title: Factors that restrict the cell permeation of cyclic prodrugs of an opioid peptide, part 3: Synthesis of analogs designed to have improved stability to oxidative metabolism.
abstract: Previously, our laboratory reported that cyclic peptide prodrugs of the opioid peptide H-Tyr-D-Ala-Gly-Phe-D-Leu-OH (DADLE) are metabolized by cytochrome P450 (CYP450) enzymes, which limits their systemic exposure after oral dosing to animals. In an attempt to design more metabolically stable cyclic prodrugs of DADLE, we synthesized analogs of DADLE cyclized with a coumarinic acid linker (CA; CA-DADLE), which contained modifications in the amino acid residues known to be susceptible to CYP450 oxidation. Metabolic stability and metabolite identification studies of CA-DADLE and its analogs were then compared using rat liver microsomes (RLM), guinea pig liver microsomes (GPLM), and human liver microsomes (HLM), as well as recombinant human recombinant cytochrome P450 3A4 (hCYP3A4). Similar to the results observed for CA-DADLE, incubation of its analogs with RLM, GPLM, and HLM resulted in monohydroxylation of an amino acid side chain on these cyclic prodrugs. When CA-DADLE was incubated with hCYP3A4, similar oxidative metabolism of the peptide was observed. In contrast, incubation of the CA-DADLE analogs with hCYP3A4 showed that these amino-acid-modified analogs are not substrates for this CYP450 isozyme. These results suggest that the amino-acid-modified analogs of CA-DADLE prepared in this study could be stable to metabolic oxidation by CYP3A4 expressed in human intestinal mucosal cells.
authors.affiliation: Department of Pharmaceutical Chemistry, The University of Kansas, Lawrence, Kansas 66047, USA. Rebecca_Nofsinger@Merck.com
authors.forename: Rebecca
authors.initials: R
authors.lastname: Nofsinger
authors.forename: Tarra
authors.initials: T
authors.lastname: Fuchs-Knotts
authors.forename: Ronald T
authors.initials: RT
authors.lastname: Borchardt
mesh_terms: D000701:Analgesics, Opioid / Q000138:chemical synthesis / Q000378:metabolism*; D000818:Animals; D001711:Biotransformation; D002463:Cell Membrane Permeability; D002626:Chemistry, Pharmaceutical; D051544:Cytochrome P-450 CYP3A / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D015195:Drug Design; D004355:Drug Stability; D016308:Enkephalin, Leucine-2-Alanine / Q000031:analogs & derivatives / Q000138:chemical synthesis / Q000378:metabolism*; D005260:Female; D006168:Guinea Pigs; D006801:Humans; D006900:Hydroxylation; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology; D010084:Oxidation-Reduction; D011355:Prodrugs / Q000138:chemical synthesis / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000378:metabolism; D013379:Substrate Specificity; D013678:Technology, Pharmaceutical / Q000379:methods
chemical_list: D000701:Analgesics, Opioid; D011355:Prodrugs; D011994:Recombinant Proteins; D016308:Enkephalin, Leucine-2-Alanine; D003577:Cytochrome P-450 Enzyme System; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human