The alkenyldiarylmethane (ADAM) HIV-1 non-nucleoside reverse transcriptase inhibitors (NNRTIs) are effective anti-HIV agents in cell culture. However, the potential clinical utility of the ADAMs is expected to be limited by the presence of methyl ester moieties that are likely to be metabolized by nonspecific esterases in blood plasma to biologically inactive carboxylic acid derivatives. The present investigation was therefore undertaken to investigate the anti-HIV activities of the ADAMs versus HIV-1(IIIB) and HIV-2(ROD) in MT-4 cells and the stabilities of the biologically active ADAMs in rat plasma. The ADAMs displayed a wide range of metabolic stabilities in rat plasma, with half-lives ranging from 0.9 to 76.6 min. A wide assortment of structural modifications was tolerated, with 18 of the 32 compounds tested displaying EC(50) values between 0.3 and 3.7 microM versus HIV-1(IIIB) in MT-4 cells, 3 compounds in the EC(50) = 13.2-35.4 microM range, and the remaining compounds inactive. Consistent with the mechanism of action of the ADAMs as NNRTIs, they were inactive or displayed comparatively low activity versus HIV-2(ROD). The replacement of the two aromatic methyl ester substituents in one of the most active ADAMs (EC(50) = 0.6 microM) with two methyl thioester groups resulted in an increase in plasma half-life from 5.8 to 55.3 min, while maintaining the antiviral potency at the EC(50) = 1.8 microM level. At the same time, the bis(thioester) modification was less cytotoxic to uninfected MT-4 cells, with a CC(50) of >224 microM versus 160 microM for the parent compound.

In an effort to elucidate a set of structure-activity relationships in the alkenyldiarylmethane (ADAM) series of non-nucleoside reverse transcriptase inhibitors, a number of modifications were made at two locations: (1) the meta positions of the two aromatic rings and (2) the end of the alkenyl chain. Forty-two new ADAMs were synthesized and evaluated for inhibition of the cytopathic effect of HIV-1(RF) in CEM-SS cell culture and for inhibition of HIV-1 reverse transcriptase. The size of the aromatic substituents was found to affect anti-HIV activity, with optimal activity appearing with Cl, CH(3), and Br substituents and with diminished activity occurring with smaller (H and F) or larger (I and CF(3)) substituents. The substituents at the end of the alkenyl chain were also found to influence the antiviral activity, with maximal activity associated with methyl or ethyl ester groups and with diminished activity resulting from substitution with higher esters, amides, sulfides, sulfoxides, sulfones, thioesters, acetals, ketones, carbamates, ureas, and thioureas. Twelve of the new ADAMs displayed submicromolar EC(50) values for inhibition of the cytopathic effect of HIV-1(RF) in CEM-SS cells. Selected ADAMs, 19 and 21, were compared to previously published ADAMs 15 and 17 for antiviral efficacy and activity against the HIV-1 reverse transcriptase enzyme. All four ADAMs were found to inhibit HIV-1 reverse transcriptase enzyme activity, to inhibit the replication of a variety of HIV-1 clinical isolates representing syncytium-inducing, nonsyncytium-inducing, and subtype representative isolates, and to inhibit HIV-1 replication in monocytes. Subsequent assessment against a panel of site-directed reverse transcriptase mutants in NL4-3 demonstrated no effect of the K103N mutation on antiviral efficacy and a slight enhancement (6- to 11-fold) in sensitivity to AZT-resistant viruses. Additionally, ADAMs 19 (44-fold) and 21 (29-fold) were more effective against the A98G mutation (found in association with nevirapine resistance in vitro), and ADAM 21 was 5-fold and 2-fold more potent against the Y181C inactivation mutation than the previously reported ADAMs 15 and 17, respectively. All four ADAMs were tested for efficacy against a multidrug-resistant virus derived from a highly experienced patient expressing resistance to the reverse transcriptase enzyme inhibitors AZT, ddI, 3TC, d4T, foscarnet, and nevirapine, as well as the protease inhibitors indinavir, saquinavir, and nelfinavir. ADAM 21 was 2-fold more potent than ADAM 15 and 6-fold more potent than ADAMs 17 and 19 at preventing virus replication. Thus, we have identified a novel series of reverse transcriptase inhibitors with a favorable profile of antiviral activity against the primary mutation involved in clinical failure of non-nucleoside reverse transcriptase inhibitors, K103N, and that retain activity against a multidrug-resistant virus.