title: Positive allosteric modulation of AMPA receptors from efficacy to toxicity: the interspecies exposure-response continuum of the novel potentiator PF-4778574.
abstract: α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) positive allosteric modulation (i.e., "potentiation") has been proposed to overcome cognitive impairments in schizophrenia, but AMPAR overstimulation can be excitotoxic. Thus, it is critical to define carefully a potentiator's mechanism-based therapeutic index (TI) and to determine confidently its translatability from rodents to higher-order species. Accordingly, the novel AMPAR potentiator N-{(3R,4S)-3-[4-(5-cyano-2-thienyl)phenyl]tetrahydro-2H-pyran-4-yl}propane-2-sulfonamide (PF-4778574) was characterized in a series of in vitro assays and single-dose animal studies evaluating AMPAR-mediated activities related to cognition and safety to afford an unbound brain compound concentration (Cb,u)-normalized interspecies exposure-response relationship. Because it is unknown which AMPAR subtype(s) may be selectively potentiated for an optimal TI, PF-4778574 binding affinity and functional potency were determined in rodent tissues expected to express a native mixture of AMPAR subunits and their associated proteins to afford composite pharmacological values. Functional activity was also quantified in recombinant cell lines stably expressing human GluA2 flip or flop homotetramers. Procognitive effects of PF-4778574 were evaluated in both rat electrophysiological and nonhuman primate (nhp) behavioral models of pharmacologically induced N-methyl-d-aspartate receptor hypofunction. Safety studies assessed cerebellum-based AMPAR activation (mouse) and motor coordination disruptions (mouse, dog, and nhp), as well as convulsion (mouse, rat, and dog). The resulting empirically derived exposure-response continuum for PF-4778574 defines a single-dose-based TI of 8- to 16-fold for self-limiting tremor, a readily monitorable clinical adverse event. Importantly, the Cb,u mediating each physiological effect were highly consistent across species, with efficacy and convulsion occurring at just fractions of the in vitro-derived pharmacological values.
authors.affiliation: Department of Pharmacokinetics, Pharmacodynamics and Metabolism (C.L.S., R.J.S., S.M.O., J.L.) and the Neuroscience Research Unit (R.S.H., D.K.B., W.E.H., J.T.L., A.N.H., S.L., M.L.W., F.S.M., C.J.S., M.H.), Worldwide Research and Development, Groton Laboratories, Pfizer Inc., Groton, Connecticut.
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Shaffer
authors.forename: Raymond S
authors.initials: RS
authors.lastname: Hurst
authors.forename: Renato J
authors.initials: RJ
authors.lastname: Scialis
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Osgood
authors.forename: Dianne K
authors.initials: DK
authors.lastname: Bryce
authors.forename: William E
authors.initials: WE
authors.lastname: Hoffmann
authors.forename: John T
authors.initials: JT
authors.lastname: Lazzaro
authors.forename: Ashley N
authors.initials: AN
authors.lastname: Hanks
authors.forename: Susan
authors.initials: S
authors.lastname: Lotarski
authors.forename: Mark L
authors.initials: ML
authors.lastname: Weber
authors.forename: JianHua
authors.initials: J
authors.lastname: Liu
authors.forename: Frank S
authors.initials: FS
authors.lastname: Menniti
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Schmidt
authors.forename: Mihály
authors.initials: M
authors.lastname: Hajós
mesh_terms: D000494:Allosteric Regulation / Q000187:drug effects / Q000502:physiology; D000818:Animals; D002478:Cells, Cultured; D004285:Dogs; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology* / Q000627:therapeutic use; D005260:Female; D057809:HEK293 Cells; D006801:Humans; D008252:Macaca fascicularis; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D011597:Psychomotor Performance / Q000187:drug effects / Q000502:physiology; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D018091:Receptors, AMPA / Q000819:agonists* / Q000502:physiology*; D012640:Seizures / Q000503:physiopathology / Q000517:prevention & control; D013876:Thiophenes / Q000494:pharmacology* / Q000627:therapeutic use; D016896:Treatment Outcome
chemical_list: D018690:Excitatory Amino Acid Agonists; C553362:PF-4778574; D018091:Receptors, AMPA; D013876:Thiophenes