title: Synthesis and in vitro biological evaluation of valine-containing prodrugs derived from clinically used HIV-protease inhibitors.
abstract: In an approach to improve the pharmacological properties and pharmacokinetic profiles of the current protease inhibitors (PIs) used in clinics, and consequently, their therapeutic potential, we performed the synthesis of PI-spacer-valine prodrugs (PI=saquinavir, nelfinavir and indinavir; spacer=-C(O)(CH(2))(5)NH-), and evaluated their in vitro stability with respect to hydrolysis, anti-HIV activity, cytotoxicity, and permeation through a monolayer of Caco-2 cells (used as a model of the intestinal barrier), as compared with their parent PI and first generation of valine-PIs (wherein valine was directly connected through its carboxyl to the PIs). The PI-spacer-valine conjugates were prepared in two steps, in good yields, by condensing an acid derivative of the appropriate protected valine-spacer moiety with the PI, followed by deprotection of the valine protecting group. With respect to hydrolysis, we found that the PI-spacer-valine prodrugs were chemically more stable than the first generation of PI-Val prodrugs. Their stabilities correlated with the low to very low in vitro anti-HIV activity measured for those prodrugs wherein the coupling of valine-spacer residue to the PIs was performed onto the peptidomimetic PI's hydroxyl. Prodrugs wherein the coupling of the valine-spacer residue was performed onto the non-peptidomimetic PI hydroxyl displayed a higher antiviral activity, indicating that these prodrugs are also to some extent anti-HIV drugs by themselves. While the direct conjugation of L-valine to the PIs constituted a most appealing alternative, which improved their absorptive diffusion across Caco-2 cell monolayers and reduced their recognition by efflux carriers, its conjugation to the PIs through the -C(O)(CH(2))(5)NH- spacer was found to inhibit their absorptive and secretory transepithelial transport. This was attributable to a drastic reduction of their passive permeation and/or active transport, indicating that the PI-spacer-valine conjugates are poor substrates of the aminoacid carrier system located at the brush border side of the Caco-2 cell monolayer.
authors.affiliation: Laboratoire de Chimie des Molécules Bioactives et des Arômes, UMR 6001, Université de Nice Sophia-Antipolis, CNRS, Faculté des Sciences, Institut de Chimie de Nice, Nice, France.
authors.forename: Dominique
authors.initials: D
authors.lastname: Roche
authors.forename: Jacques
authors.initials: J
authors.lastname: Greiner
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Aubertin
authors.forename: Pierre
authors.initials: P
authors.lastname: Vierling
mesh_terms: D002851:Chromatography, High Pressure Liquid; D004353:Drug Evaluation, Preclinical; D004355:Drug Stability; D017320:HIV Protease Inhibitors / Q000138:chemical synthesis* / Q000494:pharmacology*; D066298:In Vitro Techniques; D009682:Magnetic Resonance Spectroscopy; D011355:Prodrugs / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology*; D014633:Valine / Q000737:chemistry*
chemical_list: D017320:HIV Protease Inhibitors; D011355:Prodrugs; D014633:Valine