AIDS title: Design of Antiviral Drugs Effective Against the HIV-1 Virus. Recently we have discovered a novel chemotype, the pyridinioalkanoyl thioesters (PATEs) as anti-HIV-1 agents that selectively target the viral nucleocapsid protein zinc fingers. Our efforts during the last year have been devoted to generating compounds with substantially improved invitroantiviral potencies and decreased cytotoxicity. An entirely different class of ligand structures based on simple, aliphatic amino acid amides has been uncovered. More recently, we have generated a new set of anti-HIV compounds by placing an electronegative atom, such as nitrogen, oxygen or sulfur next to the carbonyl opposite the thiol sulfur instead of the carbon atom in thioesters. A series of thiolcarbamates (TICAs) [R-S-C(=O)-NH-R'] and thiolcarbonates (TICOs) [R-S-C(=O)-O-R'] were synthesized, and each new heteroatom was linked with either a pyridinioalkyl or a plain alkyl/aryl group. Thirty compounds with amino acid-based ligands were synthesized and evaluated for inhibition of HIV-1 replication and infectivity. All the compounds of this chemotype showed similar EC50 values (0.16-1.58 200 mM), but exhibited a wide range of cellular toxicity (IC50) values lying between 4 and 200 mM (highest concentration tested). The influence of increasing the hydrophobicity by preparing linear alkyl homologues did not impact on their antiviral potencies. On the other hand, increasing the inductive effect on the carbamylthio bond by substitution with secondary or tertiary carbon improved the cellular toxicity giving good therapeutic indices. The effect of electron withdrawing groups (bromo or carboxy) at the terminus of the carbamoylthio nitrogen was examined, and it was found that bromo compounds resulted in high toxicity values. It appeared that the replacement of the bromo group by a hydrophilic pyridinio moiety resulted in low cellular toxicity and good therapeutic indices. Thus, it appears that the combination of the carbamoylthio moiety and certain substitutents like tertiary butyl and pyridinio at the thiocarbamoyl nitrogen with the carboxamide terminal on the ligand side turned out to yield good antiviral agents with less cytotoxicity. PATE compounds are good inhibitors of HIV-1 replication in TNF a-induced, latently infected U1 and CEM-SS/SK-1 cells, and this results in extensive modification of intracellular HIV-1 precursor polyproteins containing the CCHC zinc finger motif. A significant activity of the novel thiolcarbamates was seen in latently infected U1 monocyte cell lines and CEM-SS/SK-1 cells. The EC50s of these compounds fell in the micromolar range. No cellular toxicity was evident at the highest test doses. Virucidal effects were observed in HeLa CD4 LTR b-gal cells at micromolar concentrations of TICAs. The above compounds that possessed significant inhibitory effect with good therapeutic indices were further evaluated for their ability to eject zinc from purified recombinant NCp7 invitroin a continuous fluorescence-based assay. The test compounds at 10 or 12 mM concentration resulted in nearly quantitative release of zinc from 1 mM NCp7, while addition of 6 mM releases only about 25% of the zinc. The release of zinc occurs at lower concentrations of TICAs than was found for the PATEs studied previously. These results demonstrate that TICAs retain NCp7 reactivity and are more active compared to our earlier described PATEs. Some of the lead compounds were further evaluated for their ability to inhibit a broad range of viruses, ranging from field isolates and drug resistant strains of HIV-1 to HIV-2 and simian immunodeficiency virus (SIV). The discovery of this family of highly potent NCp7 inhibitors holds promise for inactivating all strains of HIV-1 without generating resistant strains.
