Through computationally directed broad screening, a novel 1, 5-diphenylpyrazole (DPP) class of HIV-1 nonnucleoside reverse transcriptase inhibitors (NNRTIs) has been discovered. Compound 2 (PNU-32945) was found to have good activity versus wild-type (IC(50) = 2.3 microM) and delavirdine-resistant P236L (IC(50) = 1.1 microM) reverse transcriptase (RT). Also, PNU-32945 has an ED(50) for inhibition of viral replication in cell cultures of 0.1 microM and was shown to be noncytotoxic with a CC(50) > 10 microM. Structure-activity relationship studies on the 3- and 4-positions of PNU-32945 led to interesting selectivity and activity within the class. In particular, the 3-hydroxyethyl-4-ethyl congener 29 is a potent inhibitor of the P236L mutant (IC(50) = 0.65 microM), whereas it is essentially inactive versus the wild-type enzyme (IC(50) > 50 microM). Furthermore, this compound was significantly more active versus the P236L mutant than delavirdine. The synthesis and RT inhibitory activity of various 3- and 4-substituted analogues are discussed.
CC-1065 (NSC 298223) is a potent new antitumor antibiotic with a unique structure produced by Streptomyces zelensis. Improved production, isolation, and assay methods are described along with physico-chemical properties and antitumor activity. Screening for soil cultures producing agents displaying both cytotoxic activity against L1210 cells in culture and in vivo activity against P388 leukemia in mice afforded a culture, Streptomyces zelensis, producing a new, potent antitumor antibiotic, CC-1065. Its production, in vitro biological activity, microbiological assays, and taxonomy have already been described1) ; a preliminary communication announced the structure2) shown in Fig. 1. Details of the structure determination have recently been described3). A molecular model of CC-1065 displayed a remarkable curvature, shape,
A novel class of bis(heteroaryl)piperazine (BHAP) analogs which possesses the ability to inhibit NNRTI (non-nucleoside reverse transcriptase inhibitor) resistant recombinant HIV-1 reverse transcriptase (RT) and NNRTI resistant variants of HIV-1 has been identified via targeted screening. Further investigation of the structure-activity relationships of close congeners of these novel (alkylamino)piperidine BHAPs (AAP-BHAPs) led to the synthesis of several compounds possessing the desired phenotype (e.g., activity against recombinant RTs carrying the Y181C and P236L substitutions). Further structural modifications were required to inhibit metabolism and modulate solubility in order to obtain compounds with the desired biological profile as well as appropriate pharmaceutical properties. The AAP-BHAPs with the most suitable characteristics were compounds 7, 15, and 36.
From a broad screening program, the 4-hydroxycoumarin phenprocoumon (I) was previously identified as a lead template with HIV protease inhibitory activity. The crystal structure of phenprocoumon/HIV protease complex initiated a structure-based design effort that initially identified the 4-hydroxy-2-pyrone U-96988 (II) as a first-generation clinical candidate for the potential treatment of HIV infection. Based upon the crystal structure of the 4-hydroxy-2-pyrone III/HIV protease complex, a series of analogues incorporating a 5,6-dihydro-4-hydroxy-2-pyrone template were studied. It was recognized that in addition to having the required pharmacophore (the 4-hydroxy group with hydrogen-bonding interaction with the two catalytic aspartic acid residues and the lactone moiety replacing the ubiquitous water molecule in the active site), these 5,6-dihydro-4-hydroxy-2-pyrones incorporated side chains at the C-6 position that appropriately extended into the S1' and S2' subsites of the enzyme active site. The crystal structures of a number of representative 5,6-dihydro-4-hydroxy-2-pyrones complexed with the HIV protease were also determined to provide better understanding of the interaction between the enzyme and these inhibitors to aid the structure-based drug design effort. The crystal structures of the ligands in the enzyme active site did not always agree with the conformations expected from experience with previous pyrone inhibitors. This is likely due to the increased flexibility of the dihydropyrone ring. From this study, compound XIX exhibited reasonably high enzyme inhibitory activity (Ki = 15 nM) and showed antiviral activity (IC50 = 5 microM) in the cell-culture assay. This result provided a research direction which led to the discovery of active 5,6-dihydro-4-hydroxy-2-pyrones as potential agents for the treatment of HIV infection.
A variety of analogues of 1-[4-methoxy-3,5-dimethylbenzyl]-4-[3-(ethylamino)-2-pyridyl]piperazine hydrochloride (U-80493E) were synthesized and evaluated for their inhibition of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT). Replacement of the substituted aryl moiety with various substituted indoles provided bis(heteroaryl)piperazines (BHAPs) that were 10-100-fold more potent than U-80493E. The pyridyl portion of the lead molecule was found to be very sensitive to modifications. Extensive preclinical evaluations of several of these compounds led to the selection of 1-[(5-methoxyindol-2-yl)carbonyl]-4-[3-(ethylamino)-2- pyridyl]piperazine methanesulfonate (U-87201E, atevirdine mesylate) for clinical evaluation.
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