Thermodynamics and mechanism of the interaction of willardiine partial agonists with a glutamate receptor: implications for drug development.

Understanding the thermodynamics of binding of a lead compound to a receptor can provide valuable information for drug design. The binding of compounds, particularly partial agonists, to subtypes of the α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptor is, in some cases, driven by increases in entropy. Using a series of partial agonists based on the structure of the natural product, willardiine, we show that the charged state of the ligand determines the enthalpic contribution to binding. Willardiines have uracil rings with pKa values ranging from 5.5 to 10. The binding of the charged form is largely driven by enthalpy, while that of the uncharged form is largely driven by entropy. This is due at least in part to changes in the hydrogen bonding network within the binding site involving one water molecule. This work illustrates the importance of charge to the thermodynamics of binding of agonists and antagonists to AMPA receptors and provides clues for further drug discovery.

Synthesis and anti-HIV-1 activity of new MKC-442 analogues with an alkynyl-substituted 6-benzyl group.

Synthesis and antiviral activities are reported of a series of 6-(3-alkynyl benzyl)-substituted analogues of MKC-442 (6-benzyl-1-(ethoxymethyl)-5-isopropyluracil), a highly potent agent against HIV. The 3-alkynyl group is assumed to give a better stacking of the substituted benzyl group to reverse transcriptase (RT) and this was believed to improve antiviral activity against HIV-1. The bromo derivatives, 5-alkyl-6-(3-bromo-benzyl)-1-ethoxymethyl derivatives 7a, b and 5-alkyl-6-(3-bromobenzyl)-1-allyloxymethyl derivatives 9a, b, showed activity against HIV on the same level as their corresponding analogues 10a-d with a 3-trimethylsilylalkynylbenzyl substituent and their desilylated analogues 11a-d. However, they all showed activity against HIV-1 wild type in the range of more than 10fold lower than the one of MKC-442. Moderate activity against Y181C and Y181C + K103N mutated strains was also observed and, in some cases, they were marginally better than those found for MKC-442. A few amino-DABO and S-DABO analogues were also synthesized but they were found to be inactive against HIV.

UFT and its metabolites inhibit cancer-induced angiogenesis. Via a VEGF-related pathway.

Treatment with UFT for spontaneous lung metastasis of murine renal carcinoma (RENCA) after resection of the primary tumor has resulted in significant prolongation of the life span of tumor-bearing animals. UFT inhibited the growth of metastatic nodules in the lung, apparently via decreased density of microvessels in the metastatic foci. Subsequent experiments used dorsal air sac assay to directly trace newly forming microvessels. UFT abrogated the process of angiogenesis, induced by the RENCA cells, in a dose-dependent manner. The inhibitory effect appeared to originate from tegafur, a component of UFT, and from its known metabolites: fluorouracil (5-FU), gamma-hydroxybutyric acid (GHB), and gamma-butyrolactone (GBL). The inhibition of angiogenesis by UFT appeared to be a common phenomenon, also observed in other human cancer cell lines characterized by an excessive production of vascular endothelial growth factor (VEGF)--such as gastric, lung, and colon cancers. In vitro analysis revealed that 5-FU and gamma-hydroxybutyric acid regulated VEGF-dependent responses of human umbilical vein endothelial cells. Dorsal air sac assay revealed that UFT, 5-FU, and gamma-hydroxybutyric acid strongly inhibited the angiogenesis induced by recombinant human VEGF. These data suggest that the antiangiogenic activity of UFT is at least partially associated with an ability of the metabolites of UFT to interfere with VEGF-dependent responses of vascular endothelial cells.