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Biological Activity
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Description
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Lapatinib Ditosylate (GW572016, GW2016, Tykerb, Tyverb) is a potent EGFR and ErbB2 inhibitor with IC50 of 10.8 and 9.2 nM, respectively. |
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Targets
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EGFR |
ErbB2 |
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IC50 |
10.8 nM |
9.2 nM [1] |
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In Vitro
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Lapatinib Ditosylate weakly inhibits the activity of ErbB4 with IC50 of 367 nM, and displays >300-fold selectivity for EGFR and ErbB2 over other kinases such as c-Src, c-Raf, MEK, ERK, c-Fms, CDK1, CDK2, p38, Tie-2, and VEGFR2. Lapatinib Ditosylate significantly inhibits receptor autophosphorylation of EGFR and ErbB2 in a dose-dependent manner with IC50 of 170 nM and 80 nM, respectively in HN5 cells; as well as 210 nM and 60 nM, respectively in BT474 cells. Unlike OSI-774 and Iressa (ZD1839) which preferentially inhibit the growth of the EGFR-overexpressing cells, Lapatinib Ditosylate inhibits the growth of both EGFR- and ErbB2-overexpressing cells. Lapatinib Ditosylate displays higher inhibitory activity against EGFR- or ErbB2-overexpressing cells with IC50 of 0.09-0.21 μM, compared with cells expressing low levels of EGFR or ErbB2 with IC50 of 3-12 μM, and exhibits ~100-fold selectivity over the normal fibroblast cells. Lapatinib Ditosylate potently inhibits the outgrowth of EGFR-overexpressing HN5 and A-431 cells, as well as ErbB2-overexpressing BT474 and N87 cells, and significantly induces G1 arrest of HN5 cells and apoptosis of BT474 cells, which are associated with inhibition of AKT phosphorylation. [1] |
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In Vivo
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Oral administration of Lapatinib Ditosylate (~100 mg/kg) twice daily significantly inhibits the growth of BT474 and HN5 xenografts in a dose-dependent manner. [1] |
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Clinical Trials
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A Phase II study of Lapatinib in treating patients with recurrent prostate cancer has been completed. |
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Features
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Protocol
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Kinase Assay
[1]
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| In vitro kinase assays |
The IC50 values for inhibition of enzyme activity are generated by measuring inhibition of phosphorylation of a peptide substrate. The intracellular kinase domains of EGFR and ErbB2 are purified from a baculovirus expression system. EGFR and ErbB2 reactions are performed in 96-well polystyrene round-bottomed plates in a final volume of 45 μL. Reaction mixtures contain 50 mM 4-morpholinepropanesulfonic acid (pH 7.5), 2 mM MnCl2, 10 μM ATP, 1 μCi of [γ33P] ATP/reaction, 50 μM Peptide A [Biotin-(amino hexonoic acid)-EEEEYFELVAKKK-CONH2], 1 mM dithiothreitol, and 1 μL of DMSO containing serial dilutions of Lapatinib beginning at 10 μM. The reaction is initiated by adding the indicated purified type-1 receptor intracellular domain. The amount of enzyme added is 1 pmol/reaction (20 nM). Reactions are terminated after 10 minutes at 23°C by adding 45 μL of 0.5% phosphoric acid in water. The terminated reaction mix (75 μL) is transferred to phosphocellulose filter plates. The plates are filtered and washed three times with 200 μL of 0.5% phosphoric acid. Scintillation cocktail (50 μL) is added to each well, and the assay is quantified by counting in a Packard Topcount. IC50 values are generated from 10-point dose-response curves. |
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Cell Assay
[1]
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| Cell Lines |
HFF, MCF-7, T47D, A-431, HN5, BT474, N87, CaLu-3, HB4a, and HB4a c5.2 |
| Concentrations |
Dissolved in DMSO, final concentrations ~100 μM |
| Incubation Time |
72 hours |
| Methods |
Cells are exposed to various concentrations of Lapatinib for 72 hours. Relative cell number is estimated using methylene blue staining. The absorbance at 620 nm is read in a Spectra microplate reader. Cell death and cell cycle analysis are assessed by propidium iodide staining and antibody detection of incorporated BrdUrd and staining with propidium iodide. |
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Animal Study
[1]
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| Animal Models |
CD-1 nude female mice implanted s.c. with HN5 cells, and C.B-17 SCID female mice implanted s.c. with BT474 cells |
| Formulation |
Formulated in a vehicle of sulfo-butyl-ether-β-cyclodextrin 10% aqueous solution (CD10) |
| Doses |
~100 mg/kg |
| Administration |
Orally twice daily |
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