title: Dipeptide derivatives of AZT: synthesis, chemical stability, activation in human plasma, hPEPT1 affinity, and antiviral activity.
abstract: 5'-O-Dipeptide ester prodrugs of antiviral zidovudine (AZT) were designed to target the human intestinal oligopeptide transporter, hPEPT1, and were evaluated for their stability at pH 7.4 in buffer and in human plasma, affinity toward hPEPT1, cytotoxicity, and antiretroviral activity. The dipeptide esters of AZT undergo cyclization in buffer at pH 7.4 to release the parent drug at a rate that depends on the size of the side chains of the peptide carrier; the prodrug is considerably more stable if bulky beta-branched amino acids such as Ile and Val are present, particularly as C-terminal residues. Incubation in human plasma showed that most of the dipeptide esters of AZT release the parent drug through two aminopeptidase-mediated pathways: 1) stepwise cleavage of each of the amino acids and 2) direct cleavage of the dipeptide-drug ester bond. However, the plasma hydrolysis of Gly-Gly-AZT and Phe-Gly-AZT showed only direct cleavage of the dipeptide-drug ester bond. Substrate half-lives in plasma were again remarkably high when hydrophobic beta-branched amino acids (Val, Ile) were present. The esters were also good substrates for the intestinal oligopeptide transporter hPEPT1 in vitro, with Val-Gly-AZT and Val-Ala-AZT presenting the highest affinity toward the transporter (IC(50): 0.20 and 0.15 mM, respectively). The AZT dipeptide esters were assayed against the IIIB and ROD strains of HIV, and their cytotoxicity was evaluated in MT-4 cells. The selectivity index of the prodrugs was two- to threefold higher than that of AZT for all compounds analyzed. These results point to the potential of dipeptide-based carriers for the development of effective antiviral drug-delivery systems. Val-Ala-AZT appears to combine chemical stability with good affinity for the hPEPT1 transporter and an improved cytotoxicity/antiretroviral index relative to AZT.
authors.affiliation: CIQUP, Departamento de Química, Faculdade de Ciências, Universidade do Porto, R. Campo Alegre 687, 4169-007 Porto, Portugal.
authors.forename: Cledir
authors.initials: C
authors.lastname: Santos
authors.forename: José
authors.initials: J
authors.lastname: Morais
authors.forename: Luís
authors.initials: L
authors.lastname: Gouveia
authors.forename: Erik
authors.initials: E
authors.lastname: de Clercq
authors.forename: Christophe
authors.initials: C
authors.lastname: Pannecouque
authors.forename: Carsten Uhd
authors.initials: CU
authors.lastname: Nielsen
authors.forename: Bente
authors.initials: B
authors.lastname: Steffansen
authors.forename: Rui
authors.initials: R
authors.lastname: Moreira
authors.forename: Paula
authors.initials: P
authors.lastname: Gomes
mesh_terms: D019380:Anti-HIV Agents / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D018938:Caco-2 Cells; D002460:Cell Line; D004151:Dipeptides / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D015195:Drug Design; D004353:Drug Evaluation, Preclinical; D004355:Drug Stability; D015497:HIV-1 / Q000187:drug effects; D015498:HIV-2 / Q000187:drug effects; D006801:Humans; D008826:Microbial Sensitivity Tests; D015394:Molecular Structure; D000074011:Peptide Transporter 1; D011355:Prodrugs / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D013237:Stereoisomerism; D027981:Symporters / Q000187:drug effects* / Q000378:metabolism; D013997:Time Factors; D018675:Toxicity Tests; D015215:Zidovudine / Q000737:chemistry* / Q000494:pharmacology
chemical_list: D019380:Anti-HIV Agents; D004151:Dipeptides; D000074011:Peptide Transporter 1; D011355:Prodrugs; C082186:SLC15A1 protein, human; D027981:Symporters; D015215:Zidovudine