Effects of beta-L-3'-azido-3'-deoxythymidine 5'-triphosphate on host and viral DNA polymerases.
We have previously reported that several beta-L-thymidine analogues including beta-L-3'-azido-3'-deoxythymidine (beta-L-AZT), beta-L-3'-fluoro-2',3'-dideoxythymidine (beta-L-FLT) and beta-L-2', 3'-didehydro-2',3'-dideoxythymidine (beta-L-D4T) did not inhibit HIV replication in human peripheral blood mononuclear (PBM) cells whereas their corresponding beta-D-counterparts are known as potent and selective anti-HIV agents [Faraj et al., 1997. Nucleosides and Nucleotides 16, 1287-1290]. In order to gain insight on the lack of antiviral activities of these beta-L-derivatives, in vitro enzymatic steady state studies were conducted in the present study with beta-L-AZT. beta-L-AZT 5'-triphosphate (L-AZTTP) was chemically synthesized and found to moderately inhibit wild-type HIV reverse transcriptase (HIV-1 RT) with a K(i) value of 2 microM; while lacking any inhibitory effect towards human DNA polymerase alpha, beta or gamma. However, the inhibitory effect of L-AZTTP towards HIV-1 RT was very modest (266-fold less potent) when compared to its isomer beta-D-AZT 5'-triphosphate (D-AZTTP) which exhibits a K(i) value of 0.0075 microM and this finding was further confirmed by DNA chain termination assay. These data suggest that the absence of antiviral activity of the parent beta-L-AZT may in part be explained by the poor inhibition of the targeted viral enzyme by L-AZTTP, the active metabolite. Finally, L-AZTTP was found to lack affinity for the mutant RT at position 184 (M184V) demonstrating that this mutation confers resistance not only to beta-L-2',3'-dideoxycytidine analogs as previously reported by our group [Faraj et al., 1994. Antimicrob. Agents Chemother. 38, 2300-2305] but as well as to beta-L-2',3'-dideoxythymidine analogs.
Faraj
A
A
Department of Pharmacology, Center for AIDS Research, The Comprehensive Cancer Center, and Division of Clinical Pharmacology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA. abdesslem.faraj@ccc.uab.edu
El Alaoui
A M
AM
Gosselin
G
G
Imbach
J L
JL
Morrow
C
C
Sommadossi
J P
JP
D019380:Anti-HIV Agents / Q000494:pharmacology; D001345:Autoradiography; D004256:DNA Polymerase I / Q000378:metabolism*; D019951:DNA Polymerase beta / Q000378:metabolism*; D000074002:DNA Polymerase gamma; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism*; D054306:Dideoxynucleotides; D054303:HIV Reverse Transcriptase / Q000037:antagonists & inhibitors* / Q000235:genetics; D015497:HIV-1 / Q000187:drug effects / Q000201:enzymology*; D006801:Humans; D017354:Point Mutation; D013237:Stereoisomerism; D013942:Thymine Nucleotides / Q000494:pharmacology*; D015215:Zidovudine / Q000031:analogs & derivatives* / Q000494:pharmacology*
D019380:Anti-HIV Agents; D054306:Dideoxynucleotides; D013942:Thymine Nucleotides; D015215:Zidovudine; C052873:zidovudine triphosphate; D054303:HIV Reverse Transcriptase; D004256:DNA Polymerase I; D019951:DNA Polymerase beta; D000074002:DNA Polymerase gamma; D004259:DNA-Directed DNA Polymerase