With the development of targeted therapeutics, especially for small-molecule inhibitors, it is important to understand whether the observed in vivo efficacy correlates with the modulation of desired/intended target in vivo. We have developed a small-molecule inhibitor of all three vascular endothelial growth factor (VEGF) receptors (VEGFR), platelet-derived growth factor receptor, and c-Kit tyrosine kinases, pazopanib (GW786034), which selectively inhibits VEGF-induced endothelial cell proliferation. It has good oral exposure and inhibits angiogenesis and tumor growth in mice. Because bolus administration of the compound results in large differences in C max and C trough , we investigated the effect of continuous infusion of a VEGFR inhibitor on tumor growth and angiogenesis.

Akt kinases 1, 2, and 3 are important regulators of cell survival and have been shown to be constitutively active in a variety of human tumors. GSK690693 is a novel ATP-competitive, low-nanomolar pan-Akt kinase inhibitor. It is selective for the Akt isoforms versus the majority of kinases in other families; however, it does inhibit additional members of the AGC kinase family. It causes dose-dependent reductions in the phosphorylation state of multiple proteins downstream of Akt, including GSK3B, PRAS40, and Forkhead. GSK690693 inhibited proliferation and induced apoptosis in a subset of tumor cells with potency consistent with intracellular inhibition of Akt kinase activity. In immune-compromised mice implanted with human BT474 breast carcinoma xenografts, a single i.p. administration of GSK690693 inhibited GSK3B phosphorylation in a dose-and time-dependent manner. After a single dose of GSK690693, >3 Mmol/L drug concentration in BT474 tumor xenografts correlated with a sustained decrease in GSK3B phosphorylation. Consistent with the role of Akt in insulin signaling, treatment with GSK690693 resulted in acute and transient increases in blood glucose level. Daily administration of GSK690693 produced significant antitumor activity in mice bearing established human SKOV-3 ovarian, LNCaP prostate, and BT474 and HCC-1954 breast carcinoma xenografts. Immunohistochemical analysis of tumor xenografts after repeat dosing with GSK690693 showed reductions in phosphorylated Akt substrates in vivo. These results support further evaluation of GSK690693 as an anticancer agent.

Inhibition of the vascular endothelial growth factor (VEGF) signaling pathway has emerged as one of the most promising new approaches for cancer therapy. We describe herein the key steps starting from an initial screening hit leading to the discovery of pazopanib, N(4)-(2,3-dimethyl-2H-indazol-6-yl)-N(4)-methyl-N(2)-(4-methyl-3-sulfonamidophenyl)-2,4-pyrimidinediamine, a potent pan-VEGF receptor (VEGFR) inhibitor under clinical development for renal-cell cancer and other solid tumors.

The thymidine analog 3'-azido-3'-deoxythymidine (BW A509U; azidothymidine [AZT]) had potent bactericidal activity against many members of the family Enterobacteriaceae, including strains of Escherichia coli, Salmonella typhimurium, Klebsiella pneumoniae, Shigella flexneri, and Enterobacter aerogenes. AZT also had bactericidal activity against Vibrio cholerae and the fish pathogen Vibrio anguillarum. AZT had no activity against Pseudomonas aeruginosa, gram-positive bacteria, anaerobic bacteria, Mycobacterium tuberculosis, nontuberculosis mycobacteria, or,most fungal pathogens. Several lines of evidence indicated that AZT must be activated to the nucleotide level to inhibit cellular metabolism: (i) AZT was a substrate for E. coli thymidine kinase; (ii) spontaneously arising AZT-resistant mutants of E. coli ML-30 and S. typhimurium were deficient in thymidine kinase; and (iii) intact E. coli ML-30 cells converted [3H]AZT to its mono-, di-, and triphosphate metabolites. Of the phosphorylated metabolites, AZT-5'-triphosphate was the most potent inhibitor of replicative DNA synthesis in toluene-permeabilized E. coli pol A mutant cells. AZT-treated E. coli cultures grown in minimal medium contained highly elongated cells consistent with the inhibition of DNA synthesis. AZT-triphosphate was a specific DNA chain terminator in the in vitro DNA polymerization reaction catalyzed by the Klenow fragment of E. coli DNA polymerase I. Thus, DNA chain termination may explain the lethal properties of this compound against susceptible microorganisms.Nucleoside antibiotics have been under investigation for many years (27). Some of the most clinically effective antiviral agents currently in use are purine or pyrimidine nucleoside analogs (24). For example, ribavirin, a synthetic nucleoside similar in structure to guanosine and inosine, has potent in vitro activity against a broad spectrum of viruses, including the epidemic respiratory viruses (3,25). Two effective inhibitors of bacteria are 9-,B-D-arabinofuranosyladenine and 2',3'-dideoxyadenosine. reported the lethality of the former to a purinerequiring strain of Escherichia coli B. In this organism, 9-4-D-arabinofuranosyladenine markedly inhibited DNA synthesis and had virtually no effect upon RNA synthesis. In addition, 2',3'-dideoxyadenosine was shown to be lethal to selected strains of E. coli by irreversibly inhibiting DNA synthesis in susceptible microorganisms (5, 28).As a result of screening synthetic compounds for potential antimicrobial activity, we have observed that compound BW A509U (3'-azido-3'-deoxythymidine, referred to as AZT in this paper; Fig. 1) has potent, bactericidal in vitro activity against various members of the family Enterobacteriaceae. This report describes the extent of the in vitro growthinhibiting activity of AZT and proposes a mechanism to explain its lethal properties. In addition, the antibacterial activity of AZT is discussed in light of the recent finding that this compound inhibits human T-cell lymphotropic virus type III/lymphadenopathy-assoc...