Purpose
TAK-831 is a highly selective and potent inhibitor of D-amino acid oxidase (DAAO) currently under clinical development for schizophrenia. In this study, a mechanistic multilayer quantitative ...model that parsimoniously connects pharmacokinetics (PK), target occupancy (TO) and D-serine concentrations as a pharmacodynamic (PD) readout was established in mice.
Methods
PK, TO and PD time-profiles were obtained in mice and analyzed by mechanistic binding kinetics model connected with an indirect response model in a step wise fashion. Brain distribution was investigated to elucidate a possible mechanism driving the hysteresis between PK and TO.
Results
The observed nonlinear PK/TO/PD relationship was well captured by mechanistic modeling framework within a wide dose range of TAK-831 in mice. Remarkably different brain distribution was observed between target and reference regions, suggesting that the target-mediated slow binding kinetics rather than slow penetration through the blood brain barrier caused the observed distinct kinetics between PK and TO.
Conclusion
A quantitative mechanistic model for concentration- and time-dependent nonlinear PK/TO/PD relationship was established for TAK-831 in mice with accounting for possible rate-determining process. The established mechanistic modeling framework will provide a quantitative means for multilayer biomarker-assisted clinical development in multiple central nervous system indications.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
In the mammalian central nervous system, transporter‐mediated reuptake may be critical for terminating the neurotransmitter action of d‐serine at the strychnine insensitive glycine site of the NMDA ...receptor. The Na+ independent amino acid transporter alanine–serine–cysteine transporter 1 (Asc‐1) has been proposed to account for synaptosomal d‐serine uptake by virtue of its high affinity for d‐serine and widespread neuronal expression throughout the brain. Here, we sought to validate the contribution of Asc‐1 to d‐serine uptake in mouse brain synaptosomes using Asc‐1 gene knockout (KO) mice. Total 3Hd‐serine uptake in forebrain and cerebellar synaptosomes from Asc‐1 knockout mice was reduced to 34 ± 5% and 22 ± 3% of that observed in wildtype (WT) mice, respectively. When the Na+ dependent transport components were removed by omission of Na+ ions in the assay buffer, d‐serine uptake in knockout mice was reduced to 8 ± 1% and 3 ± 1% of that measured in wildtype mice in forebrain and cerebellum, respectively, suggesting Asc‐1 plays a major role in the Na+ independent transport of d‐serine. Potency determination of d‐serine uptake showed that Asc‐1 mediated rapid high affinity Na+ independent uptake with an IC50 of 19 ± 1 µm. The remaining uptake was mediated predominantly via a low affinity Na+ dependent transporter with an IC50 of 670 ± 300 µm that we propose is the glial alanine–serine–cysteine transporter 2 (ASCT2) transporter. The results presented reveal that Asc‐1 is the only high affinity d‐serine transporter in the mouse CNS and is the predominant mechanism for d‐serine reuptake.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK
Schizophrenia is a chronic and debilitating disease which is thought to arise from a neuro-developmental disorder. Both the stable tubule-only polypeptide (STOP) protein and the
N-methyl-
d-aspartate ...(NMDA) NR1 subunit are involved in neuronal development and physiology. It has therefore been postulated that transgenic mice lacking either the STOP or the NMDAR1 gene would show a ‘schizophrenic-like’ phenotype. Here, STOP knockout and NMDA NR1 hypomorphic mice were assessed in a behavioural measure that can be used to detect schizophrenic-like phenotypes: a change in sensorimotor gating, measured through prepulse inhibition (PPI). STOP knockout mice were further assessed in another measure of ‘schizophrenic-like behaviour’: hyperlocomotion. The PPI deficit exhibited by both the STOP knockout and NMDA knockdown mice could not be reversed by acute treatment with the atyptical antipsychotic, clozapine (1
mg/kg, i.p.) but the hyperlocomotion shown by the STOP knockout mice was reversed with the same acute dose of clozapine.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Non-selective benzodiazepines, such as diazepam, interact with equivalent affinity and agonist efficacy at GABAA receptors containing either an α1, α2, α3 or α5 subunit. However, which of these ...particular subtypes are responsible for the anticonvulsant effects of diazepam remains uncertain. In the present study, we examined the ability of diazepam to reduce pentylenetetrazoLe (PTZ)-induced and maximal electroshock (MES)-induced seizures in mice containing point mutations in single (α1H101R, α2H101R or α5H105R) or multiple (α125H→R) α subunits that render the resulting GABAA receptors diazepam-insensitive. Furthermore, the anticonvulsant properties of diazepam, the α1- and α3-selective compounds zoLpidem and TP003, respectively, and the α2/α3 preferring compound TP13 were studied against PTZ-induced seizures. In the transgenic mice, no single subtype was responsible for the anticonvulsant effects of diazepam in either the PTZ or MES assay and neither the α3 nor α5 subtypes appeared to confer anticonvulsant activity. Moreover, whereas the α1 and α2 subtypes played a modest role with respect to the PTZ assay, they had a negligible role in the MES assay. With respect to subtype-selective compounds, zolpidem and TP003 had much reduced anticonvulsant efficacy relative to diazepam in both the PTZ and MES assays whereas TP13 had high anticonvulsant efficacy in the PTZ but not the MES assay. Taken together, these data not only indicate a role for α2-containing GABAA receptors in mediating PTZ and MES anticonvulsant activity but also suggest that efficacy at more than one subtype is required and that these subtypes act synergistically.
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NUK, OILJ, SAZU, UKNU, UL, UM, UPUK
Non-selective benzodiazepines, such as diazepam, interact with equivalent affinity and agonist efficacy at GABA(A) receptors containing either an alpha1, alpha2, alpha3 or alpha5 subunit. However, ...which of these particular subtypes are responsible for the anticonvulsant effects of diazepam remains uncertain. In the present study, we examined the ability of diazepam to reduce pentylenetetrazoLe (PTZ)-induced and maximal electroshock (MES)-induced seizures in mice containing point mutations in single (alpha1H101R, alpha2H101R or alpha5H105R) or multiple (alpha125H-->R) alpha subunits that render the resulting GABA(A) receptors diazepam-insensitive. Furthermore, the anticonvulsant properties of diazepam, the alpha1- and alpha3-selective compounds zolpidem and TP003, respectively, and the alpha2/alpha3 preferring compound TP13 were studied against PTZ-induced seizures. In the transgenic mice, no single subtype was responsible for the anticonvulsant effects of diazepam in either the PTZ or MES assay and neither the alpha3 nor alpha5 subtypes appeared to confer anticonvulsant activity. Moreover, whereas the alpha1 and alpha2 subtypes played a modest role with respect to the PTZ assay, they had a negligible role in the MES assay. With respect to subtype-selective compounds, zolpidem and TP003 had much reduced anticonvulsant efficacy relative to diazepam in both the PTZ and MES assays whereas TP13 had high anticonvulsant efficacy in the PTZ but not the MES assay. Taken together, these data not only indicate a role for alpha2-containing GABA(A) receptors in mediating PTZ and MES anticonvulsant activity but also suggest that efficacy at more than one subtype is required and that these subtypes act synergistically.
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NUK, OILJ, SAZU, UKNU, UL, UM, UPUK
Abstract
Background
TAK-831 is a potent inhibitor of the DAAO enzyme being developed for the cognitive deficits and negative symptoms of schizophrenia. Inhibition of DAAO results in an increase in ...D-serine, a co-agonist of the NMDA receptor and a full agonist of the δ2 glutamate receptor. Augmentation of NMDA and δ2 glutamate receptor function may be beneficial in schizophrenia. To determine this, rats given TAK-831 were tested in the Novel Object Recognition (NOR) test, a basic cognition test, the Attentional Set Shifting Task (ASST), an animal assay to assess executive function in rodents, and Social Interaction (SI), an animal model of negative symptoms. To determine the impact that a target localized in the cerebellum has on learning, the compound was also profiled in eyeblink conditioning (EBC), a model of cerebellar-based associative learning.
Methods
Rats were given an acute and chronic dose of TAK-831 and cerebrospinal fluid (CSF); cerebellar tissue and plasma were harvested after 6 hours. For NOR, mice were dosed acutely and chronically (14d) with TAK-831 and assessed in their ability to differentiate between novel and previously seen objects after a 4-hour inter-trial interval (ITI). Rats treated with a subchronic phencyclidine (PCP) regimen (2 mg/kg, 7 days bid) showed a deficit in the extra-dimensional shift (EDS) in the ASST. Acute and chronic (14d) doses of TAK-831 were assessed for reversal of the PCP-induced deficit. TAK-831 was dosed acutely and chronically (0.3, 1, 3 mg/kg, po) and assessed for its ability to reverse a naturally occurring SI deficit seen in Balb/c mice. The same dose range was used when the SI deficit was induced by maternal treatment with Poly(I:C). In EBC, a periorbital electrical stimulus was paired with a corneal air puff resulting in classical conditioning. TAK-831 (0.1 and 1 mg/kg, po, 10d chronic dosing) was assessed for its ability to improve acquisition of the conditioned response in the presence and absence of scopolamine.
Results
TAK-831 produced a dose-dependent increase in D-serine levels across CSF, cerebellum, and in plasma. After a 4-hour ITI, vehicle-treated mice were unable to differentiate between a novel and familiar object in NOR. Animals were able to identify the novel object when treated with TAK-831 at 0.3, 1, 3 and 10 mg/kg acute doses and at 0.003, 0.01, 0.03, 0.1, 1.0 and 3 mg/kg chronic doses. TAK-831 was able to reverse the PCP-induced deficit in rats in the EDS in the ASST at 3, 10, and 30 mg/kg acute doses and at 0.1, 1.0 and 10 mg/kg chronic doses. TAK-831 was efficacious in the Balb/c SI model at 1 and 3 mg/kg acute doses and at 0.01, 0.03, 0.1, 1.0 and 10 mg/kg chronic doses; it was efficacious at 3 mg/kg acute dosing in the Poly(I:C) SI model. TAK-831 caused an improvement in both the acquisition of the conditioned response and in reversing the scopolamine-induced deficit at 0.1 and 1 mg/kg in the EBC paradigm.
Discussion
TAK-831 shows utility at a range of doses in animal models associated with negative symptoms and cognitive impairment in schizophrenia. Its efficacy in EBC shows the impact on cerebellar-based learning; this region of the brain is now considered to also be involved in schizophrenia. TAK-831 shows a different range of efficacies pre-clinically, depending on whether the compound is dosed acutely or chronically, indicating a potential plasticity of effect in the brain of preclinical species.
N-methyl-
d
-aspartate (NMDA) receptor hypofunctionality is a well-studied hypothesis for schizophrenia pathophysiology, and daily dosing of the NMDA receptor co-agonist,
d
-serine, in clinical ...trials has shown positive effects in patients. Therefore, inhibition of
d
-amino acid oxidase (DAAO) has the potential to be a new therapeutic approach for the treatment of schizophrenia. TAK-831 (luvadaxistat), a novel, highly potent inhibitor of DAAO, significantly increases
d
-serine levels in the rodent brain, plasma, and cerebrospinal fluid. This study shows luvadaxistat to be efficacious in animal tests of cognition and in a translational animal model for cognitive impairment in schizophrenia. This is demonstrated when luvadaxistat is dosed alone and in conjunction with a typical antipsychotic. When dosed chronically, there is a suggestion of change in synaptic plasticity as seen by a leftward shift in the maximum efficacious dose in several studies. This is suggestive of enhanced activation of NMDA receptors in the brain and confirmed by modulation of long-term potentiation after chronic dosing. DAAO is highly expressed in the cerebellum, an area of increasing interest for schizophrenia, and luvadaxistat was shown to be efficacious in a cerebellar-dependent associative learning task. While luvadaxistat ameliorated the deficit seen in sociability in two different negative symptom tests of social interaction, it failed to show an effect in endpoints of negative symptoms in clinical trials. These results suggest that luvadaxistat potentially could be used to improve cognitive impairment in patients with schizophrenia, which is not well addressed with current antipsychotic medications.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Selective antagonism of N-methyl-d-aspartate (NMDA) 2B subunit containing receptors has been suggested to have potential therapeutic application for multiple CNS disorders. The amino terminal NR2B ...residues 1 to 282 were found to be both necessary and sufficient for the binding and function of highly NR2B subunit specific antagonists like ifenprodil and CP-101,606. Using a genetic approach in mice, we successfully replaced the murine NR2B gene function by “knocking-in” (KI) a chimeric human NR2A/B cDNA containing the minimal domain abolishing ifenprodil binding into the endogenous NR2B locus. Patch-clamp recording from hippocampal cultures of the NR2B KI mice demonstrated that their NMDA receptors have reduced sensitivity to both ifenprodil and CP-101,606, as predicted, but also have a lower affinity for glycine. The NR2B KI mice exhibited normal locomotor activity making this ifenprodil-insensitive mouse model a valuable tool to test the specificity of NR2B selective antagonists in vivo.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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