title: Stabilization of the N-terminal residues of luteinizing hormone-releasing hormone agonists and the effect on pharmacokinetics.
abstract: To stabilize leuprolide (1) against chymotrypsin and intestinal degradation several agonists of LHRH (2-12), modified at position 1, 2, or 3 and/or containing N-alpha-methyl at positions 1, 2, or 4, were synthesized by SPPS. These agonists were tested in vitro for (a) rat pituitary LHRH receptor binding, (b) LH release from rat pituitary cells, (c) stability against chymotrypsin, and (d) stability against rat intestinal degradation. The clearances of the compounds in the rat were determined using a RIA. Complete stabilization against chymotrypsin (t1/2) and lumenal degradation (T1/2) was achieved with substitution of NMe-Ser4 in leuprolide; however, with an increase in clearance. Substitution with 1-Nal3 increased both t1/2 and T1/2, while substitution with NAc-Sar1 increased only T1/2. [NAcSar1,NMeSer4,D-Trp6,Pro9NHEt]LHRH (12), the doubly stabilized analogue, was tested in the rat by both iv and id administrations, and its bioavailabilities were measured. No significant improvement in id absorption over leuprolide was observed.
authors.affiliation: Pharmaceutical Products Division, Abbott Laboratories, Abbott Park, Illinois 60064.
authors.forename: F
authors.initials: F
authors.lastname: Haviy
authors.forename: T D
authors.initials: TD
authors.lastname: Fitzpatrick
authors.forename: C J
authors.initials: CJ
authors.lastname: Nichols
authors.forename: R E
authors.initials: RE
authors.lastname: Swenson
authors.forename: E N
authors.initials: EN
authors.lastname: Bush
authors.forename: G
authors.initials: G
authors.lastname: Diaz
authors.forename: A
authors.initials: A
authors.lastname: Nguyen
authors.forename: H N
authors.initials: HN
authors.lastname: Nellans
authors.forename: D J
authors.initials: DJ
authors.lastname: Hoffman
authors.forename: H
authors.initials: H
authors.lastname: Ghanbari
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001682:Biological Availability; D002478:Cells, Cultured; D002918:Chymotrypsin / Q000378:metabolism; D010450:Endopeptidases / Q000378:metabolism; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives / Q000378:metabolism* / Q000493:pharmacokinetics; D007408:Intestinal Absorption; D007583:Jejunum / Q000378:metabolism; D016729:Leuprolide / Q000378:metabolism* / Q000493:pharmacokinetics; D008969:Molecular Sequence Data; D051381:Rats; D016339:Spectrometry, Mass, Fast Atom Bombardment
chemical_list: D007987:Gonadotropin-Releasing Hormone; D010450:Endopeptidases; D002918:Chymotrypsin; D016729:Leuprolide