ABSTRACT
(+)-2-Aminobicyclo[3.1.0]hexane-2,6-dicarboxylic acid (1), also known as LY354740, is a highly potent and selective agonist for group II metabotropic glutamate receptors (mGlu receptors 2 and 3) tested in clinical trials. It has been shown to block anxiety in the fear-potentiated startle model. Its relatively low bioavailability in different animal species drove the need for an effective prodrug form that would produce a therapeutic response at lower doses for the treatment of anxiety disorders. We have investigated the increase of intestinal absorption of this compound by targeting the human peptide transporter hPepT1 for active transport of di- and tripeptides derived from 1. We have found that oral administration of an N dipeptide derivative of 1 (12a) in rats shows up to an 8-fold increase in drug absorption and a 300-fold increase in potency in the fear-potentiated startle model in rats when compared with the parent drug 1.
Subject(s)
Alanine/analogs & derivatives , Anti-Anxiety Agents/chemical synthesis , Bridged Bicyclo Compounds/chemical synthesis , Dipeptides/chemical synthesis , Prodrugs/chemical synthesis , Receptors, Metabotropic Glutamate/agonists , Administration, Oral , Alanine/administration & dosage , Alanine/chemical synthesis , Alanine/pharmacokinetics , Animals , Anti-Anxiety Agents/pharmacokinetics , Anti-Anxiety Agents/pharmacology , Biological Availability , Bridged Bicyclo Compounds/administration & dosage , Bridged Bicyclo Compounds/pharmacokinetics , Bridged Bicyclo Compounds/pharmacology , Cell Line, Tumor , Cricetinae , Cricetulus , Dipeptides/pharmacokinetics , Dipeptides/pharmacology , Humans , Male , Peptide Transporter 1 , Prodrugs/pharmacokinetics , Prodrugs/pharmacology , Rats , Rats, Sprague-Dawley , Reflex, Startle/drug effects , Stereoisomerism , Structure-Activity Relationship , Symporters/metabolismABSTRACT
The asymmetric synthesis and biological activity of (2S,1'S,2'R,3'R)-2-(2'-carboxy-3'-hydroxymethylcyclopropyl) glycine ((+)-3) is described. This novel C-3' substituted carboxy cyclopropyl glycine is a highly potent group 2 and group 3 mGluR agonist that has proven to be orally active in both fear potentiated startle (animal model for anxiety) and PCP-induced motor activation (animal model for psychosis) assays in rats.
Subject(s)
Glycine/chemical synthesis , Receptors, Metabotropic Glutamate/agonists , Administration, Oral , Animals , Cerebral Cortex/drug effects , Cerebral Cortex/metabolism , Cyclic AMP/biosynthesis , Fear , Glycine/analogs & derivatives , Glycine/chemistry , Glycine/pharmacology , In Vitro Techniques , Male , Motor Activity/drug effects , Rats , Rats, Sprague-Dawley , Reflex, Startle/drug effects , Stereoisomerism , Structure-Activity RelationshipABSTRACT
We describe herein the syntheses and evaluation of a series of C-termini pyridyl containing Phe*-Ala-based BACE inhibitors (5-19). In conjunction with four fixed residues at the P1 (Phe), P1' (Ala), P2' (Val), and P2' cap (Pyr.), rather detailed SAR modifications at P2 and P3 positions were pursued. The promising inhibitors emerging from this SAR investigation, 12 and 17 demonstrated very good enzyme potency (IC(50)=45 nM) and cellular activity (IC(50)=0.4 microM).
Subject(s)
Dipeptides/chemical synthesis , Endopeptidases/metabolism , Protease Inhibitors/chemical synthesis , Amyloid Precursor Protein Secretases , Aspartic Acid Endopeptidases , Cell Line , Dipeptides/toxicity , Humans , Molecular Mimicry , Protease Inhibitors/toxicity , Structure-Activity RelationshipABSTRACT
Beta-amyloid peptides (Abeta) are produced by a sequential cleavage of amyloid precursor protein (APP) by beta- and gamma-secretases. The lack of Abeta production in beta-APP cleaving enzyme (BACE1)(-/-) mice suggests that BACE1 is the principal beta-secretase in mammalian neurons. Transfection of human APP and BACE1 into neurons derived from wild-type and BACE1(-/-) mice supports cleavage of APP at the canonical beta-secretase site. However, these studies also revealed an alternative BACE1 cleavage site in APP, designated as beta', resulting in Abeta peptides starting at Glu11. The apparent inability of human BACE1 to make this beta'-cleavage in murine APP, and vice versa, led to the hypothesis that this alternative cleavage was species-specific. In contrast, the results from human BACE1 transgenic mice demonstrated that the human BACE1 is able to cleave the endogenous murine APP at the beta'-cleavage site. To address this discrepancy, we designed fluorescent resonance energy transfer peptide substrates containing the beta- and beta'-cleavage sites within human and murine APP to compare: (i) the enzymatic efficiency; (ii) binding kinetics of a BACE1 active site inhibitor LY2039911; and (iii) the pharmacological profiles for human and murine recombinant BACE1. Both BACE1 orthologs were able to cleave APP at the beta- and beta'-sites, although with different efficiencies. Moreover, the inhibitory potency of LY2039911 toward recombinant human and native BACE1 from mouse or guinea pig was indistinguishable. In summary, we have demonstrated, for the first time, that recombinant BACE1 can recognize and cleave APP peptide substrates at the postulated beta'-cleavage site. It does not appear to be a significant species specificity to this cleavage.