The novel oral Hsp90 inhibitor NVP-HSP990 exhibits potent and broad-spectrum antitumor activities in vitro and in vivo.

A novel oral Hsp90 inhibitor, NVP-HSP990, has been developed and characterized in vitro and in vivo. In vitro, NVP-HSP990 exhibits single digit nanomolar IC(50) values on three of the Hsp90 isoforms (Hsp90α, Hsp90ß, and GRP94) and 320 nanomolar IC(50) value on the fourth (TRAP-1), with selectivity against unrelated enzymes, receptors, and kinases. In c-Met amplified GTL-16 gastric tumor cells, NVP-HSP990 dissociated the Hsp90-p23 complex, depleted client protein c-Met, and induced Hsp70. NVP-HSP990 potently inhibited the growth of human cell lines and primary patient samples from a variety of tumor types. In vivo, NVP-HSP990 exhibits drug-like pharmaceutical and pharmacologic properties with high oral bioavailability. In the GTL-16 xenograft model, a single oral administration of 15 mg/kg of NVP-HSP990 induced sustained downregulation of c-Met and upregulation of Hsp70. In repeat dosing studies, NVP-HSP990 treatment resulted in tumor growth inhibition of GTL-16 and other human tumor xenograft models driven by well-defined oncogenic Hsp90 client proteins. On the basis of its pharmacologic profile and broad-spectrum antitumor activities, clinical trials have been initiated to evaluate NVP-HSP990 in advanced solid tumors.

The discovery of tetrahydro-beta-carbolines as inhibitors of the kinesin Eg5.

A series of tetrahydro-beta-carbolines were identified by HTS as inhibitors of the kinesin Eg5. Molecular modeling and medicinal chemistry techniques were employed to explore the SAR for this series with a focus of removing potential metabolic liabilities and improving cellular potency.

Inhibitors of kinesin motor proteins--research and clinical progress.

Molecules targeting mitosis, and specifically compounds targeting microtubule stability, are important in the treatment of cancer. Unfortunately, the mechanism of action of these agents can cause undesirable toxicities to healthy cells, inducing neurotoxicity and neutropenia in patients. In addition, many of these agents are subject to acquired resistance, usually through increased expression of membrane P-glycoprotein pumps. Due to the clinically proven utility of antimitotic therapeutics, the discovery of new agents with different mechanisms of action which may allow for the development of less toxic oncolytic treatments is highly desirable. This review describes key advances made over the last year toward the design and development of inhibitors of kinesin motor proteins, with particular emphasis placed on non-ATP-competitive, small-molecule inhibitors of kinesin spindle protein (Eg5).

Melanocortin-4 receptor agonists for the treatment of obesity.

The identification of a highly efficacious anti-obesity agent remains an illusive goal. While many avenues of investigation have been pursued, none of the existing compounds claim much more than a 10% reduction in weight in humans (over a one year period with diet and exercise). Nonetheless, the potential reward for fulfilling this unmet medical need has kept interest levels high in the research community. The recent explosion of genetic information has identified numerous potential targets for drug screening. The melanocortin-4 receptor is a promising target and is currently being intensively investigated by many companies and academic research groups.

Agonist-dependent internalization of the human melanocortin-4 receptors in human embryonic kidney 293 cells.

A chimeric protein comprised of melanocortin-4 receptor (MC4R) and the green fluorescent protein (GFP) was created for studying receptor/ligand localization and trafficking. The ligand binding affinities and second messenger stimulation induced by MC4R-GFP closely resembled those of the wild-type receptor, suggesting functional integrity of the chimeric protein. As observed with a confocal microscope, in human embryonic kidney (HEK)-293 cells MC4R/GFP was distributed evenly along the cell membrane. Addition of [Nle4-d-Phe7]-alpha-melanocyte-stimulating hormone (NDP-MSH), a peptide MC4R agonist, induced receptor translocation into intracellular compartments in a time- and concentration-dependent manner. [Ac-Nle-c[Asp-His-d-Nal(2')-Arg-Trp-Lys]-NH2] (SHU9119), a potent MC4R antagonist, completely inhibited NDP-MSH-mediated internalization. MC4R-GFP internalization was unaffected by a protein kinase A inhibitor N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide (H89), but was impaired by pretreatment with inhibitors of endocytosis through clathrin-coated pits, hypertonic sucrose, or concanavalin A. Time-dependent colocalization of MC4R-GFP with rhodamine-transferrin, an early endosome marker, and with LysoTraker, a lysosome marker, was observed after short-term (45 min) and prolonged (20 h) agonist exposure, respectively. Rhodamine-[AcNle-c[Asp-His-d-Phe-Arg-Trp-Lys]-NH2] (MTII), a fluorescent derivative of an MC4R agonist, was found to cointernalize with MC4R-GFP into intracellular vesicles. No significant receptor recycling or segregation from the ligand was observed 60 min after removal of the agonist. In contrast, an antagonist rhodamine-Ac-Cys-Glu-His-(d-Nal)-Arg-Trp-Gly-Cys-Pro-Pro-Lys-Asp-NH2 (HS014) bound to and colocalized with MC4R-GFP on the cell surface and did not stimulate receptor internalization. In sum, these results suggest that MC4R is subject to agonist-dependent endocytosis via clathrin-coated pits. Prolonged agonist exposure directs MC4R into lysosomes, possibly for degradation. Receptor and ligand recycling is not efficient for MC4R in HEK-293 cells.