In vitro activity: AG 18 inhibits EGFR and IR with Ki of 11 μM and 12 mM. AG 18 inhibits EGF-induced EGFR autophoshporylation with IC50 of 15 μM in A431 cells. AG 18 (10 μM) inhibits EGF-induced proliferation of GH3 cells. AG 18 (10 μM) causes significant inhibition of the cell proliferation induced by 10 nM and 1 μM ghrelin. AG 18 (10 μM) blocks the ghrelin-stimulated increase in ERK 1/2 phosphorylation in GH3 cells. AG 18 inhibits the volume-sensitive release of [3H]taurine in primary astrocyte cultures in a dose-dependent manner. AG 18 activates swelling-induced volume-dependent D-[3H]aspartate release from primary astrocytic cultures. AG 18 (300 μM) inhibits TPA-induced stimulation of ICAM-1 expression in a dose dependent manner in A549 epithelial cells. AG 18 (300 μM) also inhibits TPA stimulated NF-kappaB DNA-protein binding and ICAM-1 promoter activity in A549 epithelial cells. AG 18 (300 μM) inhibits TNF-alpha-induced NF-kappaB DNA-protein binding and ICAM-1 promoter activity in a dose dependent manner in A549 epithelial cells. IKK activity is stimulated by both TNF-alpha and TPA, and these effects are inhibited by AG 18 (100 μM) in A549 epithelial cells. AG 18 (10 μM) decreases the potency of 5-HT 4-fold and reduces the maximal contraction to 5-HT in the carotid artery. AG 18 (10 μM) shifts KCl-induced contraction 2-fold and causes the maximum significantly inhibition.

Kinase Assay: WGA-purified EGF receptor from A431 cells (0.5 μg/assay) is activated with EGF (800 nM) for 20 min at 4 ℃. The reaction is initiated by the addition of Mg(Ac)2 (60 mM), Tris-Mes buffer, pH 7.6 (50 mM), and [32P]ATP (20 pM, 5 μCi/assay). The reaction is conducted at either 4 ℃ or 15 ℃ and terminated by addition of sodium dodecyl sulfate (SDS) sample buffer (10% glycerol, 50 mM Tris, pH 6.8, 5% β-mercaptoethanol, and 3% SDS). The samples are run on a 8% SDS polyacrylamide gel (SDS-PAGE) (prepared from 30% acrylamide and 0.8% bis-(acrylamide) and contained 0.375 M Tris, pH 8.8, 0.1% SDS, 0.05% TEMED, and 0.46% ammonium persulfate). The gel is dried and autoradiography is perfromed with Agfa Curix RP2 X-ray film. The relevant radioactive bands are cut and counted in the Cerenkov mode. The fast phase of autophosphorylation continued for another 10 min. The extent of phosphorylation completed in the first 10 s at 15 ℃ comprises 1/3 of the total autophosphorylation signal and probably reflects the phosphorylation of the first site on the receptor. The 10-s interval is therefore chosen for use in subsequent autophosphorylation experiments.

Cell Assay: GH3 cells are plated at 5 × 104 cells/well in media containing 2% charcoal-stripped FCS and various concentrations of ghrelin, desoctanoylated ghrelin and PMA or EGF for 72 hours with the addition of 2 μCi/well [3H]thymidine for a further 6 hours. A time-course of 24 hours, 48 hours and 72 hours is performed for ghrelin stimulation and 72 hours is selected for further experiments. Studies are also performed to investigate the effect of rat ghrelin or desoctanoyl ghrelin-induced proliferation and the effect of U0126, GF109203X, AG 18, wortmannin and H-89 upon ghrelin-induced MAPK stimulation. AG 18 at 10 μM is added 30 min before each treatment. Cells are harvested before counting in the presence of scintillation fluid using a Microbeta 1450 bcounter. Experiments are repeated at least three times.

J Med Chem. 1989 Oct;32(10):2344-52; Am J Physiol. 1999 May;276(5 Pt 1):C1226-30.