nsc-614846 and Acquired-Immunodeficiency-Syndrome

1592U89, (-)-(1S,4R)-4-[2-amino-6-(cyclopropylamino)-9H-purin-9-yl]-2-cyclo pentene-1-methanol, is a carbocyclic nucleoside with a unique biological profile giving potent, selective anti-human immunodeficiency virus (HIV) activity. 1592U89 was selected after evaluation of a wide variety of analogs containing a cyclopentene substitution for the 2'-deoxyriboside of natural deoxynucleosides, optimizing in vitro anti-HIV potency, oral bioavailability, and central nervous system (CNS) penetration. 1592U89 was equivalent in potency to 3'-azido-3'-deoxythymidine (AZT) in human peripheral blood lymphocyte (PBL) cultures against clinical isolates of HIV type 1 (HIV-1) from antiretroviral drug-naive patients (average 50% inhibitory concentration [IC50], 0.26 microM for 1592U89 and 0.23 microM for AZT). 1592U89 showed minimal cross-resistance (approximately twofold) with AZT and other approved HIV reverse transcriptase (RT) inhibitors. 1592U89 was synergistic in combination with AZT, the nonnucleoside RT inhibitor nevirapine, and the protease inhibitor 141W94 in MT4 cells against HIV-1 (IIIB). 1592U89 was anabolized intracellularly to its 5'-monophosphate in CD4+ CEM cells and in PBLs, but the di- and triphosphates of 1592U89 were not detected. The only triphosphate found in cells incubated with 1592U89 was that of the guanine analog (-)-carbovir (CBV). However, the in vivo pharmacokinetic, distribution, and toxicological profiles of 1592U89 were distinct from and improved over those of CBV, probably because CBV itself was not appreciably formed from 1592U89 in cells or animals (<2%). The 5'-triphosphate of CBV was a potent, selective inhibitor of HIV-1 RT, with Ki values for DNA polymerases (alpha, beta, gamma, and epsilon which were 90-, 2,900-, 1,200-, and 1,900-fold greater, respectively, than for RT (Ki, 21 nM). 1592U89 was relatively nontoxic to human bone marrow progenitors erythroid burst-forming unit and granulocyte-macrophage CFU (IC50s, 110 microM) and human leukemic and liver tumor cell lines. 1592U89 had excellent oral bioavailability (105% in the rat) and penetrated the CNS (rat brain and monkey cerebrospinal fluid) as well as AZT. Having demonstrated an excellent preclinical profile, 1592U89 has progressed to clinical evaluation in HIV-infected patients.

Topics: Acquired Immunodeficiency Syndrome; Adenosine Deaminase; Administration, Oral; Animals; Anti-HIV Agents; Antiviral Agents; Area Under Curve; Biotransformation; Cells, Cultured; Dideoxynucleosides; Drug Resistance, Microbial; Female; Half-Life; HIV-1; Humans; Injections, Intravenous; Macaca fascicularis; Male; Rats; Structure-Activity Relationship

Carbovir (CBV) is a guanine nucleoside analog with potent in vitro anti-HIV activity. A prodrug of CBV is currently being evaluated in clinical trials as a potential agent for the treatment of AIDS. The ability of CBV to inhibit mitochondrial DNA synthesis in intact CEM cells was evaluated in the present study, because most of the currently available anti-HIV nucleoside analogs have significant toxicities that result from their inhibition of mitochondrial DNA synthesis. No delayed cytotoxicity was observed in CEM cells treated with 50 microM CBV for 4 weeks. In addition, CBV at concentrations as high as 1 mM did not cause a decline in mitochondrial DNA levels and only minimally increased the concentration of lactic acid in the medium. In contrast to these results with CBV, treatment of CEM cells with 0.5 microM 2',3'-dideoxycytidine resulted in delayed cytotoxicity, a decrease in mitochondrial DNA content and increases in lactic acid levels in the medium. These results indicated that treatment of CEM cells with CBV did not result in the inhibition of mitochondrial DNA synthesis and suggested that treatment of AIDS patients with CBV, or a prodrug of CBV, would not result in some of the toxicities seen with the other anti-HIV nucleoside analogs.

Topics: Acquired Immunodeficiency Syndrome; Anti-HIV Agents; Cell Line; Dideoxynucleosides; DNA, Mitochondrial; Drug Evaluation, Preclinical; Humans; Lactic Acid; Mitochondria; Prodrugs; Zalcitabine

Carbocyclic 2',3'-didehydro-2',3'-dideoxyguanosine (Carbovir: NSC 614846), a novel nucleoside analog, emerged as a potent and selective anti-HIV agent from a large screening program conducted by the National Cancer Institute and its contractors. Its hydrolytic stability and its ability to inhibit the infectivity and replication of HIV in T-cells at concentrations of approximately 200- to 400-fold below toxic concentrations make carbovir a top-priority candidate for development as a potential antiretroviral agent in the treatment of AIDS patients.

Topics: Acquired Immunodeficiency Syndrome; Antiviral Agents; Cytopathogenic Effect, Viral; Dideoxynucleosides; HIV; Molecular Structure; Structure-Activity Relationship; Virus Replication; Zalcitabine; Zidovudine