title: Probing for improved potency and in vivo bioavailability of excitatory amino acid transporter subtype 1 inhibitors UCPH-101 and UCPH-102: design, synthesis and pharmacological evaluation of substituted 7-biphenyl analogs.
abstract: Uptake of the major excitatory neurotransmitter in the CNS, (S)-glutamate, is mediated by a family of excitatory amino acid transporters (EAAT). Previously we have explored the structure-activity relationship (SAR) of a series of EAAT1 selective inhibitors, leading to the development of the potent inhibitors UCPH-101 and UCPH-102. In the present study, we set out to improve the solubility properties of these EAAT1 inhibitors with the objective to develop analogs more suited as pharmacological tools for in vivo studies of EAAT1 in terms of their bioavailability. A total of 23 novel UCPH-101/102 analogs were designed, synthesized and characterized pharmacologically at EAAT1-3 in a [(3)H]-D-aspartate uptake assay. Most notably, the potent EAAT1 inhibition displayed of UCPH-101 and UCPH-102 was retained in analog 1d in which the napht-1-yl group in the 7-position of UCPH-102 has been replaced by an o-biphenyl moiety. In contrast, EAAT1 activity was dramatically compromised in analogs 1e and 1f comprising m- and p-biphenyl groups as 7-substituents, respectively. Analog 1d displayed low bioavailability after oral administration in rats, and this problem was addressed by the synthesis of a series of analogs with different chloro, fluoro, methoxy, triflouromethyl and carboxy substitution patterns at the o-biphenyl group of 1d (1h-1s) and m- and p-pyridine analogs of 1d (1t and 1v). Unfortunately, all of the modifications resulted in substantial decreased EAAT1 inhibitory activity, which supports the notion of a very lipophilic binding pocket in EAAT1 for the aromatic 7-substituent in these ligands. In conclusion, while we have not succeeded in developing UCPH-101/102 analogs possessing improved bioavailability properties, this study does offer interesting SAR information about this inhibitor class, and analog 1d seems to be an interesting lead for future SAR studies with focus on the development of more potent EAAT1 inhibitors.
authors.affiliation: Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100, Copenhagen, Denmark.
authors.forename: Mette N
authors.initials: MN
authors.lastname: Erichsen
authors.forename: Jeanette
authors.initials: J
authors.lastname: Hansen
authors.forename: Josep A
authors.initials: JA
authors.lastname: Ruiz
authors.forename: Charles S
authors.initials: CS
authors.lastname: Demmer
authors.forename: Bjarke
authors.initials: B
authors.lastname: Abrahamsen
authors.forename: Jesper F
authors.initials: JF
authors.lastname: Bastlund
authors.forename: Christoffer
authors.initials: C
authors.lastname: Bundgaard
authors.forename: Anders A
authors.initials: AA
authors.lastname: Jensen
authors.forename: Lennart
authors.initials: L
authors.lastname: Bunch
mesh_terms: D001578:Benzopyrans / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology*; D001682:Biological Availability; D001713:Biphenyl Compounds / Q000494:pharmacology*; D002851:Chromatography, High Pressure Liquid; D002853:Chromatography, Liquid; D003374:Coumarins / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology*; D050491:Glutamate Plasma Membrane Transport Proteins / Q000037:antagonists & inhibitors*; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry
chemical_list: C579424:2'-amino-7-(diethylamino)-4'-methyl-2,5'-dioxo-5',6',7',8'-tetrahydro-2H,4'H-4,7'-bichromene-3'-carbonitrile; C553295:2-amino-4-(4-methoxyphenyl)-7-(naphthalen-1-yl)-5-oxo-5,6,7,8-tetrahydro-4H-chromene-3-carbonitrile; D001578:Benzopyrans; D001713:Biphenyl Compounds; D003374:Coumarins; D050491:Glutamate Plasma Membrane Transport Proteins