Selective inhibition of human immunodeficiency viruses by racemates and enantiomers of cis-5-fluoro-1-[2-(hydroxymethyl)-1,3-oxathiolan-5-yl]cytosine

Abstract

3'-Dideoxy-S-fluoro-3'-thiacytidine (FTC) has been shown to be a potent and selective compound against human immunodeficiency virus type 1 in acutely infected primary human lymphocytes. FTC is also active against human immunodeficiency virus type 2, simian immunodeficiency virus, and feline immunodeficiency virus in various cell culture systems, including human monocytes. The antiviral activity can be prevented by 2'-deoxycytidine, but not by other natural nucleosides, suggesting that FTC must be phosphorylated to be active and 2'-deoxycytidine kinase is responsible for the phosphorylation. By using chiral columns or enzymatic techniques, the two enantiomers ofFTC were separated. The (-)-(o-enantiomer of FTC was about 20-fold more potent than the (+)-,i-enantiomer against human immunodeficiency virus type 1 in peripheral blood mononuclear cells and was also effective in thymidine kinase-deficient CEM cells. Racemic FEC and its enantiomers were nontoxic to human lymphocytes and other cell lines at concentrations of up to 100 ,uM. Studies with human bone marrow cells indicated that racemic FTC and its (-)-enantiomer had a median inhibitory concentration of >30 FiM. The (+)-enantiomer was significantly more toxic than the (-)-enantiomer to myeloid progenitor cells. The susceptibilities to FTC of pretherapy isolates in comparison with those of posttherapy 3'-azido-3'-deoxythymidine-resistant viruses in human lymphocytes were not substantially different. Similar results were obtained with well-defined 2',3'-dideoxyinosine-and nevirapine-resistant viruses.(-)-FTC-5'-triphosphate competitively inhibited human immunodeficiency virus type 1 reverse transcriptase, with an inhibition constant of 2.9 ,IM, when a poly(I) . oligo(dC)1-24 template primer was used. A two-to threefold decreased affinity was noted for the (+)-enantiomer. By using sequencing analysis, racemic FTC-5'-triphosphate was shown to be a potent DNA chain terminator when human immunodeficiency virus reverse transcriptase was used. These results suggest that further development of the (-)-1-enantiomer of FTC is warranted as an antiviral agent for infections caused by human immunodeficiency viruses.

Structural basis for the binding and incorporation of nucleotide analogs with L -stereochemistry by human DNA polymerase λ

“…Although the L-stereochemistry did not significantly affect the nucleotide binding affinity (1/K d ) based on similar equilibrium dissociation constants (K d ) of L-dCTP and D-dCTP, the chemical modification in the sugar rings of (−)3TC-TP and (−)FTC-TP contributed to their two-to sixfold higher affinity relative to L-dCTP (Table 1). Our kinetic data further indicate that Polλ preferentially incorporated D-dCTP over L-dCTP with the D-stereoselectivity, defined as ( 4 , whereas the D-stereoselectivity was reduced to only 100 and 192 for the incorporation of (−)3TC-TP and (−)FTC-TP, respectively (Table 1). Thus, the chemical changes in the ribose of (−)3TC-TP and (−)FTC-TP relaxed the D-stereoselectivity of Polλ by 100-fold and made these L-nucleotide analogs better substrates than L-dCTP.…”

“…1), possess L-stereochemistry. Both lamivudine and emtricitabine have been shown to be more effective in inhibiting HIV-1 RT and less toxic than their enantiomeric D-isomers (1)(2)(3)(4). In addition, both lamivudine, a potent inhibitor of hepatitis B virus (HBV) (5), and telbivudine, the L-analog of thymidine, are approved drugs for the treatment of HBV infection, whereas emtricitabine is currently in clinical trials for this purpose (6).…”

One Percent Tenofovir Applied Topically to Humanized BLT Mice and Used According to the CAPRISA 004 Experimental Design Demonstrates Partial Protection from Vaginal HIV Infection, Validating the BLT Model for Evaluation of New Microbicide Candidates

“…4). Prior to selection for in vivo efficacy evaluation here, each inhibitor was shown to efficiently inhibit HIV in vitro (3,5,39,43,50,52,54,56). Our experimental approach for testing these six inhibitors was a single dose of the product administered prior to exposure rather than the two doses of drug administered within 24 h as used in CAPRISA 004 (1).…”

“…NSC23766 prevents viral entry from the inside-out by interfering with the structural modifications that occur within the cell during fusion (16,39). The combination of the reverse transcriptase inhibitors FTC-TDF, the inhibitors present in Truvada (3,43), targets postentry viral DNA synthesis. Following the vaginal administration of each inhibitor, treated BLT mice were challenged vaginally with the same dose of HIV-1 JR-CSF as described above for tenofovir.…”

Manzamine B and E and Ircinal A Related Alkaloids from an Indonesian Acanthostrongylophora Sponge and Their Activity against Infectious, Tropical Parasitic, and Alzheimer's Diseases

“…28,29 In Vitro Enzymatic Assays AChE activity was evaluated in vitro essentially as described by Ellman et al 30 using AChE from bovine erythrocytes (Sigma) and acetylthiocholine iodide as substrate. BACE1 activity was determined in a FRET-based assay using human recombinant BACE (Sigma).…”