title: Selective CNS Uptake of the GCP-II Inhibitor 2-PMPA following Intranasal Administration.
abstract: Glutamate carboxypeptidase II (GCP-II) is a brain metallopeptidase that hydrolyzes the abundant neuropeptide N-acetyl-aspartyl-glutamate (NAAG) to NAA and glutamate. Small molecule GCP-II inhibitors increase brain NAAG, which activates mGluR3, decreases glutamate, and provide therapeutic utility in a variety of preclinical models of neurodegenerative diseases wherein excess glutamate is presumed pathogenic. Unfortunately no GCP-II inhibitor has advanced clinically, largely due to their highly polar nature resulting in insufficient oral bioavailability and limited brain penetration. Herein we report a non-invasive route for delivery of GCP-II inhibitors to the brain via intranasal (i.n.) administration. Three structurally distinct classes of GCP-II inhibitors were evaluated including DCMC (urea-based), 2-MPPA (thiol-based) and 2-PMPA (phosphonate-based). While all showed some brain penetration following i.n. administration, 2-PMPA exhibited the highest levels and was chosen for further evaluation. Compared to intraperitoneal (i.p.) administration, equivalent doses of i.n. administered 2-PMPA resulted in similar plasma exposures (AUC0-t, i.n./AUC0-t, i.p. = 1.0) but dramatically enhanced brain exposures in the olfactory bulb (AUC0-t, i.n./AUC0-t, i.p. = 67), cortex (AUC0-t, i.n./AUC0-t, i.p. = 46) and cerebellum (AUC0-t, i.n./AUC0-t, i.p. = 6.3). Following i.n. administration, the brain tissue to plasma ratio based on AUC0-t in the olfactory bulb, cortex, and cerebellum were 1.49, 0.71 and 0.10, respectively, compared to an i.p. brain tissue to plasma ratio of less than 0.02 in all areas. Furthermore, i.n. administration of 2-PMPA resulted in complete inhibition of brain GCP-II enzymatic activity ex-vivo confirming target engagement. Lastly, because the rodent nasal system is not similar to humans, we evaluated i.n. 2-PMPA also in a non-human primate. We report that i.n. 2-PMPA provides selective brain delivery with micromolar concentrations. These studies support intranasal delivery of 2-PMPA to deliver therapeutic concentrations in the brain and may facilitate its clinical development.
authors.affiliation: Brain Science Institute, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America; Department of Neurology, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America.
authors.forename: Rana
authors.initials: R
authors.lastname: Rais
authors.affiliation: Brain Science Institute, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America.
authors.forename: Krystyna
authors.initials: K
authors.lastname: Wozniak
authors.affiliation: Brain Science Institute, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America.
authors.forename: Ying
authors.initials: Y
authors.lastname: Wu
authors.affiliation: Department of Psychiatry and Behavioral Sciences, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America.
authors.forename: Minae
authors.initials: M
authors.lastname: Niwa
authors.affiliation: Brain Science Institute, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America.
authors.forename: Marigo
authors.initials: M
authors.lastname: Stathis
authors.affiliation: Brain Science Institute, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America.
authors.forename: Jesse
authors.initials: J
authors.lastname: Alt
authors.affiliation: Kurve Technology, Inc., Bothell, Washington, United States of America.
authors.forename: Marc
authors.initials: M
authors.lastname: Giroux
authors.affiliation: Department of Psychiatry and Behavioral Sciences, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America.
authors.forename: Akira
authors.initials: A
authors.lastname: Sawa
authors.affiliation: Brain Science Institute, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America; Department of Molecular and Comparative Pathobiology, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America.
authors.forename: Camilo
authors.initials: C
authors.lastname: Rojas
authors.affiliation: Brain Science Institute, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America; Department of Neurology, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America; Department of Psychiatry and Behavioral Sciences, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America; Department of Neuroscience, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America.
authors.forename: Barbara S
authors.initials: BS
authors.lastname: Slusher
mesh_terms: D000281:Administration, Intranasal; D000818:Animals; D019540:Area Under Curve; D002490:Central Nervous System / Q000378:metabolism*; D002525:Cerebellar Cortex / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D043425:Glutamate Carboxypeptidase II / Q000037:antagonists & inhibitors* / Q000378:metabolism; D005977:Glutarates / Q000008:administration & dosage / Q000032:analysis / Q000493:pharmacokinetics; D006207:Half-Life; D007274:Injections, Intraperitoneal; D008252:Macaca fascicularis; D008297:Male; D009830:Olfactory Bulb / Q000378:metabolism; D009943:Organophosphorus Compounds / Q000008:administration & dosage* / Q000032:analysis / Q000493:pharmacokinetics; D012372:ROC Curve; D051381:Rats; D017208:Rats, Wistar; D013438:Sulfhydryl Compounds / Q000008:administration & dosage / Q000032:analysis / Q000493:pharmacokinetics; D053719:Tandem Mass Spectrometry
chemical_list: C474576:2-(3-mercaptopropyl)pentanedioic acid; C402107:2-(phosphonomethyl)pentanedioic acid; D005977:Glutarates; D009943:Organophosphorus Compounds; D013438:Sulfhydryl Compounds; D043425:Glutamate Carboxypeptidase II