PURPOSE: To evaluate the chemical/enzymatic stability and the cell permeation characteristics of the modified coumarinic acid-based cyclic prodrug 2 of DADLE (H-Tyr-D-Ala-Gly-Phe-D-Leu-OH), which has an aldehyde equivalent (oxymethyl) inserted between the phenolic group of the promoiety and the carboxylic acid group of the peptide. METHODS: The rates of the chemical/enzymatic conversion of the oxymethyl-modified prodrug 2 to DADLE were measured by HPLC. The cellular permeation characteristics of DADLE and its oxymethyl-modified prodrug 2 were measured by HPLC using Caco-2 cells, wild type Madin-Darby Canine Kidney cells (MDCK-WT), MDCK cells transfected with human MDR1 gene (MDCK-MDR1), and MDCK cells transfected with human MRP2 gene (MDCK-MRP2) grown onto microporous membranes. RESULTS: The oxymethyl-modified coumarinic acid-based cyclic prodrug 2 degraded chemically to DADLE in a pH-dependent manner, i.e., rates of conversion increased with increasing pH. The prodrug 2 degraded rapidly in rat plasma (t1/2 = 39 min) and rat liver homogenate (t1/2 = 59.2 min), but much slower in Caco-2 cell homogenate (t1/2 = 678.7 min) and human plasma (t1/2 = 264.3 min). In all four cell lines used for transport studies, the flux rates of the oxymethyl prodrug 2 in the basolateral (BL)-to-apical (AP) direction (Papp BL-to-AP) were significantly greater than the flux rates in the AP-to-BL direction (Papp AP-to-BL). The Papp BB-to-AP/Papp AP-to-BL ratios were >116, 35.1, 21.2, and 12.6 in Caco-2, MDCK-MDR1, MDCK-MRP2, and MDCK-WT cells, respectively. The efflux of the modified prodrug could be inhibited by GF120918 (an inhibitor for P-gp) and cyclosporin A (an inhibitor for P-gp and MRP2). CONCLUSIONS: The oxymethyl-modified coumarinic acid-based cyclic prodrug 2 of DADLE could be converted to DADLE in both chemical and enzymatic media. However, the prodrug was a good substrate for both P-gp and MRP2 suggesting that its permeation across intestinal mucosa and blood-brain barrier would be significantly restricted.
PURPOSE: To evaluate the chemical/enzymatic stability and the cell permeation characteristics of the modified coumarinic acid-based cyclic prodrug 2 of DADLE (H-Tyr-D-Ala-Gly-Phe-D-Leu-OH), which has an aldehyde equivalent (oxymethyl) inserted between the phenolic group of the promoiety and the carboxylic acid group of the peptide. METHODS: The rates of the chemical/enzymatic conversion of the oxymethyl-modified prodrug 2 to DADLE were measured by HPLC. The cellular permeation characteristics of DADLE and its oxymethyl-modified prodrug 2 were measured by HPLC using Caco-2 cells, wild type Madin-Darby Canine Kidney cells (MDCK-WT), MDCK cells transfected with humanMDR1 gene (MDCK-MDR1), and MDCK cells transfected with humanMRP2 gene (MDCK-MRP2) grown onto microporous membranes. RESULTS: The oxymethyl-modified coumarinic acid-based cyclic prodrug 2 degraded chemically to DADLE in a pH-dependent manner, i.e., rates of conversion increased with increasing pH. The prodrug 2 degraded rapidly in rat plasma (t1/2 = 39 min) and rat liver homogenate (t1/2 = 59.2 min), but much slower in Caco-2 cell homogenate (t1/2 = 678.7 min) and human plasma (t1/2 = 264.3 min). In all four cell lines used for transport studies, the flux rates of the oxymethyl prodrug 2 in the basolateral (BL)-to-apical (AP) direction (Papp BL-to-AP) were significantly greater than the flux rates in the AP-to-BL direction (Papp AP-to-BL). The PappBB-to-AP/Papp AP-to-BL ratios were >116, 35.1, 21.2, and 12.6 in Caco-2, MDCK-MDR1, MDCK-MRP2, and MDCK-WT cells, respectively. The efflux of the modified prodrug could be inhibited by GF120918 (an inhibitor for P-gp) and cyclosporin A (an inhibitor for P-gp and MRP2). CONCLUSIONS: The oxymethyl-modified coumarinic acid-based cyclic prodrug 2 of DADLE could be converted to DADLE in both chemical and enzymatic media. However, the prodrug was a good substrate for both P-gp and MRP2 suggesting that its permeation across intestinal mucosa and blood-brain barrier would be significantly restricted.
Authors: A Braun; S Hämmerle; K Suda; B Rothen-Rutishauser; M Günthert; S D Krämer; H Wunderli-Allenspach Journal: Eur J Pharm Sci Date: 2000-10 Impact factor: 4.384