Antiviral properties of 3-quinolinecarboxamides: a series of novel non-nucleoside antiherpetic agents.

Novel antiherpetic 3-quinolinecarboxamides were discovered as part of a drug discovery program at Sterling Winthrop Inc. A major goal of this research was to identify novel non-nucleoside agents possessing activity against acyclovir resistant herpes simplex virus. From screening compound libraries in an HSV-2 plaque reduction assay, 1-ethyl-1,4-dihydro-4-oxo-7-(4-pyridinyl)-3-quinolinecarboxamide (1) emerged as an attractive lead structure. By modifying the quinoline ring at the 1-, 2-, 3-, 4-, and 7-positions, analogues were identified that have up to 5-fold increased in vitro potency relative to acyclovir. In a single dose mouse model of infection the 1-(4-FC6H4) analogue 17, one of the most potent derivatives in vitro, displayed comparable oral antiherpetic efficacy to acyclovir at 1/16 the dose; in a multiple dose regimen, however, it was 2-fold less potent. Mechanism of action studies indicate that these new compounds interact with a different, as yet undefined, molecular target than acyclovir.

Keto/enol epoxy steroids as HIV-1 Tat inhibitors: structure-activity relationships and pharmacophore localization.

Inhibition of the HIV-1 nuclear regulatory protein tat could potentially yield particularly useful drugs because it functions as an activator of transcription. It has no known cellular counterpart, and deletions in the tat gene destroy the ability of HIV-1 to replicate. We recently reported that a structurally unique class of tat inhibitors, 3-keto/enol 4,5-alpha-epoxy steroids bearing electron-withdrawing substituents at position 2, specifically inhibit tat-induced gene expression in virus free transfected SW480 cells. In this paper, we report on additional SAR (structure-activity relationships) for the steroid series and the localization of the pharmacophore to the A-ring functionality. There is a weak enantioselective preference for the natural steroid stereochemistry and hints of additional SAR in the electron-withdrawing group. Compound 34a is of particular interest in that it inhibits HIV replication in H9 cells at a concentration equivalent to its inhibitory level in the primary tat assay.

Cyclic variations of 3-quinolinecarboxamides and effects on antiherpetic activity.

Supported by the antiherpetic properties of 3-quinolinecarboxamides and the importance of the planar intramolecular H-bonded beta-keto amide pharmacophore, a series of novel conformationally rigid analogues that contain a heterocyclic bridge between the 3- and 4-positions of the quinoline ring have been evaluated. Two isoxazolo-fused derivatives 17 and 23 displayed good in vitro antiherpetic potency that was similar to that of 1, the 3-quinolinecarboxamide that served as the comparison structure for this study. The pyrazolo, pyrrolo, and pyrimido derivatives showed considerably less or no activity. In vitro activity did not translate to in vivo efficacy. For 17, the lack of in vivo activity is likely a consequence of insufficient plasma drug levels (both Cmax and duration) in mice relative to the MIC versus HSV-2.

Selective inactivation of eukaryotic beta-galactosidase in assays for inhibitors of HIV-1 TAT using bacterial beta-galactosidase as a reporter enzyme.

Bacterial beta-galactosidase is one of several reporter enzymes used in studying the transcriptional activity of eukaryotic promoters. Although it is one of the easiest and least expensive enzymes to assay, its use has been limited because of its low sensitivity, which is due in part to endogenous levels of beta-galactosidase in many eukaryotic cells. In this study, we compared the pH and salt requirements, as well as the heat stability, of bacterial and eukaryotic beta-galactosidase in order to identify conditions which would inhibit the beta-galactosidase enzyme endogenous to eukaryotic cells without adversely affecting the activity of either purified bacterial beta-galactosidase or reporter beta-galactosidase produced after transfection of expression vectors into eukaryotic cells. Heat treatment at 50 degrees C for 1 h inactivated the beta-galactosidase activity endogenous to several eukaryotic cell lines by as much as 40-fold without adversely affecting the activity of bacterial beta-galactosidase. This treatment increased the sensitivity of this reporter enzyme and allowed the development of a rapid and quantifiable screening assay for HIV-1 tat inhibitors.