Metabolism of 3′-Azido-3′-Deoxythymidine and 3′-Fluoro-3′-Deoxythymidine in Combination in Human Immunodeficiency Virus Infected Lymphoblastoid Cells

Abstract

SummaryA combination of 3'-azido-3'-deoxythymidine (AZT) with 3'-fluoro-3'-deoxythymidine (FLT) has been shown previously to give synergistic inhibition of human immunodeficiency virus replication and greatly reduced cytotoxicity in vitro. The phosphorylation of the compounds, and their effect upon the natural deoxynucleoside triphosphate pools, were compared in CEM, H9, and HIV-infected H9/ymphoblastoid cells, both for the compounds when used alone and when combined together.Higher levels of FLT triphosphate than AZT triphosphate, and higher levels of AZT monophosphate than FLT monosphosphate, were formed in all cell types. Both compounds were phosphorylated most efficiently in CEM cells, whereas they were least efficiently phosphorylated in infected H9 cells.Owing to competition, the phosphorylation of both analogues was reduced when used in combination, compared to the phosphorylation of the separate compounds. The phosphorylation of the separate compounds was therefore at a maximum and was not increased by combining the compounds. The two compounds competed equally with each other for phosphorylation when used at a ratio of AZT: FLT of 5:1.Both analogues severely reduced the deoxynucleoside triphosphate pools in uninfected and human immunodeficiency virus-infected H9 cells, but not in CEM cells. The effects of the two compounds were similar to those found when the compounds were combined, and thus H9 cells were shown to be much more sensitive to the effects of the analogues upon deoxynucleoside triphosphate pools than CEM cells were.Received

Design of Anti-HIV Compounds from Nucleoside to Nucleoside 5-Triphosphate Analogs. Problems and Perspectives

“…In contrast to the phosphorylation of AZT to AZTMP, the efficiency of conversion of d4T into d4TMP was at least 200-fold less than that for AZTMP [23,24]. However, the efficiency of di-and triphosphrylation of d4TMP is significantly higher compared with that of AZTMP [25].…”

Mechanisms of nucleoside analog antiviral activity and resistance during human immunodeficiency virus reverse transcription

“…Synthesis of the monophosphate forms of d4T and FLT was at least 200-fold less than that of AZT-MP (7,30,67,100). However, the rates of di-and triphosphorylation of d4T-MP and FLT-MP were significantly augmented compared with that of AZT-MP, as indicated by higher ratios of d4T-TP to d4T-MP in CEM cells (7,30,67). These results suggest that a cellular enzyme other than thymidine kinase may catalyze the synthesis of d4T-MP.…”