Recently, we disclosed a new class of HCV polymerase inhibitors discovered through high-throughput screening (HTS) of the GlaxoSmithKline proprietary compound collection. This interesting class of 3-(1,1-dioxo-2H-1,2,4-benzothiadiazin-3-yl)-4-hydroxy-2(1H)-quinolinones potently inhibits HCV polymerase enzymatic activity and inhibits the ability of the subgenomic HCV replicon to replicate in Huh-7 cells. This report will focus on the structure-activity relationships (SAR) of substituents on the quinolinone ring, culminating in the discovery of 1-(2-cyclopropylethyl)-3-(1,1-dioxo-2H-1,2,4-benzothiadiazin-3-yl)-6-fluoro-4-hydroxy-2(1H)-quinolinone (130), an inhibitor with excellent potency in biochemical and cellular assays possessing attractive molecular properties for advancement as a clinical candidate. The potential for development and safety assessment profile of compound 130 will also be discussed.

Inhibitors of human methionine aminopeptidase type 2 (hMetAP2) are of interest as potential treatments for cancer. A new class of small molecule reversible inhibitors of hMetAP2 was discovered and optimized, the 4-aryl-1,2,3-triazoles. Compound 24, a potent inhibitor of cobalt-activated hMetAP2, also inhibits human and mouse endothelial cell growth. Using a mouse matrigel model, this reversible hMetAP2 inhibitor was also shown to inhibit angiogenesis in vivo.

HTS of the compound collection for inhibition of the HCV RNA dependent RNA polymerase identified two 168 member N-acyl pyrrolidine combinatorial mixture hits. Deconvolution and expansion of these mixtures by solid phase synthesis to establish initial SAR and identify a potent inhibitor is reported.

The hepatitis C virus (HCV) NS5B protein encodes an RNA-dependent RNA polymerase (RdRp), the primary catalytic enzyme of the HCV replicase complex. We established a biochemical RNA synthesis assay, using purified recombinant NS5B lacking the C-terminal 21 amino acid residues, to identify potential polymerase inhibitors from a high throughput screen of the Glaxo-SmithKline proprietary compound collection. The benzo-1,2,4-thiadiazine compound 1 was found to be a potent, highly specific inhibitor of NS5B. This agent interacts directly with the viral polymerase and inhibits RNA synthesis in a manner noncompetitive with respect to GTP. Furthermore, in the absence of an in vitro-reconstituted HCV replicase assay employing viral and host proteins, the ability of compound 1 to inhibit NS5B-directed viral RNA replication was determined using the Huh7 cell-based HCV replicon system. Compound 1 reduced viral RNA in replicon cells with an IC50 of similar to0.5 muM, suggesting that the inhibitor was able to access the perinuclear membrane and inhibit the polymerase activity in the context of a replicase complex. Preliminary structure-activity studies on compound 1 led to the identification of a modified inhibitor, compound 4, showing an improvement in both biochemical and cell-based potency. Lastly, data are presented suggesting that these compounds interfere with the formation of negative and positive strand progeny RNA by a similar mode of action. Investigations are ongoing to assess the potential utility of such agents in the treatment of chronic HCV disease.

Xenopus laevis melanophores stably expressing 7-transmembrane G-protein-coupled receptors were established and evaluated, either as a primary screening utility for antagonists of the human calcium receptor, or as a screen to assign function to binding inhibitors of human cannabinoid receptors. Stably or transiently expressing melanophores responded selectively to respective effectors of the human calcium, cannabinoid, and neurokinin-1 receptors. Several selective cannabinoid receptor-binding inhibitors of known potency were characterized as agonists or antagonists of the human peripheral cannabinoid (CB(2)) receptor. The results were consistent with changes in cAMP content of hCB(2)-transfected human embryonic kidney (HEK) cells challenged with the same CB(2)-binding antagonists. A stable melanophore cell line expressing the human calcium receptor was used to screen a compound collection directly for functional antagonists, several of which were confirmed as antagonists in secondary screens by stimulating parathyroid hormone (PTH) secretion from bovine parathyroid cells. The percentage of hits in this cell-based screen was reasonably low (1.2%), indicating minimal interference due to toxic effects and validating melanophores as a primary screening modality. Also described is the development of a novel procedure for cryopreservation and reconstitution of cells retaining functional human receptors. ()

In a continuation of our search for potential tumor inhibitors from plants, it was found that the CH2Cl2-MeOH (1:1) extracts from Digitalis purpurea and Penstemon linarioides both showed PKCalpha-inhibitory bioactivity. Bioassay-directed fractionation of the extract from D. purpurea yielded the new, weakly active phenylethanoid glycoside 2-(3-hydroxy-4-methoxy-phenyl)-ethyl-O-(alpha-L-rhamnosyl)-(1-->3) -O- (alpha-L-rhamnosyl)-(1-->6)-4-O-E-feruloyl-beta-D-glucopy ran oside (1) together with the four known compounds calceolarioside A (2), calceolarioside B (3), forsythiaside (4), and plantainoside D (5). The extract from P. linarioides yielded the three known glycosides leucosceptoside A (6), acteoside (7), and poliumoside (8), together with the iridoid plantarenaloside (9). All of the isolated compounds, except compound 9, showed inhibitory activity against PKCalpha with IC50 values (in microM) of 125 (1), 0.6 (2), 4.6 (3), 1.9 (4), 14.8 (5), 19.0 (6), 9.3 (7), and 24.4 (8).

Bioactivity-directed fractionation of the MeCOEt extract of Trichilia emetica (Meliaceae) resulted in the isolation of the limonoids nymania 1 (1), drageana 4 (3), trichilin A (4), rohituka 3 (5), and Tr-B (7) and the novel seco-A protolimonoid 8. Of these, nymania 1 and Tr-B showed selective inhibitory activity toward DNA repair-deficient yeast mutants. The isolation, structure elucidation, 13C NMR spectral assignments, and biological activities of these compounds are reported.

Bioassay-guided fractionation of the CH2Cl2-MeOH extract of Pinus flexilis using an assay for protein kinase C (PKC) inhibitory activity led to the isolation of the two new bioactive diarylheptanoids (3R)-1,7-bis(3, 4-dihydroxyphenyl)-3-(beta-D-glucopyranosyl)heptan-3-ol (1) and its aglycon (3R)-1,7-bis(3,4-dihydroxyphenyl)heptan-3-ol (2), together with the three known bioactive compounds, hirsutenone (3), oregonin (4), and hirsutanonol (5). The IC50 values of compounds 1-5 in the PKC assay were 1.4, 1.6, 1.4, 8.6, and 4.6 microg/mL, respectively.

Members of three classes of pyridinylimidazoles bind with varying affinities to CSBP (p38) kinase which is a member of a stress-induced signal transduction pathway. Based upon SAR and protein homology modeling, the pharmacophore and three potential modes of binding to the enzyme are presented. For a subset of pyridinylimidazoles, binding is shown to correlate with inhibition of CSBP kinase activity, whereas no significant inhibition of PKA, PKC alpha and ERK kinase activity is observed.

The ascidian Lissoclinum japonicum from Palau contained the antimicrobial and antifungal metabolites N,N-dimethyl-5-(methylthio)varacin (6) and 3,4-dimethoxy-6-(2'−N,N-dimethylaminoethyl)-5-(methylthio)benzotrithiane (7), both of which were isolated as the trifluoroacetate salts. An inseparable 2:3 mixture of 5-(methylthio)varacin (8) and the corresponding trithiane 9 was isolated from a different Lissoclinum species from Pohnpei and 3,4-desmethylvaracin (10), isolated as the trifluoroacetate salt, was obtained from a species of Eudistoma from Pohnpei. The pentathiepins and trithianes selectively inhibit protein kinase C.

Two novel spirosesquiterpene aldehydes, corallidictyals A [1] and B [2], were isolated as a mixture from the marine sponge Aka (= Siphonodictyon) coralliphagum, and their structures were determined by detailed spectroscopic methods. These compounds were identified in a screen for inhibitors of protein kinase C.

Twelve coumarins isolated from plants of the Rutaceae collected in Sri Lanka have been subjected to a mechanism-based anticancer bioassay employing DNA repair-deficient and repair-proficient yeasts. Of these, seselin [10] and xanthyletin [11] were found to be active. Seselin also exhibited moderate cytotoxicity.

The cytotoxic sterols 1 and 2, previously isolated from Pseudobersama mossambicensis, have been synthesized in nine steps from stigmasterol, together with seven related sterols. Structure-activity relationships of these sterols in cytotoxicity and DNA-damaging assays are discussed.

Two new cytotoxic cytochalasins were isolated by brine shrimp bioassay-guided fractionation from a culture of the wood inhabiting fungus, Xylaria obovata. Their structures were determined as 19,20-epoxycytochalasin Q (1) and its deacetyl analog 2 by the application of spectroscopic techniques and chemical correlation with cytochalasin R. Acetylation of 2 yielded 1. Both 1 and 2 were cytotoxic but were found to be inactive in an HIV-protease inhibitory assay and a mechanism-based DNA damaging yeast assay.

The cytotoxic alkaloid camptothecin (CPT) and several of its analogues, including the clinically relevant topotecan (TPT), irinotecan (CPT-11), and 9-aminocamptothecin, were evaluated for differential cytotoxic effect and DNA damage induction in multidrug-sensitive (AuxB1) and multidrug-resistant (MDR) (CHRC5) Chinese hamster ovary cells. CPT, 10-hydroxycamptothecin, and 10,11-methylenedioxycamptothecin produced equivalent amounts of cell growth inhibition and/or DNA single-strand breakage in the two cell lines. TPT, SN-38 (the active metabolite of CPT-11), and 9-aminocamptothecin were 12-, 9-, and 10-fold, respectively, less toxic to the MDR than to the wild-type cells. These findings are consistent with differences in yields of DNA single-strand breaks produced in AuxB1 and CHRC5 cells by 2-hr incubations with the various compounds. In both assays, the resistance ratios of the topoisomerase I inhibitors were approximately one-tenth those of known MDR drugs such as vinblastine or amsacrine. Thus, cultured cells that overexpress P-glycoprotein have the potential to develop some level of cross-resistance to all three topoisomerase I inhibitors currently in the clinic. The chemical basis for cross-resistance of cultured MDR cell lines to certain CPT analogues is not yet understood, but is likely more complex than positive charge alone. TPT had a reasonable therapeutic effect on B6D2F1 female mice implanted with MDR sublines of P388 leukemia, compared with its effect on mice implanted with wild-type P388 cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Annals of the New York Academy of SciencesVolume 657, Issue 1 p. 449-451 Down-Regulation of CGRP-Mediated cAMP Accumulation in ras-Transformed 3T3 Fibroblasts NAMBI AIYAR, Corresponding Author NAMBI AIYAR Department of Pharmacology, Discovery SmithKline Beecham Pharmaceuticals, King of Prussia, Pennsylvania 19406-0939Address for correspondence: Nambi Aiyar, Ph.D., SmithKline Beecham Pharmaceuticals, Department of Pharmacology, L510, P.O. Box 1539, King of Prussia, Pennsylvania 19406-0939.Search for more papers by this authorMICHAEL R. MATTERN, MICHAEL R. MATTERN Department of Pharmacology, Discovery SmithKline Beecham Pharmaceuticals, King of Prussia, Pennsylvania 19406-0939Search for more papers by this authorGLENN A. HOFMANN, GLENN A. HOFMANN Department of Pharmacology, Discovery SmithKline Beecham Pharmaceuticals, King of Prussia, Pennsylvania 19406-0939Search for more papers by this authorRICHARD M. EDWARDS, RICHARD M. EDWARDS Department of Pharmacology, Discovery SmithKline Beecham Pharmaceuticals, King of Prussia, Pennsylvania 19406-0939Search for more papers by this authorPONNAL NAMBI, PONNAL NAMBI Department of Pharmacology, Discovery SmithKline Beecham Pharmaceuticals, King of Prussia, Pennsylvania 19406-0939Search for more papers by this author NAMBI AIYAR, Corresponding Author NAMBI AIYAR Department of Pharmacology, Discovery SmithKline Beecham Pharmaceuticals, King of Prussia, Pennsylvania 19406-0939Address for correspondence: Nambi Aiyar, Ph.D., SmithKline Beecham Pharmaceuticals, Department of Pharmacology, L510, P.O. Box 1539, King of Prussia, Pennsylvania 19406-0939.Search for more papers by this authorMICHAEL R. MATTERN, MICHAEL R. MATTERN Department of Pharmacology, Discovery SmithKline Beecham Pharmaceuticals, King of Prussia, Pennsylvania 19406-0939Search for more papers by this authorGLENN A. HOFMANN, GLENN A. HOFMANN Department of Pharmacology, Discovery SmithKline Beecham Pharmaceuticals, King of Prussia, Pennsylvania 19406-0939Search for more papers by this authorRICHARD M. EDWARDS, RICHARD M. EDWARDS Department of Pharmacology, Discovery SmithKline Beecham Pharmaceuticals, King of Prussia, Pennsylvania 19406-0939Search for more papers by this authorPONNAL NAMBI, PONNAL NAMBI Department of Pharmacology, Discovery SmithKline Beecham Pharmaceuticals, King of Prussia, Pennsylvania 19406-0939Search for more papers by this author First published: June 1992 https://doi.org/10.1111/j.1749-6632.1992.tb22796.xCitations: 4AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article. References 1 ROSENFELD, M. G., J. J. MERMOD, S. G. AMARA, L. W. SWANSON, P. E. SAWCHENKO, J. RIVER, W. W. VALE & R. M. EVANS. 1983. Nature 304: 129– 135. 2 DIPETTE, D. J., K. SCHWARZENBERGER, N. KERR & O. B. HOLLAND. 1987. Hypertension 9 (Suppl. 3): 142– 146. 3 KUBOTA, M., J. M. MOSELEY, L. BUTERA, G. L. DUSTING, P. S. MACDONALD & T. J. MARTIN. 1985. Biochem. Biophys. Res. Commun. 132: 88– 94. 4 AIYAR, N., P. NAMBI, E. GRIFFIN, P. BHATNAGAR & G. FEUERSTEIN. 1991. Endocrinology 129: 965– 969. 5 NAMBI, P., M. WHITMAN, F. L. STASSEN & S. T. CROOKE. 1986. J. Pharmacol. Exp. Ther. 237: 143– 146. Citing Literature Volume657, Issue1Calcitonin Gene‐Related Peptide: The First Decade of a Novel Pleiotropic NeuropeptideJune 1992Pages 449-451 ReferencesRelatedInformation

Topotecan (SK&F 104864), a water-soluble analogue of the topoisomerase I inhibitor camptothecin, is currently in Phase II clinical trial for solid tumors. We have characterized topotecan in terms of its effect upon gamma-radiation-induced cell killing. In colony formation experiments, subtoxic concentrations of topotecan (2 microM) potentiated radiation-induced killing of exponentially growing Chinese hamster ovary or P388 murine leukemia cultured cells. Survival curve shoulders were reduced; the slopes of the exponential portions of the curves were decreased to a small extent. D37 and D10 (radiation dose resulting in 37 and 10% survival of colony-forming ability) values were reduced by approximately 60 and 50%, respectively, in the case of Chinese hamster ovary cells. In P388 cells, topotecan reduced D37 by 35 to 40% and D10 by 20 to 25%. Potentiation of radiation-induced cell killing by topotecan was absolutely dependent upon the presence of the topoisomerase I inhibitor during the first few (less than 30) min after irradiation. Association of topoisomerase I with this effect was confirmed in studies of Chinese hamster ovary cells previously made resistant to camptothecin (and cross-resistant to topotecan), resulting in decreased cellular content of topoisomerase I. These cells were found to be 2- to 3-fold hypersensitive to gamma-radiation-induced killing. P388 camptothecin-resistant cells were further sensitized to the lethal effects of ionizing radiation by nontoxic treatment with the topoisomerase II inhibitor novobiocin, consistent with increased dependence of topoisomerase I-deficient cells upon topoisomerase II.

The activity of topoisomerase II and the cellular content of the 170kD and 180kD forms of the enzyme were studied as functions of transformation and growth state by using normal and ras-transformed NIH-3T3 cells. Total topoisomerase II activity, as measured by the unknotting of P4 DNA, was higher in ras-transformed than in normal cells in similar growth states, and was higher in exponentially growing than in plateau cells for both cell lines. Total topoisomerase II levels, as measured by immunoblotting, showed a similar dependence on transformation and growth state. The relative amounts of the 170kD and 180kD forms of the enzyme varied as a function of transformation and growth state. The proportion of 170kD topoisomerase II was higher in ras-transformed than in untransformed cells and depended much less on growth state in the ras-transformed cells. The topoisomerase II activity in extracts of ras-transformed cells was more sensitive to inhibition by teniposide and merbarone, drugs which selectively inhibit the 170kD form of topoisomerase II. The ras-transformed cells were also more sensitive to the cytotoxic effects of these drugs. An increase in the relative cellular content of 170kD topoisomerase II is characteristic of ras-transformed 3T3 cells, and the levels of this form of the enzyme appear to be less dependent on proliferation state than in untransformed cells. The susceptibility of certain tumors to killing by topoisomerase II-directed drugs may be due to a higher proportion of 170kD enzyme as well as a higher level of total topoisomerase II activity.