AZT and AZT-monophosphate Prodrugs Incorporating HIV-protease Substrate Fragment: Synthesis and Evaluation as Specific Drug Delivery Systems

Abstract

With the view to deliver anti-HIV nucleoside and nucleoside-monophosphate (MP) analogues specifically into HIV-infected cells, we synthesized a series of ester and phosphoramidate peptide conjugates of zidovudine (AZT) and of AZT-MP, respectively, wherein the peptide sequences derive from a HIV-protease (PR) hydrolysable substrate. Their in vitro stability with respect to hydrolysis, anti-HIV activity and cytotoxicity, and ability to inhibit the HIV-PR activity were investigated. Concerning the ester AZT-peptide conjugates, their antiviral activity level in thymidine kinase-expressing (TK+) CEM-SS and MT-4 cells was in most cases closely correlated to their hydrolysis rate: the faster the hydrolysis, the closer the anti-HIV activity to that of AZT. None of them was a HIV-PR substrate, indicating that their antiviral activity was not related to their intracellular hydrolysis by this enzyme. None of them inhibited HIV in TK-deficient (TK-) CEM cells, demonstrating that they probably act as prodrugs of AZT. Most of the phosphoramidate peptide conjugates of AZT-MP were rapidly degraded in a physiological buffer into several metabolites including AZT. Their anti-HIV activity in TK+ CEM-SS and MT-4 cells was much lower than that of AZT, indicating that only low amounts of AZT or AZT-MP were released into cells during incubation. Antiviral activities measured on TK- CEM cells for some phosphoramidates suggest that low amounts of AZT-MP could be released intracellularly. However, this AZT-MP release was not initiated by a HIV-PR hydrolysis, as no evidence for peptide cleavage was obtained by HPLC analysis of one representative compound after incubation with HIV-PR.

‘Click’ chemistry synthesis and capillary electrophoresis study of 1,4-linked 1,2,3-triazole AZT-systemin conjugate

“…Various biomolecules have been conjugated to carrier peptides and delivered selectively to their target organs [2,5,6]. Among these molecules are nucleosides and its derivatives, small molecules that are precursors of nucleic acid monomers, hormones and cofactors of many biochemical reactions [11][12][13][14][15][16][17][18].…”

Targeted delivery of lopinavir to HIV reservoirs in the mesenteric lymphatic system by lipophilic ester prodrug approach

“…4C). Previously published report suggests similar tendency for zidovudine prodrugs [51]. To note, the in vitro IC50 cannot be directly translated to in vivo IC50, as LPV is highly plasma protein bound drug (>99% [52]).…”

Antiviral Peptide-Based Conjugates: State of the Art and Future Perspectives

“…Although, in comparison to other covalent linkages, ester bonds do not provide high chemical or plasma stability, they are nonetheless widely used for conjugating drugs to peptides given their relatively simple synthesis and their well-characterized cleavage mechanisms, either by esterases or under acidic conditions [ 26 ]. Ester bond-linked antiviral PDCs have already been mentioned above as anti-herpes agents [ 32 ], and Liotard et al reported higher chemical stability (e.g., hydrolysis resistance) of HIV-targeting ester-conjugated prodrugs compared to phosphoramidate-based analogs [ 33 ]. In most cases, the antiviral activity of these conjugates is correlated to their hydrolysis rates.…”

“…In most cases, the antiviral activity of these conjugates is correlated to their hydrolysis rates. Prodrug conjugates with Boc or Fmoc protection at the CPP N-terminus were generally less stable than those with Z- or Qnc protecting groups [ 33 ]. Despite the authors’ conclusion that the data obtained do not validate their initial hypothesis for designing HIV RT prodrugs, the work offers helpful insights on the importance of the synthetic chemistry used, the position where the conjugation is performed and the overall stability.…”