title: Metabolism of 2',3'-dideoxy-2',3'-didehydro-beta-L(-)-5-fluorocytidine and its activity in combination with clinically approved anti-human immunodeficiency virus beta-D(+) nucleoside analogs in vitro.
abstract: 2',3'-Dideoxy-2',3'-didehydro-beta-L(-)-5-fluorocytidine [L(-)Fd4C] has been reported to be a potent inhibitor of the human immunodeficiency virus (HIV) in cell culture. In the present study the antiviral activity of this compound in two-drug combinations and its intracellular metabolism are addressed. The two-drug combination of L(-)Fd4C plus 2',3'-didehydro-2'-3'-dideoxythymidine (D4T, or stavudine) or 3'-azido-3'-deoxythymidine (AZT, or zidovudine) synergistically inhibited replication of HIV in vitro. Additive antiviral activity was observed with L(-)Fd4C in combination with 2',3'-dideoxycytidine (ddC, or zalcitabine) or 2',3'-dideoxyinosine (ddI, or didanosine). This beta-L(-) nucleoside analog has no activity against mitochondrial DNA synthesis at concentrations up to 10 microM. As we previously reported for other beta-L(-) nucleoside analogs, L(-)Fd4C could protect against mitochondrial toxicity associated with D4T, ddC, and ddI. Metabolism studies showed that this drug is converted intracellularly to its mono-, di-, and triphosphate metabolites. The enzyme responsible for monophosphate formation was identified as cytoplasmic deoxycytidine kinase, and the K(m) is 100 microM. L(-)Fd4C was not recognized in vitro by human mitochondrial deoxypyrimidine nucleoside kinase. Also, L(-)Fd4C was not a substrate for deoxycytidine deaminase. L(-)Fd4C 5'-triphosphate served as an alternative substrate to dCTP for incorporation into DNA by HIV reverse transcriptase. The favorable anti-HIV activity and protection from mitochondrial toxicity by L(-)Fd4C in two-drug combinations favors the further development of L(-)Fd4C as an anti-HIV agent.
authors.affiliation: Department of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
authors.forename: G E
authors.initials: GE
authors.lastname: Dutschman
authors.forename: E G
authors.initials: EG
authors.lastname: Bridges
authors.forename: S H
authors.initials: SH
authors.lastname: Liu
authors.forename: E
authors.initials: E
authors.lastname: Gullen
authors.forename: X
authors.initials: X
authors.lastname: Guo
authors.forename: M
authors.initials: M
authors.lastname: Kukhanova
authors.forename: Y C
authors.initials: YC
authors.lastname: Cheng
mesh_terms: D019380:Anti-HIV Agents / Q000378:metabolism / Q000494:pharmacology*; D002460:Cell Line; D000074002:DNA Polymerase gamma; D004272:DNA, Mitochondrial; D004279:DNA, Viral / Q000096:biosynthesis / Q000187:drug effects; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism; D003641:Deamination; D003842:Deoxycytidine Kinase / Q000378:metabolism; D016049:Didanosine / Q000494:pharmacology; D004347:Drug Interactions; D054303:HIV Reverse Transcriptase / Q000037:antagonists & inhibitors / Q000378:metabolism; D015497:HIV-1 / Q000187:drug effects* / Q000502:physiology; D010766:Phosphorylation; D018119:Stavudine / Q000494:pharmacology; D014779:Virus Replication / Q000187:drug effects; D016047:Zalcitabine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D015215:Zidovudine / Q000494:pharmacology
chemical_list: D019380:Anti-HIV Agents; D004272:DNA, Mitochondrial; D004279:DNA, Viral; D015215:Zidovudine; D016047:Zalcitabine; D018119:Stavudine; D003842:Deoxycytidine Kinase; D054303:HIV Reverse Transcriptase; D000074002:DNA Polymerase gamma; D004259:DNA-Directed DNA Polymerase; D016049:Didanosine; C099405:dexelvucitabine