title: The angiogenesis inhibitor SU5416 has long-lasting effects on vascular endothelial growth factor receptor phosphorylation and function.
abstract: SU5416, a selective inhibitor of the tyrosine kinase activity of the vascular endothelial growth factor (VEGF) receptor Flk-1/KDR, is currently in Phase III clinical trials for the treatment of advanced malignancies. In cellular assays, SU5416 inhibits the VEGF-dependent mitogenic/proliferative response of human umbilical vein endothelial cells (HUVECs). In tumor xenograft models, SU5416 inhibits the growth of tumors from a variety of origins by inhibiting tumor angiogenesis. In three different human tumor xenograft models, infrequent (once or twice a week) administration of SU5416 is efficacious despite the fact that it has a short plasma half-life (30 min), which suggests that SU5416 has long-lasting inhibitory activity in vivo. The goal of the present study was to determine the basis for the prolonged activity of SU5416. The results indicate that a short (3 h) exposure to 5 microM SU5416 (to mimic plasma levels of the compound as measured in patients who were receiving SU5416 therapy) produced long-lasting (at least 72 h) inhibition of the VEGF-dependent proliferation of HUVECs in culture, which indicate that SU5416 has long-lasting inhibitory activity in vitro as well as in vivo. SU5416 treatment of HUVECs did not affect surface expression of Flk-1/KDR or the affinity of the receptor for VEGF. Instead, the durability of the in vitro activity of SU5416 was shown to be attributable to its long-lasting ability to specifically inhibit VEGF-dependent phosphorylation of Flk-1/KDR and subsequent downstream signaling, although SU5416 is not an irreversible inhibitor of Flk-1/KDR tyrosine kinase activity. The long-lasting inhibition of cellular responses to VEGF was attributable to the accumulation of SU5416 in cells, as shown using radiolabeled compound, such that inhibitory cellular concentrations of SU5416 are maintained long after the removal of the compound from the medium. The long-lasting inhibitory activity of SU5416 in vitro is consistent with the finding that SU5416 has demonstrated evidence of biological activity in clinical studies when administered twice a week despite a short plasma half-life.
authors.affiliation: SUGEN, Inc., South San Francisco, California 94080, USA. Dirk-Mendel@sugen.com
authors.forename: D B
authors.initials: DB
authors.lastname: Mendel
authors.forename: R E
authors.initials: RE
authors.lastname: Schreck
authors.forename: D C
authors.initials: DC
authors.lastname: West
authors.forename: G
authors.initials: G
authors.lastname: Li
authors.forename: L M
authors.initials: LM
authors.lastname: Strawn
authors.forename: S S
authors.initials: SS
authors.lastname: Tanciongco
authors.forename: S
authors.initials: S
authors.lastname: Vasile
authors.forename: L K
authors.initials: LK
authors.lastname: Shawver
authors.forename: J M
authors.initials: JM
authors.lastname: Cherrington
mesh_terms: D016475:3T3 Cells; D020533:Angiogenesis Inhibitors / Q000493:pharmacokinetics*; D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002462:Cell Membrane / Q000378:metabolism; D002469:Cell Separation; D002478:Cells, Cultured; D016895:Culture Media, Serum-Free / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects; D000939:Epitopes; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007211:Indoles / Q000493:pharmacokinetics*; D007700:Kinetics; D051379:Mice; D008819:Mice, Nude; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009368:Neoplasm Transplantation; D009389:Neovascularization, Pathologic; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011758:Pyrroles / Q000493:pharmacokinetics*; D020794:Receptor Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism*; D017978:Receptors, Growth Factor / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism*; D040262:Receptors, Vascular Endothelial Growth Factor; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D014407:Tumor Cells, Cultured; D014470:Umbilical Cord / Q000166:cytology / Q000187:drug effects
chemical_list: D020533:Angiogenesis Inhibitors; D016895:Culture Media, Serum-Free; D000939:Epitopes; D007211:Indoles; D011758:Pyrroles; D017978:Receptors, Growth Factor; C116890:Semaxinib; D011505:Protein-Tyrosine Kinases; D020794:Receptor Protein-Tyrosine Kinases; D040262:Receptors, Vascular Endothelial Growth Factor; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases