No abstract

The excitatory amino acid transporters (EAATs) are expressed throughout the central nervous system, where they are responsible for the reuptake of the excitatory neurotransmitter (S)-glutamate (Glu). (1) Recently, we have reported the discovery of the first subtype selective EAAT1 inhibitor 2-amino-4-(4-methoxyphenyl)-7-(naphthalen-1-yl)-5-oxo-5,6,7,8-tetrahydro-4H-chromene-3-carbonitrile (UCPH-101) (1b) and presented an introductory structure-activity relationship (SAR) study. (2) Here, we present a detailed SAR by the design, synthesis, and pharmacological evaluation of analogues 1g-1t. By comparison of potencies of 1b, 1h, and 1i versus 1j, it is evident that potency is largely influenced by the chemical nature of the R(1) substituent. The study also demonstrates that any chemical change of the functional groups or a change to the parental scaffold results in the complete loss of inhibitory activity of the compounds at EAAT1. Finally, a bioavailability study of UCPH-101 determined the half-life to be 30 min in serum (rats) but also that it was not able to penetrate the blood-brain barrier to any significant degree.

IntroductionThe 22q11.2 hemizygous microdeletion confers very high risk for neurodevelopmental disorders, including autism and schizophrenia (22q11.2 deletion syndrome [22q11.2DS]). The estimated prevalence is approximately 1 in 2000.1 The International Consortium on Brain and Behaviour in 22q11.2 has recently reported the cumulated prevalence of schizophrenia to be 24% in adolescence and 41% in adulthood.2 Studies of patients with schizophrenia find that 22q11.2 deletion accounts for approximately 0.3% of the cases. Despite massive efforts there is still no coherent understanding of the etiology of schizophrenia -a highly heritable heterogeneous disorder with strong environmental influence. 4,5 Several neurotransmitters are implicated in the disorder: glutamate, 6 γ-aminobutyric acid (GABA), 7 dopamine (DA) 8 and acetylcholine signalling 9 have all been highlighted in the disease etiology and manifestation. The cognitive impairment and negative symptomatology have been related to dysfunction in regulation of glutamate-GABA transmission leading to excitatory-inhibitory imbalances.7 Like in individuals with schizophrenia, 10,11 cognition 12 and information processing is disrupted in children with 22q11.2 deletion, in whom schizophrenia has not (yet) developed.13,14 Given the highly increased risk for schizophrenia and the phenotypic overlap between schizophrenia and the 22q11.2DS, studying the consequence of the 22q11.2 deletion provides a unique opportunity to add to the understanding of the Background: The hemizygous 22q11.2 microdeletion is a common copy number variant in humans. The deletion confers high risk for neuro developmental disorders, including autism and schizophrenia. Up to 41% of deletion carriers experience psychotic symptoms. Methods: We present a new mouse model (Df(h22q11)/+) of the deletion syndrome (22q11.2DS) and report on, to our knowledge, the most comprehensive study undertaken to date in 22q11.2DS models. The study was conducted in male mice. Results: We found elevated postpubertal N-methyl-d-aspartate (NMDA) receptor antagonist-induced hyperlocomotion, age-independent prepulse inhibition (PPI) deficits and increased acoustic startle response (ASR). The PPI deficit and increased ASR were resistant to antipsychotic treatment. The PPI deficit was not a consequence of impaired hearing measured by auditory brain stem responses. The Df(h22q11)/+ mice also displayed increased amplitude of loudness-dependent auditory evoked potentials. Prefrontal cortex and dorsal striatal elevations of the dopamine metabolite DOPAC and increased dorsal striatal expression of the AMPA receptor subunit GluR1 was found. The Df(h22q11)/+ mice did not deviate from wild-type mice in a wide range of other behavioural and biochemical assays. Limitations: The 22q11.2 microdeletion has incomplete penetrance in humans, and the severity of disease depends on the complete genetic makeup in concert with environmental factors. In order to obtain more marked phenotypes reflecting the severe conditions related to 22q11.2DS it...

In the present study, we have elucidated the functional characteristics and mechanism of action of methaqualone (2-methyl-3-o-tolyl-4(3H)-quinazolinone, Quaalude), an infamous sedative-hypnotic and recreational drug from the 1960s-1970s. Methaqualone was demonstrated to be a positive allosteric modulator at human a 1,2,3,5 b 2,3 g 2S GABA A receptors (GABA A Rs) expressed in Xenopus oocytes, whereas it displayed highly diverse functionalities at the a 4,6 b 1,2,3 d GABA A R subtypes, ranging from inactivity (Methaqualone did not interact with the benzodiazepine, barbiturate, or neurosteroid binding sites in the GABA A R. Instead, the compound is proposed to act through the transmembrane b(1) /a (-) subunit interface of the receptor, possibly targeting a site overlapping with that of the general anesthetic etomidate. The negligible activities displayed by methaqualone at numerous neurotransmitter receptors and transporters in an elaborate screening for additional putative central nervous system (CNS) targets suggest that it is a selective GABA A R modulator. The mode of action of methaqualone was further investigated in multichannel recordings from primary frontal cortex networks, where the overall activity changes induced by the compound at 1-100 mM concentrations were quite similar to those mediated by other CNS depressants. Finally, the free methaqualone concentrations in the mouse brain arising from doses producing significant in vivo effects in assays for locomotion and anticonvulsant activity correlated fairly well with its potencies as a modulator at the recombinant GABA A Rs. Hence, we propose that the multifaceted functional properties exhibited by methaqualone at GABA A Rs give rise to its effects as a therapeutic and recreational drug.

A recent article identified five key technical determinants that make substantial contributions to the outcome of drug R&D projects (Lessons learned from the fate of AstraZeneca's drug pipeline: a five-dimensional framework. Nat. Rev. Drug Discov. 13, 419-431 (2014)) 1 . Careful consideration of such determinants might be particularly valuable in the fields of neurology and psychiatry, in which successful drug development has declined precipitously over the past decade. This decline has largely been fuelled by a high failure rate in the translation of preclinical efficacy findings, caused by multiple factors (see Supplementary information S1 (table)), including limited training and poor protocol design, inadequate animal models, insufficiently validated therapeutic targets and problems with data handling and reporting.Here, we focus on three factors that can be addressed immediately in order to re-evaluate the therapeutic potential of older drugs and targets and to increase the probability of success for future preclinical-to-clinical translation: data robustness, data generalizability and target engagement data, a factor that was also highlighted in the recent article 1 . We argue that the many failed clinical trials in neuropsychiatry do not necessarily invalidate the potential of a drug target or an animal model. Rather, these failures indicate a need for improved experimental designs and a robust translational strategy to better inform compound and dose selection for clinical trials. We conclude that many of the drugs and targets in neuropsychiatry that have been discarded because of negative clinical trial outcomes may deserve re-evaluation using contemporary knowledge, methodology and tools.