Intracellular Metabolism of 3′-Azido-3′-Deoxythymidine in the Presence of Ganciclovir or Foscarnet

Abstract

SummaryComparisons were made between the intracellular phosphorylation of 3'-azido-3'-deoxythymidine (AZT) alone and in combination with ganciclovir (GCV) or foscarnet (PFA) in lymphocytes, uninfected fibroblasts and CMV-infected fibroblasts. The effects of AZT and the combinations of AZT with GCV or PFA on cellular dNTP pools were also examined.The phosphorylation of AZT was not altered by the presence of GCV or PFA in lymphocytes, and neither AZT nor the combinations of AZT with GCV or PFA changed the levels of cellular dNTP pools in these cells. AZT was phosphorylated to a greater extent in lymphocytes when compared to fibroblasts, but the proportion of AZT di-and triphosphates was greater in fibroblasts.The infection of fibroblasts with CMV enhanced AZT phosphorylation and increased the levels of cellular dNTP pools. GCV caused a specific reduction in AZT phosphorylation in CMV-infected fibroblasts, with a seven-fold drop in AZT triphosphate compared to AZT alone. GCV did not affect AZT phosphorylation in uninfected fibroblasts, nor did GCV reduce the dTTP pool compared to AZT alone. The effects of GCV upon AZT phosphorylation in CMV-infected cells may shed light on the antagonistic effects of GCV upon the anti-HIV activity of AZT, and are of importance for the development of effective combination therapies for the treatment of AIDS patients infected with CMV.

Synthesis and Antiviral Evaluation of SATE-Foscarnet Prodrugs and New Foscarnet—AZT Conjugates

“…The rationale for the PFA-AZT conjugates (7-10; Fig. 2) was the previously reported synergistic anti-HIV effect of PFA and AZT when used in combination (Eriksson & Schinazi, 1989;Koshida et al, 1989;Kong et al, 1991;Palmer et al, 1996). As a consequence, these conjugates could be able to deliver one equivalent of each antivirally active drug.…”

Synthesis and in vitro activities of a new antiviral duplex drug linking Zidovudine (AZT) and Foscarnet (PFA) via an octadecylglycerol residue

“…6,[12][13][14] The suppression of CMV replication was achieved at lower drug concentrations when AZT and PFA were combined than when the drugs were used alone. 15 The first synthesized antiviral molecules linking AZT and PFA were conjugates, in which the carboxyl or phosphonyl group of PFA ester derivatives was directly covalently linked to the 5 0 -hydroxyl group of AZT or other inhibitory dideoxynucleoside analogues.…”

Increased activation of the combination of 3'-azido-3'-deoxythymidine and 2'-deoxy-3'-thiacytidine in the presence of hydroxyurea

“…CEM cells (a human CD4 ϩ lymphoblastoid cell line) were grown as previously described (35)(36)(37). Cells (7 ϫ 10 5 to 9 ϫ 10 5 ml Ϫ1 ) were incubated with clinically relevant concentrations of AZT, 3TC, and HU separately and in combination as follows: (i) 1 M [ 3 H]AZT (specific activity, 440,000 dpm nmol Ϫ1 ) (methyl- 3…”

“…The growth of the cells exposed to HU was reduced by 65% compared to that of cells incubated without drugs or cells incubated with AZT and 3TC without HU. The cells were then harvested, and the nucleotides were extracted with 12% trichloroacetic acid as previously described (21,27,37). In all experiments, the cells were treated identically with respect to time of addition of drugs and length of incubation with drugs.…”

“…When drug metabolites were analyzed, 30-s fractions were collected, 10 ml of scintillation fluid was added to each, and radioactivity was determined with a Beckman LS 1801 scintillation counter. Peaks were identified by retention time on the chromatograph, ratio of absorbance at 254 nm to that at 280 nm, and comparison with previously published data on the elution profile (5,14,(35)(36)(37). Recoveries were calculated by comparison of peak areas of injected samples to those of pure dNTP standards (Sigma Chemical Co., St. Louis, Mo.)…”