Anti-human immunodeficiency virus type 1 activities of dideoxynucleoside phosphotriester derivatives in primary monocytes/macrophages

Mononucleoside phosphorodithiolates as mononucleotide prodrugs

The synthesis and in vitro anti-HIV activity of a novel series of pronucleotides are reported. These prodrugs were characterized by a phosphorodithiolate structure, incorporating two O-pivaloyl-2-oxyethyl substituents as biolabile phosphate protections. The compounds were obtained following an original one-pot three-step procedure, involving the formation of a phosphorodithioite intermediate which is in situ oxidized. In vitro, comparative anti-HIV evaluations demonstrate that such original prodrugs are able to allow the efficient intracellular release of the corresponding 5'-mononucleotide. The pronucleotide of 2',3'-dideoxyadenosine (ddA) 3 exhibited a very potent antiretroviral effect with 50% effective concentration (EC₅₀) values in nanomolar concentration range in various cell lines. In primary monocytes/macrophages, this derivative was 500 times more potent in inhibiting HIV replication (EC₅₀ 0.23 pM) than ddA and the selectivity index of the prodrug is fifty times higher than the one of the parent nucleoside.

Chemistry of bisSATE mononucleotide prodrugs

On the basis of AZT as a nucleosidic model, the protocols herein describe the synthesis of various bis(S-acyl-2-thioethyl) phosphotriester derivatives. These compounds, bearing transient phosphate-protecting groups, were designed to liberate the corresponding 5'-mononucleotide inside the cell through an esterase-mediated activation process. Two synthetic approaches are presented using either phosphoramidite intermediates or esterification of a nucleoside 5'-monophosphate.

Bis-ketol nucleoside triesters as prodrugs of the antiviral nucleoside triphosphate analogues of 3'-deoxythymidine and 3'-deoxy-2',3'-didehydrothymidine

Derivatives of 3'-deoxythymidine (ddT) and 3'-deoxy-2',3'-didehydrothymidine (d4T) were prepared in which the 5'-hydroxyl group of the nucleoside was esterified to a bis-ketol phosphate. The resulting phosphate triesters are postulated to be prodrugs of the corresponding 5'-mononucleotides, which are formed intracellularly by the hydrolysis of the two ketol ester groups. The triesters were tested for anti-HIV activity with the result that those derived from ddT showed enhanced antiviral activity when compared to the parent nucleoside.

Structure-activity relationships of small phosphopeptides, inhibitors of Grb2 SH2 domain, and their prodrugs

To develop potential antitumor agents directed toward HER2/ErbB2 overexpression in cancer, we have designed inhibitors of the recognition between the phosphotyrosine of the receptor and the SH2 domain of the adaptor protein Grb2. In the first part of the paper, we report the synthesis of mimetics of the constrained (alpha-Me)phosphotyrosine residue such as (alpha-Me)-4-phosphonomethylphenylalanine (-CH2PO3H2), (alpha-Me) 4-phosphonodifluoromethylphenylalanine (-CF2PO3H2), and (alpha-Me)-4-phosphonophenylalanine (-PO3H2). The incorporation of these residues in the mAZ-pTyr-Xaa-Asn-NH2 series provided compounds with very high affinity for the Grb2 SH2 domain, in the 10(-8)-10(-9) range of Kd values. These compounds behave as potent antagonists of the Grb2-Shc interaction. Our results highlight the importance of the doubly negative charge borne by the pY + 1 amino acid in accordance with the interactions observed in the complex crystallized between mAZ-pTyr-(alphaMe)pTyr-Asn-NH2 and the Grb2 SH2 domain. mAZ-pTyr-(alphaMe)pTyr-Asn-NH2 was derivatized as the S-acetyl thioester (SATE) of the phosphotyrosine residues, and its surrogates provided prodrugs with very potent antiproliferative activity on cells overexpressing HER2/ErbB2, with ED50 values amounting to 0.1 microM. Finally a new prodrug is put forth under the form of a monobenzyl ester of phosphate group that is as active as and much easier to synthesize than SATE prodrugs. These compounds show promising activity for further testing on in vivo models.

Comparison of the antiviral activity of hydrophobic amino acid phosphoramidate monoesters of 2'3'-dideoxyadenosine (DDA) and 3'-azido-3'-deoxythymidine (AZT)

A series of hydrophobic, water soluble and non-toxic amino acid phosphoramidate monoesters of dideoxyadenosine (ddA) and 3'-azido-3'-deoxythymidine were shown to inhibit the replication of HIV-1 in human peripheral blood mononuclear cells (PBMC) from two donors. The tryptophan methyl ester phosphoramidates of AZT and ddA were equally potent (EC50S = 0.3-0.4 microM), while the phenyl methyl ester of ddA was 40- to 100- fold more potent than the AZT derivatives. The alaninyl methyl ester of AZT was found to be 70- fold more potent than the ddA derivative. The methyl amide derivatives were found to be 5-20 fold less active than the methyl esters for the ddA series, while for AZT the derivatives were found to be of similar potency or 60- to 166- fold more potent than the methylesters.

Pharmacokinetics of bis(t-butyl-SATE)-AZTMP, a bispivaloylthioethyl prodrug for intracellular delivery of zidovudine monophosphate, in mice

The pharmacokinetics of a bispivaloylthioethyl prodrug of zidovudine monophosphate (AZTMP), bis(t-butyl-SATE)-AZTMP, and intracellular conversion of the prodrug to AZTMP were characterized following intravenous (i.v.) and oral (p.o.) administration of the prodrug to mice. Concentrations of bis(t-butyl-SATE)-AZTMP, AZTMP and zidovudine (AZT) in blood, red blood cells, plasma, brain and lymph nodes were determined by HPLC. Following i.v. administration of bis(t-butyl-SATE)-AZTMP, concentrations of the prodrug declined rapidly with low levels of the prodrug detected until 4 h. Both bis(t-butyl-SATE)-AZTMP and AZTMP were detected in brain 3 min after dosing. AZTMP was found in both plasma and peripheral red blood cells, peaking at approximately 30 min and remaining detectable until 2 h. No AZTMP was detected in lymph nodes. Compared to the pharmacokinetics of AZT following its i.v. administration, i.v. administration of bis(t-butyl-SATE)-AZTMP produced lower peak concentrations of AZT in plasma, peripheral red blood cells, brain and lymph nodes. However, terminal half-lives of AZT were significantly prolonged following administration of the prodrug. Following p.o. administration of bis(t-butyl-SATE)-AZTMP, neither the prodrug nor AZTMP were detectable in whole blood. The conversion of AZT from bis(t-butyl-SATE)-AZTMP in plasma and peripheral red blood cells following p.o administration was 12.1% of that following i.v. administration of the prodrug. Bis(t-butyl-SATE)-AZTMP demonstrated promising potential for intracellular delivery of AZTMP. The prodrug also prolonged the retention of AZT in mice, and particularly increased delivery of AZT to the lymphatic and central nervous systems.

Activities of masked 2',3'-dideoxynucleoside monophosphate derivatives against human immunodeficiency virus in resting macrophages

The anti-human immunodeficiency virus (HIV) activity of aryloxyphosphoramidate protides of a number of anti-HIV nucleoside analogues was assessed in resting primary monocyte-macrophages (M/M). While 2',3'-dideoxythymidine (d4T), 2',3'-dideoxyadenosine (ddA), and 2',3'-dideoxy-2',3'-didehydroadenosine (d4A) protides showed an anti-HIV activity that was 25- to 625-fold greater than the parent nucleotides d4T, ddA, and d4A, respectively, other aryloxyphosphoramidate protides showed similar or even lower anti-HIV activities than their parent compounds. This variable anti-HIV effect is most likely related to the different dynamics of intracellular nucleoside monophosphate release from the protides. Our results indicate the potential advantage of therapeutic use of this approach for some nucleotide analogues to affect HIV replication in M/M, one of the major reservoirs of HIV in vivo.

Development and optimization of anti-HIV nucleoside analogs and prodrugs: A review of their cellular pharmacology, structure-activity relationships and pharmacokinetics

Significant improvements in antiviral therapy have been realized over the past 10 years. Numerous nucleoside analogs, as well as prodrugs of active compounds, have been synthesized and tested for anti-HIV activity. In addition to the five nucleoside analogs currently used clinically for the treatment of HIV infection, a broad spectrum of anti-HIV nucleoside analogs (including 2',3'-dideoxynucleoside analogs, oxathiolanyl 2',3'-dideoxynucleoside analogs, dioxolanyl 2',3'-dideoxynucleoside analogs, carbocyclic 2',3'-dideoxynucleoside analogs and acyclic nucleoside analogs) and their prodrugs (including ester prodrugs, phospholipid prodrugs, dihydropyridine prodrugs, pronucleotides and dinucleotide analogs), targeted at HIV reverse transcriptase, are reviewed with focus on structure-activity relationships, cellular pharmacology and pharmacokinetics. Several of these anti-viral agents show promise in the treatment of AIDS.

Enzymes and protecting group chemistry

Enzymatic protecting group techniques are increasingly finding their use in almost all areas of synthetic organic chemistry. Some of the recent papers have dealt with the use of such protecting groups in combination with classical methods. The modification of known protecting groups to increase the efficiency and selectivity of deprotection is on the rise. The methodology needs to be explored more intensively and systematically to realise its full potential.