title: Targeting SVCT for enhanced drug absorption: synthesis and in vitro evaluation of a novel vitamin C conjugated prodrug of saquinavir.
abstract: In order to improve oral absorption, a novel prodrug of saquinavir (Saq), ascorbyl-succinic-saquinavir (AA-Su-Saq) targeting sodium dependent vitamin C transporter (SVCT) was synthesized and evaluated. Aqueous solubility, stability and cytotoxicity were determined. Affinity of AA-Su-Saq towards efflux pump P-glycoprotein (P-gp) and recognition of AA-Su-Saq by SVCT were studied. Transepithelial permeability across polarized MDCK-MDR1 and Caco-2 cells were determined. Metabolic stability of AA-Su-Saq in rat liver microsomes was investigated. AA-Su-Saq appears to be fairly stable in both DPBS and Caco-2 cells with half lives of 9.65 and 5.73 h, respectively. Uptake of [(3)H]Saquinavir accelerated by 2.7 and 1.9 fold in the presence of 50 μM Saq and AA-Su-Saq in MDCK-MDR1 cells. Cellular accumulation of [(14)C]AA diminished by about 50-70% relative to control in the presence of 200 μM AA-Su-Saq in MDCK-MDR1 and Caco-2 cells. Uptake of AA-Su-Saq was lowered by 27% and 34% in the presence of 5mM AA in MDCK-MDR1 and Caco-2 cells, respectively. Absorptive permeability of AA-Su-Saq was elevated about 4-5 fold and efflux index reduced by about 13-15 fold across the polarized MDCK-MDR1 and Caco-2 cells. Absorptive permeability of AA-Su-Saq decreased 44% in the presence of 5mM AA across MDCK-MDR1 cells. AA-Su-Saq was devoid of cytotoxicity over the concentration range studied. AA-Su-Saq significantly enhanced the metabolic stability but lowered the affinity towards CYP3A4. In conclusion, prodrug modification of Saq through conjugation to AA via a linker significantly raised the absorptive permeability and metabolic stability. Such modification also caused significant evading of P-gp mediated efflux and CYP3A4 mediated metabolism. SVCT targeted prodrug approach can be an attractive strategy to enhance the oral absorption and systemic bioavailability of anti-HIV protease inhibitors.
authors.affiliation: Division of Pharmaceutical Science, School of Pharmacy, University of Missouri-Kansas City, 2464 Charlotte Street, Kansas City, MO 64108-2718, United States.
authors.forename: Shuanghui
authors.initials: S
authors.lastname: Luo
authors.forename: Zhiying
authors.initials: Z
authors.lastname: Wang
authors.forename: Mitesh
authors.initials: M
authors.lastname: Patel
authors.forename: Varun
authors.initials: V
authors.lastname: Khurana
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Zhu
authors.forename: Dhananjay
authors.initials: D
authors.lastname: Pal
authors.forename: Ashim K
authors.initials: AK
authors.lastname: Mitra
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism; D000818:Animals; D001205:Ascorbic Acid / Q000031:analogs & derivatives* / Q000032:analysis / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism; D001692:Biological Transport; D018938:Caco-2 Cells; D002460:Cell Line; D051544:Cytochrome P-450 CYP3A; D004339:Drug Compounding; D004355:Drug Stability; D004848:Epithelium / Q000378:metabolism; D017320:HIV Protease Inhibitors / Q000032:analysis / Q000138:chemical synthesis* / Q000378:metabolism; D006801:Humans; D026901:Membrane Transport Proteins / Q000378:metabolism; D008862:Microsomes, Liver / Q000378:metabolism; D058990:Molecular Targeted Therapy / Q000379:methods*; D010539:Permeability; D011355:Prodrugs / Q000138:chemical synthesis / Q000378:metabolism*; D051381:Rats; D019258:Saquinavir / Q000031:analogs & derivatives* / Q000032:analysis / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D060347:Sodium-Coupled Vitamin C Transporters / Q000737:chemistry / Q000378:metabolism*; D012995:Solubility; D014815:Vitamins / Q000378:metabolism
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D017320:HIV Protease Inhibitors; D026901:Membrane Transport Proteins; D011355:Prodrugs; D060347:Sodium-Coupled Vitamin C Transporters; D014815:Vitamins; C569745:ascorbyl-succinic-saquinavir; D012964:Sodium; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D019258:Saquinavir; D001205:Ascorbic Acid