Enantioselective effects on neurotransmission

Abstract

Methods of use, pharmaceutical formulations, and labeled versions of compounds are provided that cross the blood-brain barrier and affect the balance of excitatory versus inhibitory neurotransmission by enantioselective modulation of glutamate and GABA metabolism. In some embodiments, the glutamatergic pseudoneurotransmitter is S-2-methylglutamate (S-2MeGlu). In some embodiments, the GABAergic pseudoneurotransmitter is R-4 aminopentanomic acid (4APA) or S-4 aminopentanomic acid (S-4APA), which have high blood-brain barrier permeability and low toxicity, providing a useful pharmacological or imaging agent therein.

Description

[Background technology]

[0001] The amino acid L-glutamine and the neurotransmitters L-glutamate and gamma-aminobutyric acid (GABA) are metabolically linked via the glutamate-glutamine cycle and the GABA shunt. Imbalances in the complex metabolic interactions between excitatory (mainly glutamatergic) and inhibitory (mainly GABAergic) neurotransmission are involved in a wide range of psychiatric and neurological disorders. Genetic defects in the glutamate-glutamine cycle, either glutamine synthetase (GS) deficiency or glutaminase deficiency, result in neonatal-infant epileptic encephalopathy and early death.

[0002] Genetic defects in the GABA shunt include SSADH deficiency and GABA-transaminase deficiency, characterized by language and motor delays, cognitive impairment, ataxia, autistic behavior, hallucinations, and epilepsy in both children and adults with elevated gamma-hydroxybutyrate (GHB) and / or GABA. Widespread diseases, including mood disorders, some forms of psychosis, epilepsy, Alzheimer's disease, and Parkinson's disease, have been proposed to originate at least in part from an imbalance of excitatory and inhibitory neurotransmission. The promise of restoring balance to these opposing systems is the focus of many candidate therapeutics, some of which have progressed to widespread clinical application: receptor-specific agonists, antagonists, and allosteric regulators, transporter inhibitors, gene transfer, and most recently cell therapy.

[0003] Existing approaches fail to target the metabolic balance of the GABA shunt or the glutamate-glutamine cycle, and so far none have had a significant impact on alleviating the common psychiatric or neurodegenerative diseases listed above. Summary of the Invention

[0004] An imbalance in glutamate (excitatory) versus GABAergic (inhibitory) neurotransmission contributes to a variety of neurodevelopmental, psychiatric / behavioral, and neurodegenerative disorders. Methods of use, pharmaceutical formulations, and labeled versions of compounds are provided relating to compounds that cross the blood-brain barrier and affect the balance of excitatory versus inhibitory neurotransmission through enantioselective modulation of glutamate and GABA metabolism.

[0005] In some embodiments, compounds for use in the methods of the present disclosure are isolated enantiomers of 2-methylglutamate (2MeGlu) or 2-methylglutamine (2MeGln), which are enantioselective metabolic modulators in the GABA shunt or glutamate-glutamine cycle and have been demonstrated to have high blood-brain barrier permeability and low toxicity, providing useful pharmacological or imaging agents therein. In some embodiments, the compound of interest is (S)-2MeGlu, which is shown herein to be a glutamatergic pseudoneurotransmitter, or (S)-2MeGln, which is shown herein to be a metabolic precursor of (S)-2MeGlu.

[0006] In other embodiments, the compounds for use in the methods of the present disclosure are enantiomers of 4-aminopentanoic acid (4APA). Enantiomers of 4APA selectively displace GABA in synaptosomes, but have little or no activity on a broad panel of GABA and glutamate receptors. In some embodiments, the compounds of interest are (S)-4APA or (R)-4APA, which are shown herein to be GABAergic pseudoneurotransmitters.

[0007] In some embodiments, a composition is provided that includes an effective dose of the compounds: (S)-2MeGlu, (S)-2MeGln, (S)-4APA, (R)-4APA, and a pharma- ceutically acceptable excipient. In some embodiments, the compound in the formulation is enantiomerically pure, e.g., at least about 80%, at least about 90%, at least about 95%, at least about 99% of the selected enantiomer. In other embodiments, racemic compositions are used, e.g., racemic 2MeGln, racemic 4APA. In some embodiments, the composition is configured for delivery as a pharmacological agent. The dose may be effective for treating diseases that result in part from an imbalance in excitatory versus inhibitory neurotransmission, including epilepsy, autism, mood disorders, psychosis, Alzheimer's disease, and Parkinson's disease. In some embodiments, the disease is Parkinson's disease, and the dose may be effective for improving the patient's movement. In some embodiments, the disease is Alzheimer's disease, and the dose may be effective for improving cognitive function.

[0008] In some embodiments, a method for altering the excitatory / inhibitory balance of a neuron is provided, the method comprising administering an effective dose of one or more of (S)-2MeGlu, (S)-2MeGln, (S)-4APA, (R)-4APA, racemic 2MeGln, and racemic 4APA. In some embodiments, (S)-2MeGlu is administered. Administration of (S)-2MeGlu reduces excitatory neuronal activity by acting as a pseudoneurotransmitter and competing for glutamate in the neurotransmitter pool without significant activity at glutamate and GABA receptors. Administration of (S)-2MeGln reduces excitatory neuronal activity by acting as a metabolic precursor of (S)-2MeGlu. Administration of 4APA enantiomer reduces inhibitory neuronal activity by acting as a pseudoneurotransmitter and competing for GABA in the neurotransmitter pool without significant activity at glutamate and GABA receptors.

[0009] Acute high doses of these compounds have been shown to have minimal mortality. (R)-2MeGlu or (S)-2MeGlu cause a transient and significant decrease in response to novelty / motor activity while remaining alert and responsive to ambient noise and touch. The utility of such impaired response to novelty / motor activity has utility in the management of patients undergoing treatment or imaging sessions, as well as in the treatment of neurological and psychiatric disorders that stem in part from an imbalance in excitatory and inhibitory neurotransmission. S-2MeGlu dose-dependently rescues motor function in two different animal models of PD and cognitive improvement in an animal model of AD. R-4APA rescues motor function in a transgenic animal model of PD.

[0010] In some embodiments, an effective dose of a compound, an imaging label for positron emission tomography, e.g., 18 F, 11 C. 15 Imaging compositions are provided that include (S)-2MeGlu, (S)-2MeGln, (S)-4APA, or (R)-4APA, including O, and a pharma- ceutically acceptable excipient. In some embodiments, the composition is configured for delivery as an imaging agent.

[0011] In some embodiments, a method is provided for molecular imaging of glutamine producing and / or transporting cells, the method comprising the step of: 18 F, 11 C. 15 The method includes administering (S)-2MeGlu or 2MeGln, including 0, and detecting the presence of the imaging label by PET or other means. The primary use of PET ligands for glutamine transport is in the detection of some forms of cancer. The enantiospecific access of (S)-2MeGlu and (S)-2MeGln to the brain and metabolism makes them ideal candidates for labeling and molecular imaging of glutamine producing and / or transporting cells. [Brief description of the drawings]

[0012] The invention is best understood from the following detailed description when read in conjunction with the accompanying drawings, in which: It is emphasized that, according to common practice, the various features of the drawings are not drawn to scale. Conversely, dimensions of the various features have been arbitrarily expanded or reduced for clarity. The drawings include the following figures:

[0013] [Figure 1A] L-glutamate is involved in the GABA shunt (blue arrow) away from the Krebs cycle and in the glutamate-glutamine cycle (red arrow). Glutamate amidation proceeds primarily in astrocytes (blue font), while the reverse reaction occurs in neurons (orange font). For simplicity, the transport steps are not shown. SA and α-KG do not have exact analogs and are not shown in the diagram. Abbreviations: AKR: aldo-ketoreductase, AST: aspartate transaminase, GABA-T: GABA transaminase, GAD: glutamate decarboxylase, GHBDH: gamma-hydroxybutyrate dehydrogenase, GLDH: glutamate dehydrogenase, GLS: glutaminase, GS: glutamine synthetase, SSADH: succinic semialdehyde dehydrogenase, GABA: y-aminobutyric acid, GHB: y-hydroxybutyric acid, Gln: L-glutamine, Glu: L-glutamate, a-KG: y-ketoglutarate, SA: succinic acid, SSA: succinic semialdehyde. [Figure 1B] A hypothetical metabolic scheme of 2MeGlu to the methyl analogue of the Glu metabolite is shown. [Figure 2A] Figure 2 shows 2MeGlu in the GABA shunt metabolic pathway. Synaptosomes were incubated with 10 μM substrate at 0° C. or 37° C. and uptake was monitored over time. Error bars represent sem, n=3. [Figure 2B] FIG. 1 shows synaptosomal accumulation of 2Me analogs. Synaptosomes were incubated with 10 μM substrate at 0° C. or 37° C. and uptake was monitored over time. Error bars represent sem, n=3. [Figure 2C]Potassium-induced release of synaptosomal 2MeGlu. Synaptosomes were preincubated with 100 μM substrate for 15 min at 37° C. Pellets were washed and resuspended in normal or high potassium KRP buffer and incubated for the indicated times at 37° C. Data are presented as mean±SEM, n=3. [Figure 2D] Potassium-induced release of 4APA is shown. Synaptosomes were preincubated with 100 μM substrate for 15 min at 37° C. Pellets were washed, resuspended in normal or high potassium KRP buffer, and incubated for the indicated times at 37° C. Data are presented as mean ± SEM, n=3. [Figure 2E] Potassium-induced release of endogenous Glu and GABA is shown. Synaptosomes were preincubated. Pellets were washed and resuspended in normal or high potassium KRP buffer and incubated at 37° C. for the indicated times. Data are shown as mean±SEM, n=3. [Figure 3A] 1 shows the stereospecific conversion of 2MeGlu enantiomers by human glutamine synthetase. The reaction was carried out with 10 mM substrate and 5 ng / mL enzyme in the presence of 10 mM ATP, 20 mM MgCl2, 40 mM NH4Cl, 25 mM 2-mercaptoethanol in 100 mM imidazole, pH 7.0 buffer. [Figure 3B] 1 shows the conversion of rac-2MeGln by human glutaminase GLS1. The reaction was carried out with 10 mM substrate and 5 ng / mL enzyme in phosphate, pH 7.4 buffer. [Figure 3C] Figure 1 shows the relative concentrations of (R)- and (S)-[18O]2MeGlu produced in the GLS1 hydrolysis assay. Data are presented as mean ± SEM, n=3. [Figure 4A]Figure 1 shows the cellular metabolism of 2MeGlu and 2MeGln. Data are presented as mean ± SEM, n=3. Horizontal arrows represent the uptake-conversion-release cycle. Astrocyte uptake, amidation, and release of 2MeGlu and its amide derivative, 2MeGln, are shown. Total intracellular and extracellular amounts of 2MeGlu or [1,2-13C]Glu(-COOH) and 2MeGln or [1,2-13C]Gln(-CONH2) were determined in cells and medium. Primary astrocyte cultures were incubated for 2 h at 37°C in the presence of 1 mM racemic or enantiopure 2MeGlu or L-Glu, along with cell-free controls. [Figure 4B] Figure 1 shows the cellular metabolism of 2MeGlu and 2MeGln. Data are presented as mean ± SEM, n=3. Horizontal arrows represent the uptake-conversion-release cycle. Neuronal uptake, hydrolysis, and release of 2MeGln and its hydrolysis counterpart, 2MeGlu. Total intracellular and extracellular amounts of 2MeGln (-CONH2) and 2MeGlu (-COOH) were determined in cells and in the medium. Primary neuronal cell cultures were incubated in the presence of 1 mM 2MeGln along with a cell-free control for 2 hours at 37°C. [Figure 5A] Figure 1 shows the pharmacokinetics (column units) of 2Me compounds and their metabolites measured in mouse serum after IP injection of 100mg / kg of test compound. Concentrations are expressed per volume in serum samples and per protein content in brain samples. Data are shown as mean ± SEM, n=3. [Figure 5B] Figure 1 shows the pharmacokinetics (column units) of 2Me compounds and their metabolites measured in the brain after IP injection of 100mg / kg of test compound. Concentrations are expressed per volume in serum samples and per protein content in brain samples. Data are shown as mean ± SEM, n=3. [Figure 6A]Exploratory and locomotor behavior in 2-month-old male C57Bl / 6 mice was assessed by the total distance traveled in the novel cage test. Mice were injected and then immediately tested (acute group). Data are presented as mean ± SEM. Dose response for each of the three compounds in the novel cage test expressed as % of mice exposed to vehicle versus total distance traveled from 0 to 60 min (n = 3 mice per group). Two-way ANOVA had an interaction F(4,18) = 9.068, P = 0.0003, F dose(2,18) = 14.91, P = 0.0002, and F compound(2,18) = 21.89, P < 0.0001. Tukey's multiple comparison test showed significant differences between rac-2MeGln vs. (R)-2MeGlu (****P<0.0001) and rac-2MeGln vs. (S)-2MeGlu (***P=0.0002). [Figure 6B] Exploratory and locomotor behavior in 2-month-old male C57Bl / 6 mice was assessed by the total distance traveled in the activity chamber. Mice were injected and then immediately tested (acute group). Data are presented as mean ± SEM. The time course of activity chamber distance traveled after acute 100 mg / kg had a two-way repeated measures ANOVA with F interaction(87,580) = 1.879, P < 0.0001, F time(29,580) = 11.44, P < 0.0001, and F exposure(3,20) = 2.906, P = 0.0600 (n = 6 mice per group). Dunnett's multiple comparison test showed that several early time points were significantly different between vehicle and (R)-2MeGlu, or between vehicle and (S)-2MeGlu (*P<0.05, **P<0.01, ***P<0.001, ****P<0.0001), and vehicle was not significantly different from rac-2MeGln at any time point. [Figure 6C]Exploratory and locomotor behavior in 2-month-old male C57Bl / 6 mice was assessed by the total distance traveled in the activity chamber. Mice were injected and then immediately tested (acute group). Data are presented as mean ± SEM. The time course of activity chamber distance traveled after acute 30 mg / kg had a two-way repeated measures ANOVA with F interaction(87,580) = 0.9328, P = 0.6493, F time(29,580) = 20.13, P < 0.0001, and F exposure(3,20) = 1.805, P = 0.1786 (n = 6 mice per group). Dunnett's multiple comparison test showed that there was one time point that was significantly different between vehicle and (R)-2MeGlu (*P<0.05) or between vehicle and rac-2MeGln (#P<0.05), and vehicle was not significantly different from (S)-2MeGlu at any time point. [Figure 6D] Exploratory and locomotor behavior in 2-month-old male C57Bl / 6 mice was assessed by the total distance traveled in the activity chamber. Mice were injected and injected daily for 1 week prior to testing (chronic group). Data are presented as mean ± SEM. The time course of activity chamber distance traveled after chronic 10 mg / kg per day for 1 week had a two-way repeated measures ANOVA with F interaction (87,986) = 1.22, P = 0.0912, F time (29,986) = 62.35, P < 0.0001, and F exposure (3,34) = 1.122, P = 0.3536, (n = 6 mice per group). One vehicle group mouse and one (S)-2MeGlu group mouse were outliers using the ROUT method and were removed from the analysis. [Figure 7A] Figure 1 shows behavioral effects of chronic 10 mg / kg / day IP administration in 2-month-old male C57Bl / 6 mice in a fear conditioning test at 4 weeks of chronic exposure. Freezing by treatment group on day 2 during a 15-minute contextual memory test is shown. Data were not normally distributed. Kruskal-Wallis test had a P of approximately 0.7819. [Figure 7B]Behavioral effects of chronic 10 mg / kg / day IP administration in 2-month-old male C57Bl / 6 mice in a fear conditioning test at week 4 of chronic exposure. Freezing at baseline and during each tone presentation on day 3 is shown. Two-way repeated measures ANOVA had F interaction(9,102)=1.313, P=0.24, F tone(3,102)=13.95, P<0.0001, and F exposure(3,34)=2.015, P=0.13. All bars represent mean±SEM, n=10 mice per group. [Figure 8A] Optimization of 2MeGlu chiral separation is shown. The LC-MS / MS system was equipped with a chiral CROWNPAK CR-I(+) column. Acetonitrile was adjusted to achieve optimal resolution in the minimum time and lowest acid concentration. Final conditions: 96% acetonitrile, 0.1% trifluoroacetic acid, flow rate of 0.4 mL / min. [Figure 8B] Optimization of 2MeGlu chiral separation is shown. The LC-MS / MS system was equipped with a chiral CROWNPAK CR-I(+) column. Trifluoroacetic acid was adjusted to achieve optimal resolution in the minimum time and lowest acid concentration. Final conditions: 96% acetonitrile, 0.1% trifluoroacetic acid, flow rate of 0.4 mL / min. [Figure 8C] Optimization of 2MeGlu chiral separation is shown. The LC-MS / MS system was equipped with a chiral CROWNPAK CR-I(+) column. The mobile phase flow rate was adjusted to achieve optimal resolution in the minimum time and lowest acid concentration. Final conditions: 96% acetonitrile, 0.1% trifluoroacetic acid, flow rate of 0.4 mL / min. [Figure 9A] Synaptosomal metabolism of 2MeGlu and 4APA. Synaptosomes were preincubated with 100 μM substrate for 15 min at 37° C. Pellets were washed, resuspended in normal KRP buffer, and incubated at 37° C. while levels of potential metabolites were monitored at 5 min intervals. 4OPA and 4HPA signals were below the limit of quantification. Data are means ± SEM, n=3. [Figure 9B]Synaptosomal metabolism of 2MeGlu and 4APA. Synaptosomal metabolism and retention of 2MeGlu. Synaptosomes preincubated with 100 μM 2MeGlu were resuspended in normal KRP buffer and intra- and extra-synaptosomal levels of 2MeGlu and 2MeGln were monitored. [Figure 9C] Synaptosomal metabolism of 2MeGlu and 4APA. Total intra- and extrasynaptosomal concentrations of 2MeGlu and 2MeGln in monitored samples. Data are presented as mean±SEM, n=5. [Figure 10A] Figure 1 shows cell viability assays using 2MeGlu and 2MeGln on MCF-7, MDA-MB-231, and SK-OV-3 cancer cell lines. Compounds were tested in the range of 1 nM to 100 μM in triplicate with cisplatin as a positive control. [Figure 10B] Figure 1 shows a GLS1 inhibition assay using 2MeGlu and 2MeGln ranging from 0.5 μM to 1 mM. Data are presented as mean ± SEM, n=3. [Figure 11] Exploratory and locomotor behavior in 2-month-old male C57Bl / 6 mice was assessed by the total distance traveled in the novel cage test. Data are presented as mean ± SEM (n = 3 mice per group) of distance traveled per minute (cm) over 1-60 min post-injection. These data were used to generate the dose-response graph in Figure 6A. [Figure 12A] Figure 1 shows behavioral effects of chronic 10 mg / kg / day IP administration in 2-month-old male C57Bl / 6 mice. Elevated plus maze was performed after the first week of chronic exposure. Data are presented as mean ± SEM, n = 10 mice per group. Two-way repeated measures ANOVA for distance traveled (cm) had an F interaction (12,144) = 0.9112, P = 0.5375, F time (4,144) = 66.01, P < 0.0001, and F treatment (3,36) = 1.076, P = 0.3713. [Figure 12B]Figure 1 shows behavioral effects of chronic 10 mg / kg / day IP administration in 2-month-old male C57Bl / 6 mice. Elevated plus maze was performed after the first week of chronic exposure. Data are presented as mean ± SEM, n = 10 mice per group. One-way ANOVA on percentage of time spent in the open arms of the maze against treatment measured over 5 min had F treatment = 0.531, P = 0.664. [Figure 13] Behavioral effects of chronic 10 mg / kg / day IP administration in 2-month-old male C57Bl / 6 mice. Y-maze was performed during the second week of chronic exposure. Percent alternations over 5 min are shown as scatter plots as well as mean ± SEM, n = 10 mice per group. One-way ANOVA had F(3,36) = 2.018, P > 0.05. [Figure 14A] Figure 1 shows behavioral effects of chronic 10 mg / kg / day IP administration in 2-month-old male C57Bl / 6 mice. Morris water maze was performed during the second and third week of chronic exposure. Data are presented as scatter plots and mean ± SEM, n = 10 mice per group. Two-way repeated measures ANOVA for escape latency (sec) had F interaction (21,252) = 0.8483, P = 0.6582, F time (7,252) = 37.39, P < 0.0001, and F treatment (3,36) = 0.4551, P = 0.7153. [Figure 14B] Figure 1 shows behavioral effects of chronic 10 mg / kg / day IP administration in 2-month-old male C57Bl / 6 mice. Morris water maze was performed during the second and third week of chronic exposure. Data are presented as scatter plots and mean ± SEM, n = 10 mice per group. Two-way ANOVA for probes per quadrant (sec) had F interaction (3,36) = 0.844, P = 0.577, F quadrant (1,36) = 87.6, *** P < 0.0001, and F treatment (3,36) = 0.000, P = 1.000. [Figure 14C]Figure 1 shows behavioral effects of chronic 10 mg / kg / day IP administration in 2-month-old male C57Bl / 6 mice. Morris water maze was performed during the second and third week of chronic exposure. Data are presented as scatter plots and mean ± SEM, n=10 mice per group. One-way ANOVA of probe 1 duration (sec) in the virtual platform had P=0.3066. [Figure 15A] Figure 1 shows behavioral effects of chronic 10 mg / kg / day IP administration in 2-month-old male C57Bl / 6 mice in a fear conditioning test at 4 weeks after chronic exposure. Fear conditioning paradigm day 1, training day, all treatment groups showed equivalent learning of the tone shock association on day 1. There were no differences between experimental groups in trace learning freezing during training day, suggesting equivalent learning of the task between all experimental groups. All bars represent mean ± SEM, n = 10 mice per group. [Figure 15B] Figure 1 shows behavioral effects of chronic 10 mg / kg / day IP administration in 2-month-old male C57Bl / 6 mice in a fear conditioning test at 4 weeks after chronic exposure. Fear conditioning paradigm day 1, training day, all treatment groups showed equivalent learning of the tone shock association on day 1. There were no differences between experimental groups in freezing during the intertrial interval (ITI) during training day, suggesting equivalent learning of the task between all experimental groups. All bars represent mean ± SEM, n = 10 mice per group. [Figure 16A] Behavioral effects of chronic 10 mg / kg / day IP administration in 2-month-old male C57Bl / 6 mice in a fear conditioning test at week 4 after chronic exposure. Fear conditioning paradigm day 3, cued recall: As shown in FIG. 7B, no significant differences were detected in freezing on day 3 between experimental groups across the three tone presentations. In addition, no significant differences were observed during the 18-s tracing period following the three tone presentations on day 3. All bars represent mean ± SEM, n=10 mice per group. [Figure 16B]Behavioral effects of chronic 10 mg / kg / day IP administration in 2-month-old male C57Bl / 6 mice in a fear conditioning test at week 4 after chronic exposure. Fear conditioning paradigm day 3, cued recall: As shown in FIG. 7B, no significant differences in freezing were detected between experimental groups on day 3 across the three tone presentations. Finally, no significant differences in freezing were detected between experimental groups during the intertrial interval (ITI) on day 3 after tone presentation, indicating comparable cue recall between experimental groups on day 3. All bars represent mean ± SEM, n=10 mice per group. [Figure 17] Study design: Enantiomers of 4-aminopentanoic acid (4APA) were first evaluated for mouse brain synaptosomal uptake, GABA displacement, and release after membrane depolarization with high potassium cation concentrations (left). They were then injected into mouse brains to assess pharmacokinetics and effects on mouse behavior (right). [Figure 18] Time- and temperature-dependent uptake of 4APA into mouse brain synaptosomes at 4° C. (dashed line) and 30° C. (solid line). The y-axis represents synaptosomal concentration of 4APA (nmol / mg protein) measured after incubation with 10 μM (R)-4APA, (S)-4APA or rac-4APA for up to 30 min at 37° C. or 4° C. (n=3 samples per group). Two-way ANOVA was significant for compound / temperature (P<0.0001), time (P<0.0001), and the interaction (P<0.0001). Tukey's multiple comparison test had P<0.0001 for concentrations at 37°C versus 4°C for each compound, and synaptosomal concentrations at 37°C were significantly different for (R)-4APA versus (S)-4APA (****P<0.0001), (R)-4APA versus rac-4APA (++++P<0.0001), and (S)-4APA versus rac-4APA (^^^^P<0.0001). [Figure 19]Figure 1 shows the effect of 4APA enantiomers on endogenous GABA in mouse brain synaptosomes. After incubation with (R)-4APA, (S)-4APA, or rac-4APA (100 μM) or vehicle for 15 min at 37°C, followed by incubation with 5 mM K+ or 40 mM K+ for 15 min at 37°C, synaptosomal concentrations of GABA and 4APA (nmol / mg protein) were measured (n=3 samples per group). GABA concentrations: Two-way ANOVA was significant for exposure (P<0.0001), low vs. high K+ concentration (P<0.0001), and the interaction (P<0.01). Sidak's multiple comparison test had ****P<0.0001 for GABA concentrations for each compound vs. vehicle, and ++++P<0.0001 or +P<0.05 for GABA concentrations at low vs. high K+ concentrations for each compound or vehicle. 4APA concentration: Two-way ANOVA was significant for exposure (P<0.0001), low vs. high K+ concentrations (P<0.0001), and the interaction (P<0.05). Sidak's multiple comparison test had ****P<0.0001 or **P<0.01 for 4APA concentrations for each compound vs. vehicle, and +++P<0.001 or ++P<0.01 for 4APA concentrations at low vs. high K+ concentrations for each compound or vehicle. [Figure 20A]Figure 1 shows the pharmacokinetics of 4APA compound measured in serum and brain after a single IP injection of 100 mg / kg in 2-3 month old male C57Bl / 6 mice (n=3 mice per group). Concentrations are expressed as μmol / L in serum samples (solid line) and pmol / mg protein in brain samples (dashed line). Results are plotted for each measurement. In brain, two-way ANOVA for repeated measures was significant for 4APA enantiomer (P<0.001) and time (P<0.01), and Sidak's multiple comparison test was significant only at 0.5 vs. 4 h for (S)-4APA (+P<0.05). In serum, repeated measures two-way ANOVA was significant for time (P<0.0001) and the interaction (P<0.01), and for both enantiomers, Sidak's multiple comparison test was significant only at the first time point, whereas at all other time points, it was significant at 0.5 vs. 4 hours for S-4APA (***P<0.001). [Figure 20B] Figure 1 shows the pharmacokinetics of 4APA compound measured in serum and brain after a single IP injection of 100 mg / kg into 2-3 month old male C57Bl / 6 mice (n=3 mice per group). Cmax, Tmax, and T1 / 2 values ​​(mean ± SEM) are presented for each enantiomer in serum and brain, and there were no significant differences between the two enantiomers in any of these three pharmacokinetic measurements. [Figure 21A] Exploratory and locomotor behavior was assessed in 2-month-old male C57Bl / 6 mice in a novel cage test immediately following a single injection of compound or vehicle (n=3 mice per group). Dose-response relationship for (R)-4APA and (S)-4APA for total distance traveled over 30 min post-injection. Time course of distance traveled over the first 10 min. Two-way ANOVA had F interaction P=0.40, F dose P<0.0001, and F enantiomer P=0.38. [Figure 21B]Exploratory and locomotor behavior was assessed in 2-month-old male C57Bl / 6 mice in a novel cage test immediately following a single injection of compound or vehicle (n=3 mice per group) for distance traveled over the first 10 min after injection. Two-way repeated measures ANOVA had F interaction P<0.0001, F time P<0.0001, and F exposure P=0.0001. Tukey's multiple comparison test had all concentrations of both enantiomers significantly different from vehicle at 1-4 min (**P<0.01), at 5-7 and 9 min, 300 mg / kg (R)-4APA and both enantiomers at 900 mg / kg were significantly different from vehicle (++P<0.01), and at 10 min, only the two higher doses of (R)-4APA were significantly different from vehicle (*P<0.05). The R and S enantiomers at the same dose were not significantly different from each other. [Figure 22] Nine-week-old male C57Bl / 6 mice (n=14 per group) were treated with vehicle, 5 or 50 mg / kg / day S-2MeGlu or R-4APA IP on days -5 to 14, and vehicle or 40 mg / kg / day MPTP IP on days 1 and 2. Higher overall kinematic scores indicate greater impairment of gait and balance. ANOVA had P<0.01 and Sidak's multiple comparison test was performed v.Veh / Veh for each group (*P<0.05, **P<0.01, NS had P=0.32). [Figure 23] Eight-week-old male Line 61 mice (n=14 per group) were treated with vehicle, 5 or 50 mg / kg / d S-2MeGlu or R-4APA IP on days 1-7 and then tested for motor function using the tapered beam test. Mice were classified into those that completed the task within 120 seconds, those that fell off the beam, or those that took more than 120 seconds. Chi-square test had P<0.005. [Figure 24]Percent alternation in the Y-maze for wild-type (WT) or line 41 transgenic mice treated with vehicle or 10 mg / kg IP S-2MeGlu (n=14 4-month-old males per group) is shown. WT / Veh was significantly different from random (50%) alternation (**P<0.01), whereas line 41 / veh was not significantly different from random, indicating impaired working memory in transgenic mice. Both groups treated with S-2MeGlu had percent alternation significantly different from random (*P<0.05). [Diagram 25] Figure 25 shows the efficacy of 2MeGlu, 2MeGln, and 4APA to prevent neurodegeneration. Mouse hippocampal slice cultures were exposed to kanic acid (KA) to induce dose-dependent neurodegeneration as determined by propridium iodide staining. Slice cultures were incubated with 5 or 50 micromolar racemic (rac) 2MeGlu, 2MeGln, or 4APA. At lower doses of KA, higher doses of 2MeGlu or 2MeGln (50 μM) substantially reduced neurodegeneration by about 50% (Figure 25). Neither dose of 2MeGlu or 2MeGln was neuroprotective at higher doses of KA. 4APA was not neuroprotective in this model at either 5 or 50 μM (not shown in Figure 25). [Figure 26] Four adult mice (M1-M4) were injected with radiolabeled 2MeGlu, either with 2.5 mg of non-radioactive 2MeGlu (M1) or without a cold spike (M2-M4), and then imaged by PET. 11C-2MeGlu showed a rapid rise in brain radioactivity (3% ID / g), most of which was cleared within the first 10 min, likely associated with labeled compound in the blood. Longer time points showed greater apparent brain retention in non-spiked injections, with approximately 0.5% of the injected dose retained throughout the brain for up to 40 min after injection. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Before the present methods and compositions are described, it is to be understood that this invention is not limited to the particular methods or compositions described, as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting, since the scope of the present invention will be limited only by the appended claims.

[0015] Where a range of values ​​is provided, it is understood that each intervening value between the upper and lower limits of that range is also specifically disclosed to the tenth of the unit of the lower limit, unless the context clearly dictates otherwise. Each smaller range between any stated value or intervening value within a stated range and any other stated value or intervening value within that stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may be independently included or excluded in the range, and each range in which either, neither, or both limits are included in the smaller range is also encompassed within the invention, subject to any specifically excluded limits in the stated range. Where a stated range includes one or both of the limits, ranges excluding either or both of those included limits are likewise included in the invention.

[0016] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, some potential and preferred methods and materials are described herein. All publications mentioned herein are incorporated by reference to disclose and describe the methods and / or materials in connection with which the publications are cited. In case of conflict, it should be understood that the present disclosure supersedes any disclosure of the incorporated publication.

[0017] It should be noted that as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a cell" includes a plurality of such cells, and reference to "the peptide" includes reference to one or more peptides and equivalents thereof known to those skilled in the art, such as polypeptides.

[0018] The publications discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein should be construed as an admission that the present invention is not entitled to antedate such publications by virtue of prior invention. Further, the dates of publication provided may be different from the actual publication dates which may need to be independently confirmed.

[0019] The terms "subject," "individual," and "patient" are used interchangeably herein to refer to a mammal being evaluated for and / or treated for therapy. In some embodiments, the mammal is a human. The terms "subject," "individual," and "patient" include, but are not limited to, individuals with a disease. Subjects may be humans, but also include other mammals, particularly mammals useful as laboratory models for human disease, e.g., mice, rats, and the like.

[0020] The term "diagnosis" is used herein to refer to the identification of a molecular or pathological state, disease or condition in a subject, individual or patient.

[0021] The term "prognosis" is used herein to refer to the prediction of the likelihood of death or disease progression, including recurrence, spread, and drug resistance, in a subject, individual, or patient. The term "prediction" is used herein to refer to the act of foretelling or estimating, based on observation, experience, or scientific reasoning, the likelihood that a subject, individual, or patient will experience a particular event or clinical outcome. In one example, a physician may attempt to predict the likelihood that a patient will survive.

[0022] As used herein, the terms "treatment", "treating" and the like refer to the administration of an agent or the performance of a procedure to or in a subject, individual, or patient for the purpose of obtaining an effect. The effect may be prophylactic, in that it completely or partially prevents a disease or its symptoms, and / or may be therapeutic, in that it provides a partial or complete cure for a disease and / or symptoms of a disease. As used herein, "treatment" may include the treatment of neurological diseases in mammals, particularly humans, and includes (a) inhibiting the disease, i.e., arresting its onset, and (b) alleviating the disease or its symptoms, i.e., causing regression of the disease or its symptoms.

[0023] Treating can refer to any indication of successful treatment or amelioration or prevention of a disease, including any objective or subjective parameter, such as alleviation, remission, or reduction of symptoms, or making the disease state more tolerable to the patient, slowing the rate of degeneration or decline, or making the end point of degeneration less debilitating. The treatment or amelioration of symptoms can be based on objective or subjective parameters, including the results of an examination by a physician. Thus, the term "treating" includes administering an agent to prevent or delay, alleviate, or arrest or inhibit the onset of symptoms or conditions associated with a disease or other disease. The term "therapeutic effect" refers to the reduction, elimination, or prevention of a disease, a symptom of a disease, or a side effect of a disease in a subject.

[0024] As used herein, the term "dosing regimen" refers to a series of unit doses (typically two or more) administered to a subject individually, typically separated by a period of time. In some embodiments, a given therapeutic agent has a recommended dosing regimen, which may include one or more doses. In some embodiments, the dosing regimen includes multiple doses, each dose separated from the other by a period of equal length, and in some embodiments, the dosing regimen includes multiple doses, with at least two different periods of time separating the individual doses. In some embodiments, all doses within the dosing regimen are the same unit dose amount. In some embodiments, different doses within the dosing regimen are different amounts. In some embodiments, the dosing regimen includes a first dose amount, followed by one or more additional doses in a second dose amount that is different from the first dose amount. In some embodiments, the dosing regimen includes a first dose amount, followed by one or more additional doses in a second dose amount that is the same as the first dose amount. In some embodiments, the dosing regimen correlates with a desired or beneficial outcome when administered across a relevant population (i.e., is a therapeutic dosing regimen).

[0025] "In combination with," "combination therapy," and "combination product" refer, in certain embodiments, to the simultaneous administration of an agent described herein to a patient in combination with an additional therapy, e.g., surgery, treatment with other compounds, etc. When administered in combination, each component can be administered simultaneously or sequentially in any order at different times. Thus, each component can be administered separately but sufficiently close in time to provide the desired therapeutic effect.

[0026] "Concomitant administration" refers to administration of one or more components, such as active agents, at a time such that the combination has a therapeutic effect. Such concomitant administration may involve co-administration (i.e., at the same time), prior administration, or subsequent administration of the components. Those skilled in the art will have no difficulty in determining the appropriate timing, sequence, and dosages of administration.

[0027] The use of the term "in combination" does not restrict the order in which prophylactic and / or therapeutic agents are administered to a subject with a disorder. A first prophylactic or therapeutic agent can be administered prior to (e.g., 5 minutes, 15 minutes, 30 minutes, 45 minutes, 1 hour, 2 hours, 4 hours, 6 hours, 12 hours, 24 hours, 48 ​​hours, 72 hours, 96 hours, 1 week, 2 weeks, 3 weeks, 4 weeks, 5 weeks, 6 weeks, 8 weeks, or 12 weeks before), simultaneously with, or subsequent to (e.g., 5 minutes, 15 minutes, 30 minutes, 45 minutes, 1 hour, 2 hours, 4 hours, 6 hours, 12 hours, 24 hours, 48 ​​hours, 72 hours, 96 hours, 1 week, 2 weeks, 3 weeks, 4 weeks, 5 weeks, 6 weeks, 8 weeks, or 12 weeks after) the administration of a second prophylactic or therapeutic agent to a subject with a disorder.

[0028] The term "sample" with respect to a patient includes CSF, blood, and other liquid samples of biological origin, solid tissue samples such as biopsy specimens or tissue cultures or cells derived therefrom, and the progeny thereof. The term also includes samples that have been manipulated in any way after procurement, such as by treatment with reagents, washing, or enrichment for specific cell populations such as diseased cells. This definition also includes samples enriched for specific types of molecules, e.g., nucleic acids, polypeptides, and the like. The term "biological sample" encompasses clinical samples, including tissue obtained by surgical resection, tissue obtained by biopsy, cells in culture, cell supernatants, cell lysates, tissue samples, organs, bone marrow, blood, plasma, serum, and the like. "Biological sample" includes samples obtained from diseased cells of a patient, e.g., samples containing polynucleotides and / or polypeptides obtained from diseased cells of a patient (e.g., cell lysates or other cell extracts containing polynucleotides and / or polypeptides), as well as samples containing diseased cells from a patient. Biological samples containing diseased cells from a patient may also contain non-disease cells.

[0029] The terms "specific binding," "specifically binds," and the like refer to the preferential non-covalent or covalent binding of a molecule relative to other molecules or moieties in a solution or reaction mixture (e.g., an antibody specifically binds to a particular polypeptide or epitope relative to other available polypeptides). In some embodiments, the affinity of one molecule for which it specifically binds to another molecule is greater than or equal to 10 -5 M or less (e.g., 10 -6 M or less, 10 -7 M or less, 10 -8 M or less, 10 -9 M or less, 10 -10 M or less, 10 -11 M or less, 10 -12 M or less, 10 -13 M or less, 10 -14 M or less, 10 -15 M or less, or 10 -16 The affinity of a given molecule is characterized by a KD (dissociation constant) of 0.01 M or less. "Affinity" refers to the strength of binding, with increased binding affinity being correlated with a lower Kd.

[0030] compound Neurotransmitters are signaling molecules secreted by neurons to affect another cell across a synapse. The cell that receives the signal, any major body part, or target cell, may be another neuron, but also a gland or muscle cell. Neurotransmitters are released from synaptic vesicles into the synaptic cleft, where they can interact with neurotransmitter receptors on the target cell. The effect of a neurotransmitter on a target cell is determined by the receptor to which it binds. Multiple neurotransmitters are synthesized from simple precursors, such as amino acids, that are readily available and often require few biosynthetic steps for conversion.

[0031] Neurotransmitters can have excitatory, inhibitory, or modulatory effects on target cells. This effect is determined by the receptors with which the neurotransmitter interacts with the postsynaptic membrane. Neurotransmitters can affect the flow of transmembrane ions and increase (excitatory) or decrease (inhibitory) the probability that a contacting cell will generate an action potential.

[0032] A pseudoneurotransmitter is a compound that is not the normal neurotransmitter of a neuron, but can be taken up by a neuron, stored in its vesicles, and released together with the normal neurotransmitter of a neuron when the neuron is stimulated.A pseudoneurotransmitter can have therapeutic value for its ability to compete with normal neurotransmitters for synaptic release without acting on the receptors activated by normal neurotransmitters.In some embodiments, a pseudoneurotransmitter substantially reduces the activation of the cognate receptor for the neurotransmitter, for example, has less than 50% activation, less than 25% activation, less than 10% activation, less than 5% activation, less than 1% activation, or even less activation, compared to normal neurotransmitters, i.e., glutamate or GABA.

[0033] Fluorescent pseudoneurotransmitters are of interest for imaging purposes and can serve as substrates for synaptic vesicle transporters: these optical tracers allow visualization of the uptake and release of neurotransmitters from synaptic terminals.

[0034] Glutamatergic neurons use glutamate, one of the most common excitatory neurotransmitters in the central nervous system (CNS). Glutamate receptors are present on presynaptic and postsynaptic neurons, as well as on glial cells. These include both ionotropic (NMDA, AMPA / KA) and metabotropic (mGluR) receptors. The effects of Glu are determined by the receptor subtype, localization (synaptic, perisynaptic, and extrasynaptic) in the postsynaptic density, and interactions with various scaffolding and signaling proteins (not shown). Glu receptor stimulation leads not only to rapid ionotropic effects, but also to synaptic plasticity, e.g., long-term potentiation (LTP) and long-term depression (LTD) via cognate signaling cascades. Excitotoxicity is involved in certain chronic diseases, including ischemic stroke, epilepsy, amyotrophic lateral sclerosis, Alzheimer's disease, Huntington's disease, and Parkinson's disease.

[0035] Enantiomerically pure compositions are provided from 2MeGlu, including (S)-2-MeGlu. (S)-2-MeGlu is not a substrate for GAD or GLDH and does not proceed through the GABA shunt or oxidative deamination. The S enantiomer (the L isomer, by convention used for natural amino acids) is shown herein to be avidly transported to synaptosomes and stored and released like L-Glu. Although a substitute for L-Glu in the neurotransmitter pool, (S)-2MeGlu does not have significant activity across a broad range of glutamate and GABA receptors and is therefore a pseudoneurotransmitter. Only the (S)-2MeGlu enantiomer is a substrate for glutamine synthase, thereby allowing it to enter the glutamate-glutamine cycle, but (S)-2MeGlu is not an efficient substrate for the reverse reaction. The net effect in vivo is that the pseudoneurotransmitter (S)-2MeGlu rapidly accumulates in the brain as (S)-2MeGln, which then slowly converts back to (S)-2MeGlu. Exposure to rac-2MeGln results in an equivalent but more rapid appearance of 2MeGln in the brain, with a slow generation of 2MeGlu over time. (S)-2MeGlu or rac-2MeGln are used in the disclosed methods as pharmacological agents to alter the excitatory / inhibitory balance in the brain. Specifically, (S)-2-MeGlu dose-dependently rescues motor function in a model of PD. (S)-2MeGlu also improves cognitive improvement in a mouse model of AD. (S)-2MeGlu or (S)-2MeGln each suppresses neurodegeneration in mouse hippocampal slice cultures. In another embodiment, (S)-2MeGlu or rac-2MeGln is used as an imaging agent for GS-expressing or Gln-transporting cells.

[0036] GABA (gamma-aminobutyric acid) is used in the majority of fast inhibitory synapses in virtually all parts of the brain. GABA is formed from glutamate by the addition of glutamic acid decarboxylase and vitamin B6. Once GABA is formed, it is released into the postsynaptic terminal of the neuron. GABA receptors are the receptors that respond when GABA is released into the postsynaptic nerve terminal. These are considered the main inhibitory receptors for the central nervous system. GABA receptors are subdivided into GABAa and GABAb. GABAa is classified as a ligand-gated ion channel / inotropic receptor. GABAa is considered in fast synaptic inhibition. When GABA binds to the receptor, an ion pore opens, allowing chloride to move through the cell membrane. Chloride is a negatively charged ion that follows areas of positive charge. Typically, chloride flows into the intracellular space. The addition of a negative charge lowers the resting potential of the cell, thus causing an inhibitory effect. GABAa receptors are located throughout the central nervous system. However, they are highly concentrated in the limbic system and retina. GABAb receptors are G-coupled protein receptors. GABAb receptors are considered slow synaptic inhibitors. After GABA binds to the receptor, potassium conductance increases. Adenylyl cyclase is activated, preventing calcium entry and thus inhibiting presynaptic release of other neurotransmitters. Locations of GABAb include the thalamic pathway and the cerebral cortex.

[0037] Pseudoneurotransmitters and imaging agents for GABAergic neurons include enantiomers of 4-aminopentanoic acid (4APA). Enantiomers of 4APA selectively replace GABA in synaptosomes, but have little or no activity on a broad panel of GABA and glutamate receptors. In some embodiments, the compound of interest is (S)-4APA or (R)-4APA, which are herein shown to be GABAergic pseudoneurotransmitters. R-4APA has been shown to rescue motor function in models for PD.

[0038] The compound of the present disclosure, or its pharma- ceutically acceptable salt, has one or more stereocenters that can be separated to utilize individual enantiomers and / or diastereomers.Methods for generating individual diastereomers and / or enantiomers are known in the art, and include, but are not limited to, chiral chromatography, for example, supercritical fluid chromatography on a chiral amylose column, using organometallic addition to chiral auxiliary groups, for example, chiral sulfinimines, and chromatography such as diastereoselective and / or enantioselective synthesis.See, for example, the procedures described in Examples 1 and 2. In some embodiments, the compound is enantiomerically enriched and is present in an enantiomeric excess (ee) of about 90% to about 99.999%, for example, about 90% to about 99.99%, about 93% to about 99.99%, about 95% to about 99.9%, about 95% to about 99.9%, about 97% to about 99.9%, about 98% to about 99.9%, or about 99% to about 99.99% ee. Unless otherwise indicated, the predominant isomer is the stereochemistry shown in the compound structures herein. In some embodiments, the compound is predominantly the R isomer. In some embodiments, the compound is predominantly the S isomer.

[0039] Compounds, such as pseudoneurotransmitters, including but not limited to (S)-2-MeGlu or (R)-4APA, can be formulated with pharmaceutically acceptable carriers (one or more organic or inorganic components, natural or synthetic, with which the subject agent is combined to facilitate its application). Suitable carriers include sterile saline, but other aqueous and non-aqueous isotonic sterile solutions and suspensions known to be pharmaceutically acceptable are known to those skilled in the art. An "effective amount" refers to an amount that can ameliorate or slow the progression of a disease, degenerative or damaging condition. An effective amount can be determined on an individual basis, and is based in part on a consideration of the condition being treated and the results desired. An effective amount can be determined by those skilled in the art utilizing such factors and using no more than routine experimentation.

[0040] As used herein, a "therapeutically effective amount" refers to that amount of a therapeutic agent sufficient to treat or manage a disease or disorder. A therapeutically effective amount can refer to an amount of a therapeutic agent sufficient to delay or minimize the onset of a disease, for example, to delay or minimize a neurological disorder. A therapeutically effective amount can also refer to an amount of a therapeutic agent that provides a therapeutic benefit in the treatment or management of a disease. Additionally, a therapeutically effective amount with respect to a therapeutic agent of the present invention means an amount of a therapeutic agent alone or in combination with other therapies that provides a therapeutic benefit in the treatment or management of a disease.

[0041] Typically, the dosage of drug in the formulation will be from about 0.1 mg of drug per kg of subject body weight per day up to about 1000 mg / kg / day, e.g., 0.5 mg / kg / day, 1 mg / kg / day, 5 mg / kg / day, 10 mg / kg / day, 20 mg / kg / day, 50 mg / kg / day, 75 mg / kg / day, 100 mg / kg / day, 200 mg / kg / day, 250 mg / kg / day, 500 mg / kg / day, 750 mg / kg / day, up to about 100 mg / kg / day, or more.

[0042] Doses in the range of 0.01 to 1 mg per kg of patient body weight may be utilized for intrathecally administered radionuclide therapeutic compositions. Larger doses in the range of 0.1 to 10 mg per kg of patient body weight may be used for imaging agents having relatively non-toxic imaging moieties. The amount utilized will depend on the sensitivity of the imaging method and the relative toxicity of the imaging moiety.

[0043] For imaging or therapeutic use, dosage and frequency may vary depending on the half-life of the drug in the patient. Those skilled in the art will understand that such guidelines are adjusted for the molecular weight of the active agent, clearance from blood, mode of administration, and other pharmacokinetic parameters. Dosage may also vary by local administration, e.g., intranasal, inhalation, etc., or systemic administration, e.g., im, ip, iv, oral, etc.

[0044] The active agent can be administered by any suitable means, including topically, orally, parenterally, intrapulmonary, and intranasally. Parenteral infusion includes intramuscular, intravenous (bolus or slow drip), intraarterial, intraperitoneal, intrathecal, or subcutaneous administration. The agent can be administered in any manner that is medically acceptable. This may include injection by parenteral routes such as intravenous, intravascular, intraarterial, subcutaneous, intramuscular, intratumoral, intraperitoneal, intraventricular, intradural, or other, and oral, nasal, ocular, rectal, or topical. Sustained release administration is also specifically included in the present disclosure, by means such as depot injection or erodible implants.

[0045] Salts include, but are not limited to, Na, K, Ca, Mg, ammonium, tetraalkylammonium, aryl and alkylsulfonates, phosphates, carboxylates, sulfates, Cl, Br, and guanidinium.

[0046] Unless otherwise specified, a reference to an atom is meant to include isotopes of that atom. For example, a reference to H is 1 H, 2 H (i.e., D), and 3 H (i.e., T) and reference to C 12 C and all isotopes of carbon ( 13 C, etc.) are included.

[0047] Salts, solvates, hydrates, and prodrug forms of the compounds are also of interest.Polymorphic, pseudopolymorphic, amorphous, and co-crystalline forms of the compounds are also of interest.All such forms are encompassed by the present disclosure.Thus, the compounds described herein include their salts, solvates, hydrates, prodrugs, enantiomeric, and isomeric forms, including their pharma-ceutically acceptable salts, solvates, hydrates, prodrugs, and isomers.

[0048] Target condition for treatment The metabolism of glutamate, the main excitatory neurotransmitter and precursor of GABA, is highly complex and compartmentalized in the brain. Maintenance of these neurotransmitter pools depends on de novo synthesis of glutamine in astrocytes, which requires both the anaplerotic enzymes pyruvate carboxylase and glutamine synthetase. Glutamate is formed directly from glutamine by deamidation via phosphate-activated glutaminase, a reaction that also results in ammonia. Glutamate plays a key role linking carbohydrate and amino acid metabolism via the tricarboxylic acid (TCA) cycle, as well as in nitrogen transport and ammonia homeostasis in the brain. Both glutamate and GABA play dual roles in the brain as metabolites and important neurotransmitters mediating excitatory and inhibitory signals, respectively, so their metabolic pathways are of considerable interest. The direct precursor for the neuronal synthesis of glutamate is glutamine. This reaction is catalyzed by phosphate-activated glutaminase (PAG), which hydrolytically deamidates glutamine to form glutamate and ammonia. The enzyme that converts glutamate to glutamine, glutamine synthetase (GS), is localized in astrocytes.

[0049] The compounds of the invention affect the balance between excitatory (glutamate-mediated) and inhibitory (GABA-mediated) neurotransmission by competing for glutamate or GABA pools without activating the receptors.

[0050] Neurodegenerative disorders included in the methods of the present disclosure include Parkinson's disease, including neurological disorders that share similar symptoms to those seen in Parkinson's disease-related disorders. In some cases, neurological disorders may exhibit symptoms similar to Parkinson's disease, atypical Parkinson's disease, or Parkinson-plus disease. Examples include, but are not limited to, drug-induced parkinsonism, progressive supranuclear palsy, vascular parkinsonism, dementia with Lewy bodies, diffuse Lewy body disease, corticobasal degeneration, multiple system degeneration (Shy-Drager syndrome), Alzheimer's disease, Pick's disease, frontotemporal dementia, multiple system atrophy, vascular dementia, and progressive supranuclear palsy (Steel-Richardson syndrome). Other conditions that are also included in the method of the present invention include vascular dementia, diffuse white matter disease (Binswanger's disease), dementia of endocrine or metabolic origin, dementia of head trauma and diffuse brain damage, dementia pugilistica and frontal lobe dementia, age-related dementia and other dementias, and conditions with memory loss.In some cases, neurological disorders may not respond well to dopaminergic treatment and may be caused as a result of various vascular, drug-related, infectious, toxic, structural and other known secondary causes.Drug-induced parkinsonism may be caused by antipsychotics and antiemetics, as well as drugs that block postsynaptic dopamine D2 receptors with high affinity, such as sodium valproate, antidepressants, reserpine, tetrabenazine, etc.

[0051] Parkinson's disease is a slowly progressive degenerative disorder characterized by resting tremor, stiffness (rigidity), slow and reduced movement (bradykinesia), and eventually gait and / or postural instability. Diagnosis is clinical. Conventional treatment aims to restore dopaminergic function in the brain with levodopa + carbidopa and / or other drugs, such as dopamine agonists, monoamine oxidase type B [MAO-B] inhibitors, amantadine. In cases of refractory disabling symptoms in patients without dementia, stereotactic deep brain stimulation or lesion surgery, as well as levodopa and apomorphine pumps, may be helpful.

[0052] The pathological hallmark of Parkinson's disease is Lewy bodies filled with synuclein in the nigrostriatal system, but synuclein can accumulate in many other parts of the nervous system, including the dorsal motor nucleus of the vagus nerve, the basal nucleus of Meynert, the hypothalamus, the neocortex, the olfactory bulb, the sympathetic ganglia, and the myenteric plexus of the gastrointestinal tract. Lewy bodies appear in a temporal sequence, and many experts believe that Parkinson's disease is a relatively late-onset systemic synucleinopathies. Other synucleinopathies (synuclein deposition disorders) include Lewy bodies and multiple system atrophy. Parkinson's disease may share features of other synucleinopathies, such as autonomic dysfunction and dementia.

[0053] In Parkinson's disease, pigmented neurons in the substantia nigra, locus ceruleus, and other brainstem dopaminergic cell groups degenerate. Loss of substantia nigra neurons leads to dopamine depletion in the dorsal aspect of the nucleus basalis (part of the basal ganglia), causing many of the motor symptoms of Parkinson's disease.

[0054] A genetic predisposition may be present in at least some cases of Parkinson's disease. Approximately 10% of patients have a family history of Parkinson's disease. Several abnormal genes have been identified. The inheritance is autosomal dominant for some genes and autosomal recessive for others. Mutations in leucine-rich repeat kinase 2 (LRRK2) are one of the most common mutations in Parkinson's disease patients, and it is the most common autosomal dominant mutation in the genetic form of the disease.

[0055] The diagnosis of Parkinson's disease is clinical. Parkinson's disease is suspected in patients with characteristic unilateral resting tremor, reduced movement, or rigidity. During finger-nose coordination testing, tremor is absent (or attenuated) in the limb being tested. During neurological examination, patients are unable to perform rapid alternating or rapid successive movements. Sensation and strength are usually normal. Reflexes are normal but may be difficult to elicit because of prominent tremor or rigidity. Slowness and reduced movement due to Parkinson's disease must be differentiated from reduced movement and spasticity due to lesions of the corticospinal tract. To help distinguish Parkinson's disease from secondary or atypical parkinsonism, clinicians often test responsiveness to levodopa. A large and sustained response strongly supports Parkinson's disease.

[0056] Levodopa is currently the most effective treatment. However, when Parkinson's disease is progressing, sometimes soon after diagnosis, the response to levodopa is complex and can cause fluctuations in motor symptoms and dyskinesias. To reduce the time levodopa is taken and therefore minimize these effects, clinicians can consider treating younger patients with mild impairment with MAO-B inhibitors (selegiline, rasagiline), dopamine agonists (e.g., pramipexole, ropinirole, rotigotine), and amantadine (which is also the best option when trying to reduce peak-dose dyskinesias). However, if these drugs do not adequately control symptoms, clinicians should promptly initiate levodopa, as it can usually improve quality of life significantly. Currently, evidence suggests that levodopa becomes ineffective due to disease progression, not cumulative exposure to levodopa.

[0057] Deep brain stimulation of the subthalamic nucleus or globus pallidus interna is often recommended for patients with levodopa-induced dyskinesia or significant motor fluctuations, and this treatment can regulate the overactivity of the basal ganglia and thus reduce Parkinson's symptoms in patients with Parkinson's disease.Stimulation of the ventral intermediate nucleus of the thalamus may be recommended only for patients with tremor, but most patients also have other symptoms, so stimulation of the subthalamic nucleus, which relieves tremor and other symptoms, is usually preferred.If the main problem is poor control of dyskinesia or if the patient is at increased risk of cognitive decline, the globus pallidus interna is a good target.

[0058] Suitable subjects include any subject who exhibits symptoms of Parkinson's disease, such as bradykinesia, repetitive movements, tremors, limb rigidity, gait and balance problems, inability to aim due to weakness of eye muscles, weakness, loss of sensation, non-motor symptoms such as REM sleep behavior disorder, neuropsychiatric symptoms including mood disorders and cognitive changes, anxiety, lethargy, changes in thinking ability, attention or vigilance level and visual hallucinations, intellectual and functional deterioration, forgetfulness, personality changes, autonomic dysfunction affecting cardiovascular, respiratory, urinary, gastrointestinal and sweat promotion functions, difficulty breathing and swallowing, inability to sweat, orthostatic hypotension, pain, constipation and loss of smell, such as hyposmia. In some embodiments, the subject may experience significant speech or language disorder, significant frontal lobe presentation and freezing of gait. The method of the present invention improves one or more disease indicators, including in particular movement disorders.

[0059] In some embodiments, the subject may not exhibit any obvious symptoms of Parkinson's disease. In some cases, the subject in need may exhibit increased susceptibility to infections, hypothermia, weak bones, joint stiffness, arthritis, hunched posture, slow movement, overall decreased energy, constipation, urinary incontinence, memory loss, slow thinking, slow reflexes, balance difficulties, decreased vision, decreased peripheral vision, hearing loss, wrinkled skin, gray hair, weight loss, loss of muscle tissue.

[0060] In some embodiments, the subject is selected from subjects diagnosed with Alzheimer's disease. In a clinical sense, an effective amount is an amount of drug that, when administered for a suitable period of time, usually at least about 1 week, and sometimes up to about 2 weeks or more, about 4 weeks, 8 weeks, 12 weeks or more, shows a change in symptoms of cognitive impairment in individuals with Alzheimer's disease compared to healthy individuals. For example, an effective dose is a dose that, when administered for a suitable period of time, slows or stops cognitive decline, e.g., by about 20% or more, e.g., 30% or more, 40% or more, or 50% or more, and in some cases, 60% or more, 70% or more, 80% or more, or 90% or more, i.e., stabilizes cognitive performance. In some embodiments, an effective amount or dose can not only slow or stop the progression of a disease state, but can also induce a reversal of the condition. For example, an effective dose may improve cognition in individuals with Alzheimer's disease by, for example, 1.5-fold, 2-fold, 3-fold, 4-fold, 5-fold, and in some instances, 6-fold, 7-fold, 8-fold, 9-fold, or 10-fold or more.

[0061] The method for measuring cognition or vision is also well known in the art, and any of them can be used to determine effective dose.Examples include cognitive tests and tests such as IQ tests for measuring cognitive ability, such as attention and concentration, ability to learn complex tasks and concepts, memory, information processing, visual-spatial function, ability to generate and understand language, ability to solve problems and make decisions, and ability to perform executive function, such as General Practitioner Cognitive Assessment (GPCOG) test, memory impairment screening, Mini-Mental State Examination (MMSE), California Verbal Learning Test, 2nd Edition, Short Form for Memory, Delis-Kaplan Executive Function System Test, etc.Examples of visual tests include, for example, visual acuity test, fundus examination, etc.

[0062] In some embodiments, the composition can be provided in combination with a second drug that is proven in the art to treat neurodegenerative disease or cognitive impairment.For example, several drugs, such as cholinesterase inhibitors (e.g., donepezil, rivastigmine, galantamine, tacrine), memantine, and vitamin E, have been shown to have some efficacy in treating the cognitive symptoms of Alzheimer's disease (e.g., memory loss, confusion, and problems with thinking and reasoning). As another example, several medications, such as citalopram (Celexa), fluoxetine (Prozac), paroxeine (Paxil), sertraline (Zoloft), trazodone (Desyrel), lorazepam (Ativan), oxazepam (Serax), aripiprazole (Abilify), clozapine (Clozaril), haloperidol (Haldol), olanzapine (Zyprexa), quetiapine (Seroquel), risperidone (Risperdal), and ziprasidone (Geodon), have been shown to have some effectiveness in treating the behavioral or psychiatric symptoms of Alzheimer's disease.

[0063] In some aspects of the subject methods, the methods further include measuring cognitive ability, vision, synaptic plasticity, etc. after treatment, e.g., using methods described herein or known in the art, and detecting a rate of reduction in cognitive / visual decline / loss of synaptic plasticity, stabilization of cognitive / visual ability / synaptic plasticity, and / or increase in cognitive / visual ability / synaptic plasticity after administration of the subject composition compared to the individual's cognitive / visual ability / synaptic plasticity before the subject composition was administered. In some examples, the determination is made by comparing the results of a cognitive test, vision test, or synaptic plasticity test to results of a test performed on the same individual at an earlier time, e.g., 1 week, 2 weeks, 1 month, 2 months, 3 months, 6 months, 9 months, 1 year, 2 years, 5 years, or 10 years or more ago. In other examples, the determination is made by comparing the results of the cognitive test, visual test, or synaptic plasticity test with the results of a test performed on a reference individual, e.g., a healthy individual who does not suffer from cognitive or visual impairments greater than those associated with the natural aging process.

[0064] "Cognition" refers to mental processes including attention and concentration, learning complex tasks and concepts, memory (acquiring, retaining, and retrieving new information in the short-term and / or long-term), information processing (dealing with information gathered by the senses), visuospatial functions (visual perception, depth perception, using mental imagery, copying drawings, constructing objects or shapes), language production and comprehension, verbal fluency (word finding), problem solving, decision making, and executive functions (planning and prioritization). Cognition is the capacity to process information, apply knowledge, and change preferences. "Cognitive plasticity" refers to the ability to learn, e.g., to learn complex tasks and concepts, similar to the ability to learn of undifferentiated organisms such as newborns or juveniles, e.g., humans, from birth to the prepubertal age of about 10 years. "Cognitive decline" refers to a gradual decrease in cognition, as evidenced by, for example, a decline in one or more of attention and concentration, learning complex tasks and concepts, memory (acquiring, retaining, and retrieving new information in the short-term and / or long-term), information processing (dealing with information gathered by the senses), visuospatial function (visual perception, depth perception, use of mental imagery, copying drawings, constructing objects or shapes), language production and comprehension, verbal fluency (word finding), problem solving, decision-making, and executive function (planning and prioritization). "Impaired cognitive ability", "cognitive decline", and "cognitive impairment" refer to a decline in cognitive ability compared to a healthy individual, for example, an age-matched healthy individual, or compared to the ability of an individual at an earlier time point, for example, 2 weeks, 1 month, 2 months, 3 months, 6 months, 1 year, 2 years, 5 years, or 10 years or more ago.

[0065] "Vision" refers to the ability to see an object. "Deteriorating vision" refers to a gradual decrease over time in the acuity, i.e., clarity, of an individual's vision. "Amblyopia" or "deteriorating visual function" refers to impaired vision, as compared to a healthy individual, e.g., an age-matched healthy individual. Methods for measuring visual acuity and visual function are also well known in the art, any of which can be used to identify individuals in need of treatment with the subject method and / or their responsiveness to treatment with the subject method. These include, for example, measuring an individual's ability to identify letters or numbers at a given distance according to a fixed standard. In some examples, the criteria can be the results of a visual acuity test performed by one or more age-matched individuals who experience visual acuity deterioration (i.e., a positive control) or do not experience visual acuity deterioration (i.e., a negative control). In some examples, the criteria can be the results of a task performed by the same individual at an earlier age, e.g., one week, one month, three months, six months, nine months, etc., to determine whether the individual suffers from visual acuity deterioration.

[0066] Excitatory / inhibitory imbalance may be a common pathophysiological mechanism and therefore a therapeutic target in autism spectrum disorder (ASD). For example, abnormalities in the expression of glutamate and GABA receptors have been observed in postmortem brains of people with ASD. In vivo, proton magnetic resonance spectroscopy ([1H]MRS) has revealed altered levels of glutamate and glutamine in the cortex and basal ganglia of children and adults with ASD. Furthermore, reduced GABA has been reported in several brain regions of children with ASD. Electrophysiological and biochemical investigations in animal models of ASD have revealed brain region- and model-specific imbalances in E / I function.

[0067] Convulsive syndromes are multicausal phenomena in which a reduction or absence of neuronal inhibition mediated by GABA is a relatively common phenomenon. A reduction in inhibitory GABAergic tone is associated with an increase in neuronal excitability that promotes excessive synchronization of neuronal electrical activity and the appearance of convulsive episodes. This can lead to a number of pathological processes, such as epileptic states. Studies in humans have shown that the expression of transporters for GABA is reduced in the hippocampus of epileptic patients, possibly leading to an increase in GABA in the synaptic cleft. In response, there is an internationalization (downregulation) of GABA receptors into the cytoplasm and a decrease in their number in the cell membrane, which reduces the response to GABA and increases the action of excitatory neurotransmitters.

[0068] Experimental evidence indicates a relationship between GABAergic dysfunction and affective disorders such as stress, anxiety, depression, and addictive behaviors, particularly those associated with alcoholism.

[0069] Anxiety and depression are emotional disorders that often occur simultaneously in the same patient, and some researchers suggest that both conditions may have similar pathophysiological mechanisms. Reduced GABAergic tone may be present in both anxiety disorders and more complex conditions such as major depression. Functional brain imaging studies of patients with depression have shown lower levels of GABA at the cortical level, and in experimental rat models, reduced expression of GABA-A receptors has been observed to produce behavioral patterns similar to anxiety. GABA is also involved in the pathophysiology of panic disorder along with serotonin and dopamine.

[0070] The neurobiological effects of alcoholism, such as acute and chronic intoxication, convulsive episodes, psychotic states, Wernicke-Korsakoff syndrome, and fetal alcohol syndrome, are manifestations of the effects and consequences of ethanol, a GABAergic agonist, on the glutamatergic system. Acute ingestion of ethanol enhances GABAergic transmission (by increasing chloride conductance through GABA receptors) and inhibits glutamatergic function (by decreasing cathonic conductance through NMDA receptors). Paradoxically, the development of tolerance associated with chronic ethanol ingestion leads to a decrease in GABAergic function and an increase in glutamatergic activity. Long-term inhibition of NMDA receptors by ethanol leads to the development of hypersensitivity, and acute withdrawal of ethanol leads to a marked increase in the activity of postsynaptic neurons involving various circuits such as dopaminergic, noradrenergic, and glutamatergic systems that may result in glutamate-induced neurotoxicity.

[0071] GABA is also involved in the pathophysiology of schizophrenia. GABA function is reduced in brain regions that show structural changes observed in computed tomography and magnetic resonance studies. These reported structural changes are associated with negative symptoms in patients, premorbid dysfunction, and reduced turnover of dopamine and serotonin. In both schizophrenia patients and animal models, there are other findings related to GABA, such as a reduced density of GABAergic neurons, structural changes in the receptors, and impaired reuptake of this neurotransmitter. This accumulating evidence suggests the involvement of GABA in the development of this disease.

[0072] GABAergic medications are the treatment of choice in epilepsy to increase inhibitory tone to reduce neuronal cortical hyperexcitability.

[0073] In vivo imaging In some embodiments, methods are provided for the use of in vivo imaging, for example, to localize or identify sites where cells of interest involved in glutamate or glutamine metabolism are located. In these embodiments, a detectably labeled agent is administered to an individual (e.g., by injection) and the labeled cells are identified using standard imaging techniques, including, but not limited to, positron emission tomography, magnetic resonance imaging, computed tomography scanning, and the like.

[0074] For diagnostic in vivo imaging, the type of detection instrument available is the primary factor in selecting a given radionuclide. The radionuclide selected must have a type of decay that is detectable by a given type of instrument. In general, any conventional method for visualizing diagnostic imaging can be utilized in accordance with the present invention. Another important factor in selecting a radionuclide for in vivo diagnosis is that its half-life is long enough to still be detectable upon maximal uptake by the target tissue, but short enough that harmful radiation of the host is minimized.

[0075] The detectably labeled agent is used in conjunction with an imaging technique to analyze the expression of the target. In one embodiment, the imaging method is one of PET or SPECT, which are imaging techniques in which a radionuclide is administered synthetically or locally to the patient. The subsequent uptake of the radiotracer is measured over time and used to obtain information about the target tissue. Due to the high energy (gamma) emission of the particular isotopes utilized and the sensitivity and sophistication of the instruments used to detect them, the spatial distribution of the radioactivity can be inferred from outside the body.

[0076] Among the positron-emitting nuclides most commonly used in PET are: 11 C. 13 N, 15 O, and 18 F. Isotopes that decay by electron capture and / or gamma emission are used in SPECT, 123 I and99 Contains mTc.

[0077] Thus, suitable imaging labels include radiographic moieties (e.g., heavy metals and radioactive emitting moieties), positron emitting moieties, magnetic resonance contrast moieties, and optically visualized moieties (e.g., fluorescent or visible spectrum dyes, visible particles, etc.). Preferred radiolabels include compounds and chelates with relatively large atoms such as gold, iridium, technetium, barium, thallium, iodine, and their isotopes. The compositions and methods of the present invention preferably utilize radioimaging moieties with low toxicity, such as iodine or iodine isotopes. Radionuclides that emit radiation capable of penetrating the skull may be useful in scintillation imaging techniques. Radionuclides suitable for labeling include: 99 Tc, 111 In, and 67 Positron emitting moieties for use in the present invention include: 18 F, 11 C. 13 N, 15 O is one example.

[0078] Preferred magnetic resonance contrast moieties include chelates of chromium (III), manganese (II), iron (II), nickel (II), copper (II), praseodymium (III), neodymium (III), samarium (III) and ytterbium (III) ions. Due to their very strong magnetic moment, gadolinium (II), terbium (III), dysprosium (III), holmium (III), erbium (III) and iron (III) ions are particularly preferred. Examples of such chelates suitable for magnetic resonance spin imaging are described in U.S. Patent No. 5,733,522, which is incorporated herein by reference in its entirety.

[0079] Optically visible moieties for use as imaging moieties include fluorescent dyes, or visible spectrum dyes, visible particles, and other visible labeling moieties.Fluorescent dyes such as ALEXA dyes, fluoresceins, coumarins, rhodamines, bodipy Texas red, and cyanine dyes are useful when they can provide sufficient excitation energy to the site visually inspected.Endoscopic visualization procedures may be more compatible with the use of such labels.

[0080] formulation The agent may be administered as a pharmaceutical composition containing a pharma- ceutically acceptable excipient. The preferred form depends on the intended mode of administration and therapeutic application. Depending on the desired formulation, the composition may also contain a pharma- ceutically acceptable non-toxic carrier or diluent, which are defined as vehicles commonly used to formulate pharmaceutical compositions for animal or human administration. The diluent is selected so as not to affect the biological activity of the combination. Examples of such diluents are distilled water, physiological phosphate-buffered saline, Ringer's solution, dextrose solution, and Hank's solution. In addition, the pharmaceutical composition or formulation may also contain other carriers, adjuvants, or non-toxic, non-therapeutic, non-immunogenic stabilizers, etc.

[0081] As used herein, "commercially available" compounds include those available from Acros Organics (Pittsburgh PA), Aldrich Chemical (Milwaukee WI, including Sigma Chemical and Fluka), Apin Chemicals Ltd. (Milton Park UK), Avocado Research (Lancashire UK), BDH Inc. (Toronto, Canada), Bionet (Cornwall, UK), Chemservice Inc. (West Chester PA), Crescent Chemical Co. (Hauppauge NY), Eastman Organic Chemicals, Eastman Kodak Company (Rochester NY), Fisher Scientific Co. (Pittsburgh PA), Fisons Chemicals (Leicestershire UK), Frontier Scientific (Logan UT), ICN Biomedicals, Inc. (Costa Mesa CA), Key Organics (Cornwall UK), Lancaster Synthesis (Windham NH), Maybridge Chemical Co. Ltd. (Cornwall UK), Parish Chemical Co. (Orem UT), Pfaltz & Bauer, Inc. (Waterbury CN), Polyorganix (Houston TX), Pierce Chemical Co. (Rockford IL), Riedel de Haen AG (Hannover, Germany), Spectrum Quality Products, Inc. (New Brunswick, NJ), TCI America (Portland OR), Trans World Chemicals, Inc. (Rockville MD), Wako Chemicals USA, Inc. (Richmond VA), Novabiochem, and Argonaut Technology.

[0082] Compounds useful for co-administration with the active agents of the present invention can also be made by methods known to those skilled in the art. As used herein, "methods known to those skilled in the art" can be identified through various reference books and databases. Suitable reference books and articles detailing the synthesis or providing references to articles describing the preparation of reactants useful in the preparation of the compounds of the invention include, for example, "Synthetic Organic Chemistry", John Wiley & Sons, Inc., New York; S.R. Sandler et al., "Organic Functional Group Preparations," 2nd Ed., Academic Press, New York, 1983; H.O. House, "Modern Synthetic Reactions", 2nd Ed., W.A. Benjamin, Inc. Menlo Park, Calif. 1972; T.L. Gilchrist, "Heterocyclic Chemistry", 2nd Ed., John Wiley & Sons, New York, 1992; J. March, "Advanced Organic Chemistry: Reactions, Mechanisms and Structure", 4th Ed., Wiley-Interscience, New York, 1992. Specific and similar reactants may also be identified through indexes of known chemicals prepared by the Chemical Abstract Service of the American Chemical Society, available in most public and university libraries, as well as online databases (American Chemical Society, Washington, DC, may be contacted for more information at www.acs.org). Chemicals that are known, but not commercially available in catalogs, may be prepared by custom chemical synthesis companies, and many of the standard chemical supply companies (e.g., those listed above) offer custom synthesis services.

[0083] The active agent of the present invention and / or the compound administered therewith are incorporated into various formulations for therapeutic administration. In one aspect, the agent is formulated into a pharmaceutical composition by combining with a suitable pharma-ceutically acceptable carrier or diluent, and is formulated into a preparation in solid, semi-solid, liquid or gas form, such as tablets, capsules, powders, granules, ointments, solutions, suppositories, injections, inhalants, gels, microspheres, and aerosols. Thus, administration of the active agent and / or other compounds can be achieved in various ways, usually by oral administration. The active agent and / or other compounds can be systemic after administration, or can be localized by formulation or by using an implant that acts to retain the active dose at the implantation site.

[0084] In the pharmaceutical dosage form, the active agent and / or other compound may be administered in the form of their pharma- ceutically acceptable salts, or may be used alone or in suitable associations, as well as in combination with other pharma- ceutically active compounds.As mentioned above, the agents may be combined to provide an active cocktail.The following methods and excipients are illustrative and should not be construed as limiting the present invention.

[0085] For oral preparations, the agents may be used alone or in combination with suitable excipients to produce tablets, powders, granules or capsules, for example, with conventional excipients such as lactose, mannitol, corn starch or potato starch, with binders such as crystalline cellulose, cellulose derivatives, acacia, corn starch or gelatin, with disintegrating agents such as corn starch, potato starch or sodium carboxymethylcellulose, with lubricants such as talc or magnesium stearate, and, if desired, with diluents, buffers, wetting agents, preservatives and flavorings.

[0086] The formulations are typically provided in unit dosage forms, the term "unit dosage form" referring to physically discrete units suitable as unitary dosages for human subjects, each unit containing a predetermined amount of active agent in an amount calculated sufficient to produce the desired effect in association with a pharma- ceutically acceptable diluent, carrier or vehicle. The specifications for the unit dosage forms of the present invention depend on the particular conjugates used and the effect to be achieved, as well as the pharmacodynamics associated with each conjugate in the host.

[0087] Pharmaceutically acceptable excipients, such as vehicles, adjuvants, carriers, or diluents, are commercially available. In addition, pharma- ceutically acceptable auxiliary substances, such as pH adjusting and buffering agents, tonicity adjusting agents, stabilizers, wetting agents, etc., are commercially available. Any compound useful in the methods and compositions of the present invention may be provided as a pharma- ceutically acceptable base addition salt. A "pharma-ceutically acceptable base addition salt" refers to a salt that retains the biological effectiveness and properties of the free acid, and is not biologically or otherwise undesirable. These salts are prepared from the addition of an inorganic or organic base to the free acid. Salts derived from inorganic bases include, but are not limited to, sodium, potassium, lithium, ammonium, calcium, magnesium, iron, zinc, copper, manganese, aluminum salts, and the like. Preferred inorganic salts are ammonium, sodium, potassium, calcium, and magnesium salts. Salts derived from organic bases include, but are not limited to, salts of primary, secondary, and tertiary amines, substituted amines including naturally occurring substituted amines, cyclic amines, and basic ion exchange resins such as isopropylamine, trimethylamine, diethylamine, triethylamine, tripropylamine, ethanolamine, 2-dimethylaminoethanol, 2-diethylaminoethanol, dicyclohexylamine, lysine, arginine, histidine, caffeine, procaine, hydrabamine, choline, betaine, ethylenediamine, glucosamine, methylglucamine, theobromine, purine, piperazine, piperidine, N-ethylpiperidine, polyamine resins, etc. Particularly preferred organic bases are isopropylamine, diethylamine, ethanolamine, trimethylamine, dicyclohexylamine, choline, and caffeine.

[0088] Carriers can carry drugs in a variety of ways, including either covalently bound directly or via a linker group, and non-covalently bound association.Suitable covalently bound carriers include proteins such as albumin, peptides, and polysaccharides such as aminodextran, each of which has multiple sites for binding moieties.The nature of the carrier can be either soluble or insoluble for the purposes of the present invention.

[0089] Acceptable carriers, excipients, or stabilizers are nontoxic to recipients at the dosages and concentrations employed and include buffers such as phosphate, citric acid and other organic acids, antioxidants including ascorbic acid and methionine, preservatives (e.g., octadecydimethylbenzylammonium chloride, hexamethonium chloride, benzalkonium chloride, benzethonium chloride, phenol, butyl or benzyl alcohol, alkyl parabens such as methyl or propyl paraben, catechol, resorcinol, cyclohexanol, 3-pentanol, and m-cresol), low molecular weight (less than about 10 residues) polypeptides, serum albumin, , proteins such as gelatin or immunoglobulins, hydrophilic polymers such as polyvinylpyrrolidone, amino acids such as glycine, glutamine, asparagine, histidine, arginine or lysine, monosaccharides, disaccharides and other carbohydrates including glucose, mannose or dextrins, chelating agents such as EDTA, sugars such as sucrose, mannitol, trehalose or sorbitol, salt forming counterions such as sodium, metal complexes (e.g., Zn-protein complexes), and / or non-ionic surfactants such as TWEEN®, PLURONICS® or polyethylene glycol (PEG). Formulations to be used for in vivo administration must be sterile. This is readily accomplished by filtration through sterile filtration membranes.

[0090] The active ingredient may also be entrapped in microcapsules, such as hydroxymethylcellulose or gelatin-microcapsules and poly-(methylmethacylate) microcapsules, respectively, prepared by coacervation techniques or by interfacial polymerization, in colloidal drug delivery systems (e.g., liposomes, albumin microspheres, microemulsions, nanoparticles and nanocapsules), or in macroemulsions. Such techniques are disclosed in Remington's Pharmaceutical Sciences 16th edition, Osol, A. Ed. (1980).

[0091] The composition can be prepared as an injectable, either as a liquid solution or suspension, or as a solid form suitable for solution or suspension in liquid vehicles prior to injection.The preparation can also be emulsified or encapsulated in liposomes or microparticles, such as polylactide, polyglycolide, or copolymers, for enhanced adjuvant effect, as explained above.See Langer, Science 249:1527,1990, and Hanes, Advanced Drug Delivery Reviews 28:97-119,1997.The agent of the present invention can be administered in the form of a depot injection or implant formulation, which can be formulated in such a way that it allows sustained or pulsatile release of the active ingredient.The pharmaceutical composition is generally formulated to be sterile, substantially isotonic, and in full compliance with all Good Manufacturing Practice (GMP) regulations of the United States Food and Drug Administration.

[0092] Toxicity of an active agent can be determined by standard pharmaceutical procedures in cell cultures or experimental animals, for example by determining the LD50 (the dose lethal to 50% of the population) or the LD100 (the dose lethal to 100% of the population). The dose ratio between the toxic effect and the therapeutic effect is the therapeutic index. The data obtained from these cell culture assays and animal studies can be used to further optimize and / or define the therapeutic and / or sub-therapeutic dose ranges (e.g., for use in humans). The exact formulation, route of administration and dosage can be chosen by the individual physician in view of the patient's condition.

[0093] experiment The following examples are presented to provide those of ordinary skill in the art with a complete disclosure and description of how to make and use the present invention, and are not intended to limit the scope of what the inventors regard as their invention, nor are they intended to represent that the following experiments are all or the only ones performed. Efforts have been made to ensure accuracy with respect to numbers used (e.g., amounts, temperatures, etc.), but some experimental error and deviation should be accounted for. Unless otherwise indicated, parts are parts by weight, molecular weight is weight average molecular weight, temperature is in degrees Celsius, and pressure is at or near atmospheric.

[0094] Abbreviations: 2-methylglutamate (2MeGlu), 2-methylglutamine (2MeGln), 4-aminopentanoic acid (4APA), acetonitrile (ACN), aminomethylphosphonic acid (AMPA), analysis of variance (ANOVA), bicinchoninic acid (BCA), ethylenediaminetetraacetic acid (EDTA), fluorescence imaging plate reader (FLIPR), gamma-aminobutyric acid (GABA), glutamic acid decarboxylase (GAD), high potassium Krebs-Ringer phosphate buffer (K-KRP), hydrophilic interaction chromatography (HILIC), intraperitoneal (IP), Krebs-Ringer phosphate (KRP), liquid chromatography-mass spectrometry (LCMS), multiple reaction monitoring (MRM), N-methyl-D-aspartic acid (NMDA), pharmacokinetic noncompartmental analysis (PKNCA), phosphate buffered saline (PBS), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), Stanford Behavioral and Functional Neuroscience Laboratory (SBFNL), Ultra Performance Liquid Chromatography (UPLC).

[0095] Example 1 Enantiomers of 2-methylglutamate and 2-methylglutamine selectively affect brain metabolism and behavior in mice Imbalance of excitatory and inhibitory neurotransmission is involved in a wide range of psychiatric and neurological disorders. Here, we test the hypothesis that insertion of a methyl group on the stereogenic alpha carbon of L-Glu or L-Gln affects the gamma-aminobutyric acid (GABA) shunt and the glutamate-glutamine cycle, and this molecule may be useful as a molecular imaging agent or a drug that affects behavior. (S)-2-methylglutamate, or (S)-2MeGlu, was efficiently transported to the brain and synaptosomes and released by membrane depolarization in a manner comparable to endogenous L-Glu. (R)-2MeGlu was less efficiently transported to the brain and synaptosomes, but was not released by membrane depolarization. Each enantiomer of 2MeGlu had limited activity across a panel of more than 30 glutamate and GABA receptors. Neither enantiomer of 2MeGlu was metabolized along the GABA shunt, but (S)-2MeGlu was selectively converted to (S)-2-methylglutamine or (S)-2MeGln, which was then slowly hydrolyzed back to (S)-2MeGlu in the brain. rac-2MeGln was also transported into the brain with similar efficiency to (S)-2MeGlu. A battery of behavioral tests in young adult wild-type mice demonstrated safety at single doses up to 900 mg / kg of (R)-2MeGlu, (S)-2MeGlu, or rac-2MeGln, and suppressed locomotor activity at single doses of 100 mg / kg or more of (R)-2MeGlu or (S)-2MeGlu. No effects on anxiety or hippocampal-dependent learning were evident. The enantiomers of 2MeGlu and 2MeGln show promise as potential pharmacological agents and imaging probes for cells that produce or transport L-Gln.

[0096] In addition to 2MeGlu, we evaluated its hypothetical metabolites, i.e., analogs of the major Glu metabolites methylated at the carbon atom located at the α-position in Glu. These include 2-methylglutamine (2MeGln, a Gln analog), 4-aminopentanoic acid (4APA, a GABA analog), 4OPA (4-oxopentanoic acid or levulinic acid, a SSA analog), and 4-hydroxypentanoic acid (4HPA, a GHB analog). α-KG and SA do not have corresponding methylated analogs, and the hypothetical carbon atom at the α-position is not possible without disrupting the existing CC bond. α-KG and SA connect Glu to the Krebs cycle, so 2MeGlu cannot enter the cycle like Glu.

[0097] result We used LC-MS / MS with HILIC and chiral HILIC-like chromatography to resolve all compounds of interest, including their structural isomers, present in biological matrices across a wide range of concentrations. Although the introduction of a methyl group on the α-carbon significantly reduced the ability of the stationary phase to resolve the enantiomers compared to the natural amino acid, we achieved baseline resolution of 2MeGlu and 4APA enantiomers without prior derivatization (Figure 8).

[0098] Evaluation of neurotransmitter-like properties was performed using mouse brain synaptosomes, a preparation of functional, mostly presynaptic nerve terminals. The uptake of both enantiomers of 2MeGlu was temperature dependent (Figure 2A), but the S enantiomer (similar to L-2MeGlu) was approximately three times faster than the R enantiomer (similar to D-2MeGlu). Among the potential 2MeGlu metabolites, only rac-4APA was transported into synaptosomes, whereas 4OPA and 4HPA were not (Figure 2B). We tested whether 2MeGlu was present in the neurotransmitter pool by subjecting preloaded synaptosomes to high potassium concentration-induced membrane depolarization. Both enantiomers of 2MeGlu were transported into synaptosomes during preloading, but their potassium-induced release from vesicular stores was different (Figure 2C). Although the synaptosomal concentration of the R enantiomer was not significantly altered by depolarization, the S enantiomer was released upon depolarization in a manner very similar to endogenous Glu, as shown by the relative difference in substrate concentration in samples incubated under low and high potassium conditions (Fig. 2E). When tested under identical conditions, rac-4APA showed a high potassium concentration-dependent release (Fig. 2D) similar to endogenous GABA (Fig. 2E). Thus, although (R)- and (S)-2MeGlu as well as rac-4APA were transported into synaptosomes, only (S)-2MeGlu and at least one enantiomer of 4APA entered the neurotransmitter pool.

[0099] Initial metabolic assays were also performed on mouse brain synaptosomes known to contain residual astroglial components comprising less than 5% of total terminals by electron microscopy or flow cytometry detection (Figure 9). Synaptosomal concentrations of rac-2MeGlu decreased slowly over time with an estimated half-life of 21 min and were not associated with the concomitant appearance of 4APA or any other 2Me analogues in the GABA shunt, indicating that the 2Me analogues were not efficiently metabolized by enzymes in this pathway. We hypothesized that 2MeGlu may have been metabolized to 2MeGln and / or released back into the extrasynaptosomal space (Figure 9). Indeed, rapid formation of 2MeGln along with a steady release of 2MeGlu was observed, accounting for the total concentration of all 2Me species over time; i.e., the total concentrations of both 2MeGlu and 2MeGln did not change significantly over time (P=0.70, repeated measures one-way ANOVA, n=5) (Figure 9), indicating that 2MeGln was the only major metabolic product of 2MeGlu in mouse synaptosomes.

[0100] GS is responsible for the brain metabolism of Glu to Gln. Consistent with the synaptosomal results, 2MeGlu was converted to 2MeGln by human GS in the presence of ammonium ions and ATP, but the reaction was highly stereoselective for the S enantiomer (Figure 3A). This is another stereochemical difference with Glu, both of which are amidated by GS. Our results are consistent with previous studies that showed that the reaction of rac-2MeGlu with GS in the presence of ATP released 50% of the inorganic phosphate obtained under identical conditions as L-Glu. The reverse reaction was tested in vitro using human glutaminase GLS1, a phosphate-dependent amidohydrolase that accounts for more than 50% of the glutaminase activity in the brain. To overcome analytical interference caused by traces of 2MeGlu present in synthetic 2MeGln, catalytic hydrolysis was performed in H2O-enriched buffer. 2MeGlu and 2MeGlu- 18The simultaneous detection of O allowed us to distinguish between newly formed 2MeGlu and any pre-existing impurities, thereby quantifying only the former (Figure 3B). The appearance of 2MeGlu in samples containing rac-2MeGln indicated that at least one enantiomer of 2MeGln is a substrate for human GLS1, albeit relatively slow, with an apparent reaction rate about 35-fold lower compared to that of Gln (65 μM / min vs. 1.9 μM / min). Chiral analysis of isotopically labeled hydrolysis products indicated that the S enantiomer is the exclusive product of the GLS1-catalyzed reaction (Figure 3C).

[0101] Incubation of primary mouse brain astrocytes with each enantiomer of 2MeGlu confirmed the stereoselective nature of 2MeGln formation observed in synaptosomes and in vitro GS (Figure 4). The S enantiomer was transported into astrocytes and then converted to 2MeGln. In contrast, the R enantiomer was not detected in significant amounts in astrocytes and no conversion to 2MeGln was detected. The endogenous substrate, isotopically labeled L-[1,2- 13 C]Glu, (S)-2MeGlu and L-[1,2- 13 2MeGln and [1,2-C]Glu were prepared from 13 We found that the intracellular concentrations of [C]Gln were similar (0.35 nmol / well vs. 0.26 nmol / well), but the extracellular concentrations were orders of magnitude different (0.4 nmol / well vs. 5.0 nmol / well), indicating that 2MeGln was transported from astrocytes to [1,2- 13 C]Gln. Samples using racemic 2MeGlu as substrate followed the pattern of the S enantiomer, but concentrations were consistently reduced by 60-70%.

[0102] Enzymatic hydrolysis of 2MeGln back to 2MeGlu to complete the glutamate-glutamine cycle was examined in mouse primary cerebral cortical neuron cultures (Figure 4C). 2MeGlu was detected in mouse neurons because traces of 2MeGlu were present in the 2MeGln synthesis products, although it was unclear whether it was a product of intracellular enzymatic hydrolysis of 2MeGln or a product of direct transport from the medium. The observed uptake of both enantiomers of 2MeGlu in synaptosomes, and the hydrolysis of at least one enantiomer of 2MeGln by human GLS1, suggested that both mechanisms contribute to the intracellular presence of 2MeGlu in neuronal cultures. For comparison, isotopically labeled L-[1,2- 13 Identical experiments were performed in primary cortical neuron cultures with intracellular [1,2-C]Gln. 13 C]Gln was 2-fold lower than 2MeGln in the corresponding samples, whereas [1,2- 13 C]Glu was more than 5-fold lower in cells than 2MeGlu. 13 Together with the presence of [C]Glu, these results suggest that 13 These results suggest that [C]Gln is enzymatically hydrolyzed and transported out of cells at a higher rate than 2MeGln.

[0103] In summary, the above in vitro, synaptosomal, and primary cell culture experiments indicate that 2MeGlu and 2MeGln, while transported in and out of neurons and astrocytes similar to their non-methylated endogenous analogues, have a more restricted, stereochemically dependent, metabolic pathway. (S)-2MeGlu and (S)-2MeGln were shown to be substrates for GS and GLS1, respectively, whereas their R enantiomers were not. In addition, the relatively low extracellular release rate of endogenously synthesized 2MeGln suggests that the amidated product is partially trapped in the primary astrocytes in which it was generated.

[0104] Since GS is important for the proliferation of several cancer cells, we determined the effects of both 2MeGlu enantiomers and rac-2MeGln on the proliferation of glutamine-dependent MDA-MB-231 and SK-OV-3, and glutamine-independent MCF-7. Cell viability assays were performed by BPS Bioscience, and none of the test compounds significantly inhibited cell proliferation (IC) in any of the three cell lines. 50 These results showed that none of the compounds showed significant inhibitory activity (IC 50 >1 mM), consistent with our GLS1 inhibition assay (Figure 10).

[0105] Next, we investigated the pharmacokinetics of 2Me compounds in mouse blood and brain (Figure 5). All compounds reached maximum serum concentrations within 15 min of intraperitoneal (IP) administration and were substantially cleared from the blood within 60 min (Figure 5A). All compounds tested entered the brain where their kinetic profiles differed substantially (Figure 5B). (R)-2MeGlu brain concentrations peaked within 5 min at 30 pmol / mg protein and decreased over time with an estimated half-life of approximately 70 min. (S)-2MeGlu reached a maximum brain concentration of 50 pmol / mg protein after 25 min, but was actively converted to its only known metabolite, 2MeGln, whose concentration rose monotonically to over 250 pmol / mg protein at 120 min. Thus, (S)-2MeGlu and its metabolite (S)-2MeGln accumulated in the brain 10-fold more than (R)-2MeGlu. Administered rac-2MeGln achieved peak brain concentrations of 2MeGln more quickly (25 min) than injection with (S)-2MeGlu, which then remained relatively constant until 120 min. Interestingly, the concentration of 2MeGln in mouse brain at the last time point (120 min) was nearly identical whether (S)-2MeGlu or rac-2MeGln was administered, indicating that (S)-2MeGlu can be efficiently metabolized to 2MeGln in mouse brain and function as a prodrug / precursor. A common feature observed with both (S)-2MeGlu and rac-2MeGln is the appearance of 2MeGlu at 60 and 120 min. Previously presented results from the GLS1 enzyme assay suggested that (S)-2MeGln undergoes slow enzymatic hydrolysis to (S)-2MeGlu. Pharmacokinetic studies in mice are consistent with that observation, with the delayed appearance of 2MeGlu in the brain after the administered compound has been cleared from the blood indicating that 2MeGlu is slowly metabolized from 2MeGln accumulated in the brain, regardless of whether the original source was rac-2MeGln or (S)-2MeGlu.Finally, brain levels of endogenous Glu, Gln, or GABA were also determined as part of these experiments, and two-way ANOVA showed that endogenous brain levels of Glu, GABA, or Gln were not significantly altered by any of the three compounds administered at 100 mg / kg, or by times between 5 and 120 minutes after compound administration.

[0106] Next, we investigated the pharmacodynamics of the enantiopure glutamate mimetic compounds against a broad panel of glutamate and GABA receptors in both binding and functional assays (summarized in Table 1 and detailed in Tables 2-6). We purposefully assayed the 2MeGlu enantiomers for activity against both glutamate and GABA receptors in the case of receptor class switching, such as occurs with α-methyldopamine. Both compounds had weak to no significant activity against a number of glutamate and GABA receptors screened. Interestingly, (S)-2MeGlu did not interact significantly with any of the receptors tested. (R)-2MeGlu showed weak antagonist behavior against GluN2A, one of the four isoforms of the glutamate-binding subunit of the N-methyl-O-aspartate (NMDA) receptor.

[0107] [Table 1]

[0108] Our data suggested that 2MeGlu was a pseudoneurotransmitter that also interfered with the glutamate-glutamine cycle. Researchers at the Stanford Behavioral and Functional Neuroscience Laboratory (SBFNL), blinded to the identity of the compounds being tested, performed extensive screening for safety and tolerability, followed by learning and memory testing, as well as behavioral screening of transgenic mice with glutaminase deficiency.

[0109] Male 2-month-old healthy mice were injected with a single dose of (R)-2MeGlu, (S)-2MeGlu, or rac-2MeGln (100, 300, or 900 mg / kg IP) and then immediately assessed by novel cage observation and for survival. Only one mouse died 10 days after 900 mg / kg (R)-2MeGlu. Distance traveled in the novel cage was significantly decreased in a dose- and time-dependent manner for both (R)-2MeGlu and (S)-2MeGlu (P<0.001 for each, n=3), showing a marked decrease in response to novelty / locomotor activity while maintaining vigilance and responsiveness (Figure 6A and Figure 11). Next, we used a new group of male 2-month-old mice to perform a behavioral test battery called SHIRPA (measuring 23 sensorimotor functions and well-being), activity chamber open field assessment, and then withdrawal from the hot plate (n=6 per group) after a single IP injection of one of the three compounds or vehicle at 100 or 30 mg / kg. At the 100 mg / kg IP dose, there was no difference in mortality, latency to withdraw from the hot plate, or any SHIRPA score, except for motor activity, for (R)-2MeGlu or (S)-2MeGlu. The distance traveled in the activity chamber was significantly reduced for (R)-2MeGlu or (S)-2MeGlu compared to vehicle at all time points up to 6 minutes after injection, with no significant difference in the distance traveled beyond 9 minutes. rac-2MeGln was not significantly different from vehicle at any time point (Figure 6B). We repeated the acute exposure experiment here in a separate set of mice using 30 mg / kg or vehicle IP and observed a small but significant decrease in distance traveled only 11 min after injection of (R)-2MeGlu and rac-2MeGln (Figure 6C). No significant differences in SHIRPA scores or latencies to withdraw from the hot plate were observed in the 30 mg / kg IP dose group.

[0110] Subsequent static blinded experiments at SBFNL followed the behavioral effects of chronic low doses of (S)-2MeGlu, (R)-2MeGlu, or rac-2MeGln in drug naive male 2-month-old C57Bl / 6 mice administered 10 mg / kg / day or vehicle IP for 1 month. Behavioral testing (n=10 mice per group) began 1 week after chronic treatment and was performed according to well-established protocols for activity chambers and elevated plus maze (week 1 of testing), Y-maze (week 2 of testing), Morris water maze (weeks 2 and 3 of testing), and fear conditioning (week 4 of testing). Over the course of one month, there was no mortality and no significant effect on body weight during treatment, distance traveled in the activity chamber (Figure 6D), time spent in the open arms of the elevated plus maze (Figure 12), spontaneous alternation in the Y-maze (Figure 13), or learning in the Morris water maze (Figure 14). In the fear conditioning paradigm, all treatment groups showed comparable learning of the sound-shock association on day 1 (Figure 15). There was no significant effect of treatment compared to the vehicle-treated group on contextual recall on day 2 (Figure 7A), indicating comparable hippocampal memory recall between the experimental groups, consistent with the Morris water maze results. Finally, no significant differences were detected in freezing during cue recall or tone presentation on day 3 between drug and vehicle-treated groups (Figure 7B, Figure 16).

[0111] Methylation of the alpha carbon of neurotransmitter precursors is used with L-dihydroxyphenylalanine (L-DOPA) to make aldomet or α-methyldopa, one of the first and still used antihypertensive drugs, and with L-tryptophan to make a serotonergic PET imaging agent. Racemic 2MeGlu is commonly synthesized from levulinic acid and has been used in enzyme studies, as a potential effector of glutamate receptors, transporters, and brain tumor cell proliferation, in tissue sections as a potential effector of dopamine release, ammonia balance, calcium uptake, and metabolic activation receptors, and in animals to moderate induced cycling behavior. Enantiomers of 2MeGlu are obtained by separating the racemate by various methods, and (S)-2MeGlu or (R)-2MeGlu have been synthesized by various approaches. (S)-2MeGlu has been tested as an inhibitor of EAAT1 / 2 transporters. Despite the use of rac-2MeGlu as the congener in these experiments, no one has investigated the metabolic effects of the enantiomers of 2MeGlu or 2MeGln in the brain or their potential enantiospecific activity in animals. Here, we tested the hypothesis that the enantiomers of 2MeGlu or 2MeGln selectively modulate metabolism of the GABA shunt or glutamate-glutamine cycle and act as useful pharmacological or imaging agents.

[0112] By design, 2-MeGlu was not a substrate for GAD or GLDH, and therefore did not proceed through the GABA shunt or undergo oxidative deamination. The S enantiomer (the L isomer by convention used for natural amino acids) was avidly transported to synaptosomes and stored and released like L-Glu. While replacing L-Glu in the neurotransmitter pool, (S)-2MeGlu had no significant activity across a broad range of glutamate and GABA receptors. Taken together, these data support the classification of (S)-2MeGlu as a pseudoneurotransmitter. We demonstrated that only (S)-2MeGlu was a substrate for GS, thereby allowing it to enter the glutamate-glutamine cycle. However, (S)-2MeGlu was not an efficient substrate for the reverse reaction. The net effect in vivo was that the pseudoneurotransmitter (S)-2MeGlu rapidly accumulated in the brain as (S)-2MeGln, which was then slowly converted back to (S)-2MeGlu. Exposure to rac-2MeGln resulted in a comparable but more rapid appearance of 2MeGln in the brain, accompanied by a slow generation of 2MeGlu over time. These properties lead us to propose that (S)-2MeGlu or 2MeGln may have useful applications as pharmacological agents to alter the excitatory / inhibitory balance in the brain, and possibly as imaging agents for GS-expressing or Gln-transporting cells.

[0113] (R)-2MeGlu, as expected, was not a substrate for GAD and did not proceed through the GABA shunt. (R)-2MeGlu was transported to synaptosomes but did not enter the neurotransmitter pool, suggesting that (R)-2MeGlu is a substrate for neuronal membrane trafficking but not for synaptic vesicle trafficking. (R)-2MeGlu had some weak activity at the GluN2A subunit of the NMDA receptor. (R)-2MeGlu was also transported to mouse brain, but much less efficiently than the S enantiomer. (R)-2MeGlu was not a substrate for GS and therefore did not enter the glutamate-glutamine cycle. The net effect was that (R)-2MeGlu was isolated from the normal metabolism of L-Glu, L-Gln, or GABA and had access to the brain and synaptic, but not vesicular, compartments with some weak activity at glutamate receptors.

[0114] The enantiomer-specific biochemical and metabolic properties of 2MeGlu or 2MeGln demonstrate that they may have useful applications as molecular imaging agents for GS-expressing or Gln-transporting cells and as pharmacological agents that can alter the excitatory / inhibitory balance. Therefore, we pursued safety and behavioral studies in young adult healthy male mice. Acute, high doses of (S)-2MeGlu, (R)-2MeGlu, or rac-2MeGln had minimal mortality, and (R)-2MeGlu or (S)-2MeGlu caused a transient, marked decrease in response to novelty / locomotor activity while remaining alert and responsive to ambient noise and gentle touch. This striking acute effect on mouse behavior observed at 100 mg / kg IP and higher doses may be due to a transient impairment of glutamatergic neurotransmission due to the ability of both enantiomers of 2MeGlu to be metabolized by GAD. The utility of such impaired responses to novel / motor activity has utility in the management of patients undergoing treatment or imaging sessions, as well as in the treatment of neurological and psychiatric disorders that result in part from an imbalance in excitatory and inhibitory neurotransmission.

[0115] Materials: (R)-2-methylglutamic acid, (S)-2-methylglutamic acid, and rac-2-methylglutamine were made from racemic form by order from Concept Life Sciences (Cheshire, UK). Buffer S (isotonic buffered sucrose solution): 0.32 M sucrose, 1 mM EDTA, 5 mM Tris-HCl pH 7.4. Buffer KRP (normal Krebs-Ringer phosphate buffer): 118.0 mM NaCl, 4.65 mM KCl, 1.23 mM CaCl2, 1.18 mM KH2PO4, 3.54 mM MgSO4, 15.64 mM Na2HPO4, 10 mM glucose. Buffer K-KRP (high potassium Krebs-Ringer phosphate buffer): 84.3 mM NaCl, 40.5 mM KCl, 1.23 mM CaCl2, 1.18 mM KH2PO4, 3.54 mM MgSO4, 15.64 mM Na2HPO4, 10 mM glucose.

[0116] Preparation of synaptosomes. Mouse brain synaptosomes were prepared according to published methods. For details, see Supplementary Methods. For experiments, 500 μL aliquots of synaptosomal suspension were transferred to pre-chilled microcentrifuge tubes. Centrifugation was performed at 8,000 g for 4 min at 4 °C, and all samples were stored at -80 °C, unless otherwise stated.

[0117] Synaptosomal neurotransmitter uptake assay. Each tube was added with 5 μL of test compound solution in KRP buffer (final concentration 10 μM) or KRP buffer alone. Samples were incubated at 4° C. or 37° C. for 1, 10, or 30 minutes, then immediately centrifuged and washed twice by resuspension-centrifugation with 0.5 mL of S buffer. The resulting pellet was resuspended in 170 μL of 0.1% aqueous formic acid and mixed with 330 μL of ACN.

[0118] Potassium-induced neurotransmitter release assay. To each tube, 2.5 μL of test compound solution in Buffer KRP (final concentration 100 μM) or Buffer KRP alone was added. Samples were incubated at 37° C. for 15 min, briefly cooled on ice, then immediately centrifuged and washed twice with Buffer KRP. The resulting pellet was then resuspended in either Buffer KRP (500 μL) or Buffer K-KRP (500 μL). Samples were either immediately centrifuged or incubated at 37° C. for 5, 10, or 15 min, then centrifuged and washed with Buffer KRP. The resulting pellet was resuspended in 400 μL of 60% ACN containing 2.5 μM Glu-d5 and 2.5 μM Gln-d5 as internal standards.

[0119] Metabolism in the GABA shunt pathway in synaptosomes. To each tube, a 5 μL aliquot of test compound solution in buffer KRP (final concentration 100 μM) or buffer KRP alone was added. Samples were incubated at 37° C. for 15 min, briefly cooled on ice, then immediately centrifuged and washed twice by resuspension-centrifugation with buffer S (0.5 mL). The pellet was then resuspended in buffer KRP (500 μL). Samples were then either immediately centrifuged or incubated at 37° C. for 5, 10, 15, 20, 25, or 30 min, then centrifuged and washed by resuspension-centrifugation with buffer S (0.5 mL). The resulting pellet was resuspended in 170 μL of 0.1% formic acid in water mixed with 330 μL of ACN.

[0120] Metabolism in the glutamate-glutamine cycle in synaptosomes. To each tube, 5 μL of 2MeGlu solution in buffer KRP (final concentration 100 μM) or buffer KRP alone was added. Samples were incubated at 37° C. for 15 min, briefly cooled on ice, then immediately centrifuged and washed twice by resuspension-centrifugation with buffer S (0.5 mL). The pellet was then resuspended in buffer KRP (200 μL). Samples were then kept on ice or incubated at 37° C. for 10, 20, 30, 40, or 50 min and then cooled on ice. All samples were then centrifuged, 200 μL of supernatant was collected, and the pellet was suspended in 200 μL of 80% ACN. The supernatant and pellet suspension were diluted with 250 μL of ACN and 50 μL of 10 μM d5-Glu in water as an internal standard.

[0121] Catalysis of 2MeGlu C5 amidation by human glutamine synthetase. The procedure was adapted from an existing protocol. Recombinant human glutamine synthetase (final concentration: 5 ng / mL) was added to a reaction mixture in a 1.5 mL microcentrifuge tube containing 10 mM substrate, 10 mM ATP, 20 mM MgCl2, 40 mM NH4Cl, 25 mM 2-mercaptoethanol in 100 mM imidazole-HCl buffer, pH 7.0. The tube was incubated at 37 °C in a pre-heated thermomixer and shaken at 600 rpm (30 s on, 30 s off). 5 μL aliquots were withdrawn in triplicate every 5 min and immediately diluted in 195 μL cold 60% ACN containing 10 μM Glu-d5 and Gln-d5 as internal standard in a 96-well plate. After all samples were collected, 200 μL of ACN was added to all wells and the plates were shaken at 1000 rpm for 5 minutes at room temperature and then stored at −80° C. until analysis.

[0122] Catalysis of 2MeGln hydrolysis by GLS1 glutaminase. The procedure was adapted from an existing protocol. 20% of the atoms 18 10 mM rac-2MeGln or L-Gln- in 100 mM phosphate, pH 7.4 buffer made in 1000 water.13 Recombinant GLS1 (final concentration: 5ng / mL) was added to the reaction mixture in a 1.5mL microcentrifuge tube containing C2. The tube was incubated at 37°C in a pre-heated thermomixer and periodically shaken at 600 rpm (30 sec on, 30 sec off). 5μL aliquots were collected in triplicate every 5 min and immediately diluted in 195μL cold 60% ACN containing 10μM Glu-d5 and Gln-d5 as internal standard in a 96-well plate. After all samples were collected, the plate was shaken at 1000 rpm for 5 min at room temperature and then stored at -80°C. Prior to analysis, the plate was thawed and 10μL aliquots of the extracted reaction mixture were diluted with 190μL 90% acetonitrile.

[0123] Quantification of newly formed 2MeGlu in the presence of pre-existing trace amounts was performed as follows. 13 C2 vs Glu- 13 C2 18 The peak area ratio of Glu-O was calculated by 13 The average ratio values ​​were then applied to the directly measured 2MeGlu- 18 A hypothetical peak area for newly formed 2MeGlu was calculated based on the O peak area. The ratio of the newly formed 2MeGlu peak area to the total 2MeGlu peak area was applied to calculate the concentration of newly formed 2MeGlu from the total 2MeGlu concentration determined directly using the calibration curve.

[0124] Astrocyte transport and metabolism of 2MeGlu. Primary astrocytes from C57Bl / 6 mouse brain were cultured in complete astrocyte growth medium at 37°C with 5% CO2 on 96-well plates. Cells were exposed to 1 mM compound in 100 μL of medium for 2 h at 37°C. Supernatants were collected and centrifuged at 2,500g for 10 min at 4°C. Aliquots of 10 μL were diluted in 190 μL of 60% ACN containing 10 μM Glu-d5 and Gln-d5. Cells were quickly washed twice with 250 μL of cold PBS and suspended in 200 μL of 60% ACN containing 10 μM Glu-d5 and Gln-d5. All samples were shaken at 1000 rpm for 5 min and then stored at -80°C.

[0125] Neuronal transport and metabolism of 2MeGln. The procedure was adapted from an existing protocol. Wild-type (WT) C57BL / 6J mating pairs were housed according to the Stanford IACUC protocol. On day P0, pups were euthanized and cultured in cold HBSS (Ca 2+ or Mg 2+ Brains were dissected in cold HBSS (without PBS). Forebrains were microscopically dissected to isolate the cortex and hippocampus. These brain regions were minced in cold HBSS, then trypsinized at 37°C for 9 min, followed by trituration through two glass-polished Pasteur pipettes. The resulting cell suspension was passed through a 100 μm filter and sedimented at 250 g for 5 min to isolate single cells. The cell pellet was then resuspended in complete neurobasal medium (neurobasal medium + Glutamax + B-27 Plus Supplement + Pen / Strep) + 10% FBS and counted using a hemocytometer, resulting in a cell count of 1 × 10 per mL. 6Cells were plated in poly-D-lysine and laminin coated 24-well plates (1 mL per well). Cultures were grown in a tissue culture incubator at 37°C / 5% CO2. The medium was 50% replaced with fresh complete neurobasal medium without FBS on day in vitro (1DIV) and then replaced with the same medium every other day. At 3DIV, the medium was spiked with 2 μM AraC to limit glial proliferation. At 10DIV, the medium was completely replaced with 500 μL of neurobasal medium containing B-27 Plus Supplement+Pen / Strep without the addition of Glutamax but instead containing 1 mM substrate for 2 hours at 37°C. The supernatant was collected and centrifuged at 16000g for 5 min at 4°C. An aliquot of 10 μL was diluted in 190 μL of 60% ACN containing 5 μM Glu-d5 and Gln-d5. Cells were washed twice with 500 μL PBS and suspended in 200 μL 60% ACN containing 5 μM Glu-d5 and Gln-d5. All samples were shaken at 800 rpm for 5 min and then stored at −80° C. until analysis.

[0126] In vitro animal studies. Behavioral tests were performed on 2-month-old male C57Bl / 6 mice. We selected male mice because the historical controls of SBFNL are male mice. First, we evaluated the safety and tolerability of acute exposure to our novel chemical entities through a series of tests immediately after IP injection: maximum tolerated dose with novel cage observation at 100, 300, or 900 mg / kg, and then SHIRPA, activity chambers, and then hot plate latency with 100 or 30 mg / kg IP in different drug-naive mice. Second, we investigated the effects of chronic exposure to 10 mg / kg (a dose 3-fold lower than the dose with minimal acute effects on locomotor activity) with daily IP injections starting 1 week before assessment of locomotion in the activity chamber, as well as learning and memory with the elevated plus maze (week 1), or Y-maze (week 2), Morris water maze (weeks 2 and 3), and then fear conditioning (week 4) according to established protocols that did not include counterbalancing of the avoidance platform location. Animals were dosed daily from 3:00 pm to 5:00 pm after the end of each behavioral test session. Although the time from the first dose for each behavioral test differed, our experimental protocol allows for efficient testing of the chronic effects of novel compounds.

[0127] Materials. rac-2-Methylglutamic acid (catalog number M0229) and 4-oxopentanoic acid (catalog number L0042) were obtained from TCI America. rac-4-Hydroxypentanoic acid (as the sodium salt, catalog number EN300-176456) and rac-4-aminopentanoic acid (as the hydrochloride salt, catalog number EN300-81918) were obtained from Enamine. LC-MS grade acetonitrile (catalog number A955), formic acid (catalog number A117), and trifluoroacetic acid (catalog number A116) were obtained from Fisher Scientific. Isotopically labeled L-glutamic acid (2,3,3,4,4-d5, catalog number DLM-556; 1,2-13C2, catalog number CLM-2024) and L-glutamine (2,3,3,4,4-d5, catalog number DLM-1826; 1,2-13C2, catalog number CLM-2001) were purchased from Cambridge Isotope Laboratories. HPLC grade ammonium formate (catalog number 60-020-36) was obtained from Fluka.

[0128] C57Bl / 6 mouse brain primary astrocytes were purchased from Lonza, Basel, Switzerland (catalog number M-ASM-330). Astrocytes were cultured in culture medium (catalog number CC-3187) and supplemented with growth factors (catalog number CC-4123) to make complete astrocyte growth medium. The second passage of astrocytes cultured in complete astrocyte growth medium at 37°C and 5% CO2 was used for the experiments. Recombinant human GLS1 (catalog number SRP0516) was purchased from Sigma. Recombinant human GS (catalog number ab222354) was purchased from Abcam.

[0129] Chemical characterization of key compounds: (R)-2MeGlu: 1 H NMR (D2O, 500MHz): δ2.48(m,2H), 2.13(m,2H), 1.52(s,3H). 13 C{ 1H} NMR (DO, 126MHz): δ 177.1, 175.7, 60.7, 31.9, 29.0, 22.1. >99% purity (UPLC-ELSD), 95% ee (chiral LC-MS) (S)-2MeGlu: 1 H NMR (D2O, 500MHz): δ2.49(m,2H),2.15(m,2H),1.53(s,3H). 13 C{ 1 H} NMR (DO, 126MHz): δ 176.9, 175.5, 60.6, 31.8, 28.9, 22.0. >99% purity (UPLC-ELSD), 95% ee (chiral LC-MS) rac-2MeGln: 1 H NMR (D2O, 500MHz): δ2.38(m,2H),2.10(m,2H),1.52(s,3H). 13 C{ 1 H} NMR (D2O, 126MHz): δ177.7,176.0,60.9,32.7,29.9,22.2.>97% purity (UPLC-ELSD).

[0130] Protein concentration determination. 500 μL of synaptosomal preparation was centrifuged (8,000 g for 4 min at 4° C.) and the supernatant was discarded. The pellet was suspended in 200 μL of RIPA buffer and incubated on ice for 90 min. The suspension was then sedimented (14,000 g for 10 min at 4° C.) and the supernatant was used to determine the total protein concentration using a Pierce BCA Protein Assay Kit and a Biotek Epoch microplate spectrophotometer by measuring the absorbance at 562 nm.

[0131] LC-MS / MS Analysis, HILIC Conditions. LC-MS / MS HILIC analysis was performed using an Agilent 6470 Triple Quadrupole LC / MS System equipped with an Agilent 1290 Infinity II LC module. Prior to analysis, all samples were filtered through a Multiscreen Solvinert 0.45 μm PTFE filter plate into a polypropylene 0.5 mL 96-well plate. 2.5 μL of sample was injected onto an Acquity UPLC BEH Amide column (2.1 × 50 mm, 1.7 μm particle size, Waters, part no. 186004800) equipped with an Acquity UPLC In-Line Filter (Waters, part no. 205000343) and thermostated at 40 °C. Samples were eluted at a flow rate of 0.6 mL / min using one of three gradient methods. Method 1 was developed for rapid quantification of all investigated compounds in relatively dilute biological matrices (synaptosomal extracts, cell extracts, in vitro reaction supernatants) and used lower pH buffer A (5 mM ammonium formate in water containing 0.1% formic acid, pH 3.2) and buffer B (5 mM ammonium formate in 95:5 (v / v) acetonitrile-water containing 0.1% formic acid) with the following gradient: 0.0-2.5 min: linear gradient from 10% to 27.5% A; 2.51-3.0 min: hold at 45% A; 3.01-3.5 min: hold at 10% A. Method 2 is a modified version of method 1 for accurate quantification of low amounts of 2MeGlu in brain tissue homogenates, where the two isomeric analytes were found to partially overlap with the peak of interest and interfere with quantification. It used the same buffer system and a longer gradient method. i.e., 0.0-5.0 min: linear gradient of 0%-32.5% A; 5.01-6.0 min: held at 0% A. The mass spectrometer was operated in multiple reaction monitoring (MRM) positive mode with the capillary voltage set at 3.5 kV, the nebulizer gas held at 250 °C, and the superheated sheet gas held at 300 °C. In experiments in which isotopically labeled internal standards were added, the results were corrected accordingly.

[0132] LC-MS / MS analysis, chiral conditions. LC-MS / MS chiral analysis was performed using an Agilent 6470 Triple Quadrupole LC / MS System equipped with an Agilent 1290 Infinity II LC module. Prior to analysis, all samples were filtered through a Multiscreen Solvinert 0.45 μm PTFE filter plate into a polypropylene 0.5 mL 96-well plate. 1.0 μL of sample was injected onto a CROWNPAK CR-I(+) column (3.0 × 150 mm, 5 μm particle size, Daicel, part no. 53784) equipped with an Acquity UPLC In-Line Filter (Waters, part no. 205000343) and thermostated at 20 °C. Samples were diluted in 0.4 mL portions with Buffer C (96:4 ACN / water v / v, 0.1% TFA; parameters were varied in optimization experiments). -1 The mass spectrometer was operated in multiple reaction monitoring (MRM) positive mode with the capillary voltage set at 3.5 kV, the nebulizer gas held at 250 °C, and the heated sheet gas held at 300 °C.

[0133] Preparation of synaptosomes. Cerebral hemispheres from C57BL / 6 mice were homogenized in 3 mL of buffer S using a pre-cooled 5 mL Potter-ELV tissue grinder (800 rpm, 8 strokes). The crude homogenate was diluted with buffer S to a total volume of 4 mL and centrifuged at 1,000 g for 10 min at 4° C. The supernatant was collected and sedimented (10,000 g for 20 min at 4° C.). The supernatant was discarded and the pellet was washed by resuspension-centrifugation (8,000 g for 4 min at 4° C.) with buffer S (4 mL, ×1) and buffer KRP (2 mL, ×3). The resulting pellet was resuspended in 3 mL of buffer KRP and filtered on an Ultrafree-CL 5 μm PVDF centrifugal device (1,000 g for 4 min at 4° C.). The filtrate was diluted to 15 mL with ice-cold buffer KRP and kept on ice. The synaptosomal preparation was used immediately in the following experiments.

[0134] Synaptosomal neurotransmitter uptake assay. 96-well plate experiments: 250 μL aliquots of synaptosomal suspension were transferred to two 0.8 mL 96-well plates, one on ice (0° C. samples only) and one on a thermoblock (37° C. samples only) and equilibrated for 10 min. 5 μL of test compound (0.5 mM; final concentration: 10 μM) in Buffer KRP or Buffer KRP blank was added 10, 20, or 30 min before the end of incubation. "0 min" samples were prepared by placing test compound solutions in separate pre-cooled V-bottom 2 mL 96-well plates, and at the end of incubation, 200 μL aliquots of all samples were transferred to 2 mL 96-well plates and immediately centrifuged (2,500 g for 15 min at 4° C.). The resulting pellet was rinsed with buffer KRP followed by two centrifugations and then resuspended in 200 μL of 60% ACN containing 2.5 μM Glu-d5 as an internal standard and stored at −80° C. until analysis.

[0135] Pharmacokinetics for 2MeGlu and 2MeGln in mice. C57BL / 6 mice (Jackson Laboratory Cat. No. 000664) were administered 100 mg / kg IP. At the indicated times, mice were deeply anesthetized with isoflurane, blood was collected by cardiac puncture, and after clotting on ice, animals were perfused with cold PBS until internal organs turned pale and blood ceased to flow from the inferior vena cava. Whole brains were rapidly dissected and half frozen at -80°C until homogenized in ice-cold PBS (pH 7.4) using a probe ultrasonic homogenizer (Branson Sonifier 450, power: 5, cycle: 30%, time: 10 sec) on ice. Lysates were centrifuged (2,500 g for 15 min at 4°C) and supernatants were assayed using the Pierce BCA Protein Assay Kit (23225) using a BioTek Epoch plate spectrophotometer by recording absorbance at 562 nm. Two or three 10 μL aliquots of the homogenate were transferred to a 96-well plate and extracted with 190 μL of 60% acetonitrile in water containing 10 μM GABA-d6 or 10 μM Glu-d5 and Gln-d5 as internal standards. A 40 μL aliquot of the extract was then diluted with 120 μL of acetonitrile and prepared for LC-MS / MS analysis. Brain and serum half-lives were calculated using the "PKNCA" package for R. Endogenous levels of Glu, Gln and GABA were determined in the brains of mice used in the pharmacokinetic experiments. Glu, Gln and GABA specific MRM transitions were monitored simultaneously.

[0136] In vivo animal studies, maximum tolerated dose (MTD) and behavioral studies. Animals: Two-month-old naïve male C57Bl / 6 mice from Jackson Laboratory (Stock ID #000664) were group-housed in the Stanford University animal facility on a 12:12-h light / dark cycle (lights off 8:30 am, lights on 8:30 am) with free access to water and food. All behavioral testing was performed during the animal's dark cycle. All procedures followed National Institutes of Health guidelines and were approved by the Institutional Administrative Panel on Laboratory Animal Care (APLAC).

[0137] Administration. (R)-2MeGlu (30, 100, 300, or 900 mg / kg), (S)-2MeGlu (30, 100, 300, or 900 mg / kg), rac-2MeGln (30, 100, 300, or 900 mg / kg), and vehicle (PBS) were administered in an IP administration volume of 10 ml / kg. Three mice were administered the assigned drug (100, 300, or 900 mg / kg) or vehicle once and immediately placed in a new cage for novel cage observation. Subsequently, six mice were administered the assigned drug (30 or 100 mg / kg) or vehicle once and tested by SHIRPA, activity chamber, and then hot plate test.

[0138] Novel Cage Observation. Mice were dosed and immediately placed in the center of a clean Innovive disposable rat cage (dimensions: 17''L x 13.4''W x 7.8''H) with bedding and allowed to move freely while being automatically tracked. Mice were monitored with Ethovision XT tracking software for distance traveled and average speed during a 60-minute trial. After testing, mice were returned to their home cage. A new cage was used for each mouse.

[0139] Hot Plate Test. The hot plate apparatus (IITC Inc. Model 39) was set at 55°C ± 0.2. On the test day, the mouse was placed on the surface of the hot plate and covered with a clear glass cylinder (25 cm high and 12 cm diameter). A cut-off time of 30 seconds was assigned. A remote foot switch pad was used to control the start / stop / reset functions. Latency was recorded when paw licking or jumping first occurred.

[0140] SHIRPA. A modified version of the SHIRPA prescreening designed by Rogers et al. (1997) was used to assess the overall health and behavioral characteristics of mice during the first 5 min after drug administration. Testing was performed in three different testing locations: a cylindrical clear plastic viewing jar (15 cm high × 10 cm diameter), a polycarbonate cage (arena) with a 10 cm × 10 cm square on the floor, and a 1 cm × 1 cm wire grid. Testing began by placing the mouse in the clear plastic viewing jar for 60 s, and behavioral parameters were monitored and recorded. The mouse was then transferred to the open-top arena by releasing it from 25 cm above the arena floor. Once monitoring of parameters in the arena was completed, the mouse was removed from the arena by its tail. Behavioral parameters monitored were according to Portmann et al. (2014).

[0141] Open Field Activity Chamber. Evaluations were performed in an open field activity arena (Med Associates Inc., St. Albans, VT. model ENV-515) fitted with a three-panel infrared detector in a specially designed sound-attenuating chamber (Med Associates Inc., St. Albans, VT. MED-017M-027). The arena was 43 cm (L) × 43 cm (W) × 30 cm (H) and the sound-attenuating chamber was 74 cm (L) × 60 cm (W) × 60 cm (H). Mice were placed in the corners of the testing arena and allowed to explore the arena for 60 min while being automatically tracked. Parameters measured included distance traveled, speed, rearing, and time spent at the periphery and center of the arena. The periphery was defined as the zone 5 cm away from the arena wall. The arena was cleaned with 1% Virkon solution at the end of the trial. Novel cage observations (see above) and activity chamber open field assessments are not performed in a similar manner in our laboratory and do not represent the same behavioral results. The novel cage protocol is performed on a benchtop in a well-lit room using clean home cages and tests for habituation effects using video recording and scoring of behavioral performance. Additionally, the novel cage allows the tester to visualize seizures or other adverse events such as repetitive jumping. The activity chamber is in a sealed box and testing is performed without bedding, in the dark, and in a sound-proof chamber. The activity chamber uses an infrared beam to measure distance traveled without video recording.

[0142] In vivo animal studies; chronic efficacy studies using C57Bl / 6J mice Animals. Two-month-old naïve male C57Bl / 6 mice from Jackson Laboratory (Stock ID number 000664) were used in this study. Animals were housed as described above.

[0143] Administration. (R)-2MeGlu (10 mg / kg), (S)-2MeGlu (10 mg / kg), rac-2MeGln (10 mg / kg), and vehicle (PBS) were administered IP daily in a dosing volume of 10 ml / kg. The first dose was administered 1 week prior to behavioral testing and continued for 4 weeks during behavioral testing.

[0144] Activity chamber open field. Assessments were performed in the open field activity arena as described above for 30 min. At the end of the trial the arena was washed with 1% Virkon solution. Activity chamber open field assessments were performed after 1 week of exposure to compound or vehicle.

[0145] Elevated plus maze. The maze was made of acrylonitrile butadiene styrene (ABS) plastic and had two open and two closed arms, 30 cm long and 5 cm wide. The central area where the open and closed arms crossed was 5 cm x 5 cm. The open arms had 2 mm edges at the ends and the closed arms had 15 cm opaque walls. The maze was elevated 50 cm during testing and surrounded by privacy blinds. The maze was illuminated to 7 lux using red light throughout the entire test. Each mouse was released into the center of the maze and given 5 minutes to explore the maze. The duration and frequency in each zone of the maze were recorded using Ethovision (Noldus Information Technology, Wageningen, the Netherlands) tracking software. The maze was washed with 1% Virkon solution at the end of the trial. The elevated plus maze was performed one week after exposure to compound or vehicle.

[0146] Spontaneous alternation in the Y-maze. The Y-maze is made of plastic and has three arms in a "Y" shape. The arms are labeled Arm A, B, and C, Arm A is 20.32 cm (L) x 5 cm (W) 12.7 cm (H), and Arms B and C are 15.24 cm (L) x 5 cm (W), and 12.7 cm (H). This test is based on the rodent's willingness to explore a new environment and is designed to measure spontaneous alternation in rodents. Each mouse was placed in the center of the maze facing Arm B. The first entry was excluded from the data analysis because the animal was guided to the first arm entry by the experimenter. The number of arm entries and alternations was recorded for 5 min using an overhead camera. An arm entry is the entry of all four paws into a new arm of the maze. The apparatus was washed with 1% Virkon. The parameters recorded were % alternations and total number of entries into the arms. The Y-maze test was performed after 2 weeks of exposure to compound or vehicle.

[0147] Morris Water Maze. During hidden platform training (HPT), mice were given two trials with a 1 min intertrial interval (ITI) in a circular water tank (172 cm diameter) filled with opaque water at 22.0 ± 1.5 °C. Non-toxic tempera paint was used to make the water opaque. A circular platform (17 cm diameter) was submerged 1 cm below the water surface and placed in one of the four quadrants of the pool (quadrant 2). The release location into the pool was randomly selected to prevent spatial bias, and the platform was also relocated during reversal training. We performed a total of six trials before probe 1 (days 1 to 3), with two trials each day for three days of training. Specifically, mice were given a maximum of 60 s to find the submerged platform for each trial. The experimenter guided the mouse to the platform if it failed to find the platform within 60 s. After remaining on the platform for 15 s, the mouse was removed from the platform and placed in a dry cage with a paper towel. This process was repeated for three days. The next day (approximately 24 hours after the last training trial), the platform was removed from the pool and a 60-second probe trial was performed. After acquiring the data for the probe trial, the platform was replaced in the same location and the mice were given two additional training trials. Three days (approximately 72 hours) after the last training trial, a second probe trial was performed. The platform was relocated to a new quadrant (quadrant 4) after the second probe trial and the animals were trained in reversed hidden platform training (RHPT). The procedure for the RHPT was identical to that of the HPT and was performed for three days (days 7 to 9). A third probe trial was performed the next day (approximately 24 hours). The platform was relocated to quadrant 1 upon completion of the third probe trial. The ping-pong ball was raised from the underwater platform and two trials of visual platform training were given to ensure that the mice had no gross sensorimotor or visual impairments. The animals' escape latency, distance traveled, time spent in the zone, and speed were recorded using an Ethovision XT (Noldus Information Technology, Wageningen, Netherlands).Morris water maze testing was performed between 2 and 3 weeks of exposure to compound or vehicle.

[0148] Fear conditioning. A Coulbourn Instruments (Holliston, MA, USA) fear conditioning system and FreezeFrame software were used for the analysis. The experiment consisted of 1 day of training, 1 day of contextual testing, and 1 day of cue testing. The training and contextual testing chambers were identical with similar contexts. The walls were made of aluminum. The floor was a gray metal grid shipped from the US, and the chambers used yellow house lights and were scented with mint extract to create a unique scent for the chamber. The chambers were cleaned with 10% plain green solution (Sunshine Makers, Inc.) between each mouse. The cue testing chamber was circular, made of plastic, used blue house lights, and was scented with vanilla extract to create a unique context that was different from the training and contextual testing. This chamber was cleaned with 70% ethanol between each mouse. Both chambers were mounted in a specially designed sound-attenuating chamber. Each chamber had a speaker attached to the wall and contained an exhaust fan and a camera. On the first training day, mice were placed individually into the training chamber for 200 s. A tone (20 s, 80 dB, 2 kHz) was presented to the mice, followed by an electric shock (intensity 0.5 mA, 2 s) 18 s after the end of the tone (Misane et al. 2005, Burman 2014, Lugo et al. 2014). This procedure was repeated twice with a 60 s interval between the end of the shock and the next tone. The mice were removed from the chamber and returned to their home cage 60 s after the last shock. On the second day, the mice were returned to the training chamber without tone or shock for 15 min for contextual memory testing. On the third day, the mice were placed in the cue test chamber with a simple tone (20 s, 80 dB, 2 kHz) presented three times with an 80 s interval after 200 s of acclimation. Overall, the mice received tone and shock pairing only on the training day. The freezing behavior of the mice was recorded using an overhead camera. Fear conditioning testing was performed after 4 weeks of exposure to the compounds or vehicle.

[0149] We have shown that when studying cognitive enhancement in normal young control mice, overtraining of animals leads to saturation of behavioral learning, making it very difficult to show pharmacological improvements in behavioral paradigms. Therefore, we chose to reduce the number of training trials per day and the number of training days in the Morris water maze to increase the chance of observing drug effects. Similarly, in the fear conditioning task, we chose a lower shock intensity and fewer tone and shock (2x) pairings to increase the chance of observing pharmacological activity.

[0150] Receptor function and binding assays. All GABA A Functional assays of NMDA (GluN2A-GluN2D) and AMPA (GluA2) receptor subunits were performed by SB Drug Discovery as part of their CNS discovery panel using FLIPR technology. Briefly, receptor-expressing HEK293 cell lines were incubated in red membrane potential dye in HEPES:HBSS pH 7.4 buffer and fluorescence (λ) was measured upon addition of test and / or reference compounds to the solution. ex :488, λ ex The concentration of the test compound was monitored over time (approximately EC500:510-570). In the agonist assay, only the test compound was added. In the positive allosteric modulator assay, cells were preincubated with the test compound and then incubated with a low concentration (approximately EC500:510-570). 20 ) of the appropriate agonist was added. For antagonist assays, cells were preincubated with test compounds and then incubated with a high concentration (approximately EC 80 ) was added with the appropriate agonist. AIn the assays, GABA was used as the agonist, picrotoxin was used as the reference antagonist, and allopregnanolone was used as the reference positive allosteric modulator (PAM). In the NMDA assay, a mixture of glutamate, glycine, and CaCl2 was used as the agonist, MK801 was the reference antagonist, and pregnenolone sulfate or GNE9278 was used as the reference PAM. In the AMPA assay, glutamate was used as the agonist, CNQX was the reference antagonist, and cyclothiazide was used as the reference PAM. All compounds were tested in triplicate at seven concentration points, and EC50 / IC50 was determined, where applicable. Functional GABA B The assay uses human GABA B In RBL cells expressing the Ca(B1 / B2) receptor, 2+ Dependent fluorescence quantification was performed by Eurofins Discovery (Cerep). All compounds were tested in triplicate at a single concentration of 100 μM.

[0151] Nonspecific AMPA, kainate, and NMDA binding assays were performed using rat cerebral cortical membranes and radiolabeled [ 3 H]AMPA, 3 H]kainic acid, and [ 3 H]CGP39653 was used by Eurofins Discovery (Cerep). All compounds were tested at a single concentration of 100 μM in triplicate. mGluR1, mGluR2, mGluR5 and GABA B Binding assays were performed by Eurofins Discovery. mGluR1 assays were performed using rat cerebellar membranes and radiolabeled [ 3 mGluR2 assays were performed using recombinant Chem-1 cells and [H]quisqualic acid. 3 H]LY341495. B Binding assays were performed using recombinant CHO-K1 cells and 3 H]CGP-54626 and [ 3H]quisqualic acid, respectively. All compounds were tested in triplicate at a single concentration of 100 μM.

[0152] Cancer cell proliferation assay. Cancer cell proliferation assays against MDA-MB-231, SK-OV-3 and MCF-7 cell lines were performed by BPS Bioscience Inc., San Diego, CA. Potential inhibitors were tested in triplicate at concentrations ranging from 1 nM to 100 μM with cisplatin as a control compound. The incubation time was set to 72 hours and cell proliferation was assayed with the CellTiter-Glo assay from Promega.

[0153] GLS1 inhibition assay. GLS1 inhibition assays were performed using a GLS1 inhibitor screening assay kit from BioVision Inc, Milpitas, CA. Potential inhibitors were tested in the concentration range of 0.5 μM to 1 mM using initial kinetic measurements.

[0154] [Table 2]

[0155] [Table 3]

[0156] [Table 4]

[0157] [Table 5]

[0158] [Table 6]

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[0160] Example 2 Enantiomers of 4-aminopentanoic acid act as pseudo-GABAergic neurotransmitters and affect behavior in mice Imbalances in metabolic pathways linking excitatory and inhibitory neurotransmission are involved in multiple psychiatric and neurological disorders. In Example 1, we described the enantiomeric specific effects of 2-methylglutamate that has not been decarboxylated to the corresponding methyl analogue of gamma-aminobutyric acid (GABA):4-aminopentanoic acid (4APA). Here, we tested the hypothesis that 4APA also has enantiomeric specific actions in the brain. Mouse brain synaptosomal uptake (nmol / mg protein over 30 min) of (R)-4APA or (S)-4APA was time and temperature dependent, however, the R enantiomer had more uptake, reduction in endogenous GABA concentration, and release after membrane depolarization than the S enantiomer. (S)-4APA was more potent than several weak agonists (GABA A α4β3δ, GABA A α5β2γ2 and GABA B B1 / B2) and antagonists (GABA A α6β2γ2) activity, whereas (R)-4APA showed weak agonist activity at only GABAA α5β2γ2. Both 4APA enantiomers (100 mg / kg IP) were detected in mouse brain 10 min after injection and reached stable concentrations over 6 h at 1 h. Both enantiomers were rapidly cleared from mouse serum over 6 h. Two-month-old mice had no mortality after 100-900 mg / kg IP of each 4APA enantiomer, but had a similar dose-dependent decrease in distance traveled in a novel cage. Neither enantiomer at 30 or 100 mg / kg affected outcomes in 23 measures of well-being, activity chamber, or withdrawal from the hot plate. Our results demonstrate that the enantiomers of 4APA are active in the brain and that (R)-4APA may function as a novel pseudoneurotransmitter of GABA.

[0161] Here, we investigated the enantiomer-specific neurochemical and pharmacological properties of 4APA in vitro in mouse brain synaptosomes and in vivo in young adult mice (Figure 17).

[0162] Materials and Methods All mouse procedures followed National Institutes of Health guidelines and were approved by Stanford's Institutional Administrative Panel on Laboratory Animal Care (APLAC; approval number 31890).

[0163] (rac)-4-aminopentanoic acid (as the hydrochloride salt, catalog number EN300-81918), (R)-4-aminopentanoic acid (as the hydrochloride salt, catalog number BBV-38374677, optical rotation value +9.2°), and (S)-4-aminopentanoic acid (as the hydrochloride salt, catalog number BBV-38375018, optical rotation value -7.4°) were obtained from Enamine. These optical rotation values ​​were measured at 21° C., 589 nm, and 0.5 g / 100 ml HO according to the manufacturer's certificate of analysis.

[0164] LC-MS grade acetonitrile (catalog no. A955), formic acid (catalog no. A117), and trifluoroacetic acid (catalog no. A116) were obtained from Fisher Scientific. Isotopically labeled GABA (GABA-2,2,3,3,4,4-d6, catalog no. 615587) was purchased from Sigma. HPLC grade ammonium formate (catalog no. 60-020-36) was obtained from Fluka.

[0165] Solutions were prepared exactly as previously described (Wawro et al., 2021). Buffer S (isotonic buffered sucrose solution) was 0.32 M sucrose, 1 mM EDTA, 5 mM Tris-HCl pH 7.4. Buffer KRP (normal Krebs-Ringer phosphate buffer) was 118.0 mM NaCl, 4.65 mM KCl, 1.23 mM CaCl2, 1.18 mM KH2PO4, 3.54 mM MgSO4, 15.64 mM Na2HPO4, 10 mM glucose. Buffer K-KRP (high potassium Krebs-Ringer phosphate buffer) was 84.3 mM NaCl, 40.5 mM KCl, 1.23 mM CaCl2, 1.18 mM KH2PO4, 3.54 mM MgSO4, 15.64 mM Na2HPO4, 10 mM glucose.

[0166] Absolute configuration of 4APA enantiomers. The optical rotation of (R)-4APA has been reported as both positive (Otsuka et al. 1990, Mayol et al. 2016) and negative (Stenlake et al. 1955, Okamoto et al. 1979). The absolute configuration of the purchased 4APA was assigned by the manufacturer based on the optical rotation described above, but to clarify any ambiguity, we measured X-ray diffraction of crystals obtained from bulk (+)-4APA and used the diffraction data to assign the absolute configuration, which was further analyzed using chiral LCMS to confirm the major enantiomer of the bulk sample. We found that the X-ray diffraction measurements were consistent with the assignments made by the manufacturer. (+)-4APA was recrystallized from a methanol / isopropanol mixture. Diffraction data was collected using a Bruker D8 Venture diffractometer equipped with a PHOTON II detector. Measurements were performed using Cu Kα radiation at 100K. Crystals obtained from bulk (+)-4APA were the R enantiomer, consistent with the bulk of the sample. Crystallographic data have been deposited at the Cambridge Crystallographic Data Centre under accession number CCDC 2025613.

[0167] Chemical characteristics of enantiomer (R)-4APA HCl: 1H NMR (D2O, 500MHz): 3.43 (h, J = 6.7 Hz, 1 H), 2.55 (m, 2 H), 2.01 (m, 1 H), 1.87 (m, 1 H), 1.32 (d, J = 6.6 Hz, 3 H). 13 C[ 1 H]NMR(DO,126MHz): δ 177.1, 47.1, 29.8, 28.9, 17.3. 97% ee (chiral LC-MS).

[0168] (S)-4APA·HCl: 1 H NMR(D2O,500MHz):3.43(h,J=6.7Hz,1H),2.54(m,2H),2.01(m,1H),1.87(m,1H),1.32(d,J=6.6Hz,3H). 13 C[ 1 H]NMR(DO,126MHz): δ 177.1, 47.1, 29.8, 28.9, 17.2, 95% ee (chiral LC-MS).

[0169] Synaptosomes. Mouse brain synaptosomes were prepared exactly according to published methods (Gajera et al. 2019, Wawro et al. 2021). Briefly, for each biological replicate, cerebral hemispheres from one C57BL / 6 mouse were combined and homogenized in 3 mL of buffer S using a pre-cooled 5 mL Potter-ELV tissue grinder (800 rpm, 8 strokes). The crude homogenate was diluted to 4 mL with buffer S and sedimented at 1,000 g for 10 min at 4 °C. The supernatant was sedimented (10,000 g for 20 min at 4 °C) and the pellet was washed with buffer S (4 mL, ×1) and buffer KRP (2 mL, ×3) by resuspension-centrifugation (8,000 g for 4 min at 4 °C). The resulting pellet was resuspended in 3 mL of Buffer KRP and filtered on an Ultrafree-CL 5 μm PVDF centrifugation device (1,000 g for 4 min at 4° C.). The filtrate was diluted to 15 mL with ice-cold Buffer KRP and kept on ice. Synaptosome preparations were used immediately. Total protein concentration was measured using the Pierce BCA Protein Assay Kit.

[0170] Synaptosomal uptake and high potassium-induced release assays were performed as described in Example 1. Uptake assays using 250 μL aliquots of synaptosomal suspension were transferred to pre-chilled 0.8 mL 96-well plates. For direct comparison with our previous studies, 5 μL of test compound solution (0.5 mM; final concentration: 10 μM) was added to each well and incubated at 0° C. or 37° C. After 10, 20, or 30 min, samples were chilled on ice, immediately sedimented (2,500 g for 15 min at 4° C.) and washed with Buffer S (0.5 mL, ×2). The resulting pellet was resuspended in 200 μL of 60% ACN containing 5 μM GABA-d6 and stored at −80° C. until analysis. Potassium-induced release assays using 500 μL aliquots of synaptosomal suspension were transferred to pre-chilled microcentrifuge tubes. 2.5 μL of GABA-d6 in Buffer KRP was added to each well and incubated at 0° C. or 37° C. After 10, 20, or 30 min, samples were chilled on ice, immediately sedimented (2,500 g for 15 min at 4° C.) and washed with Buffer S (0.5 mL, ×2). The resulting pellet was resuspended in 200 μL of 60% ACN containing 5 μM GABA-d6 and stored at −80° C. until analysis. L of test compound solution (20 mM; final concentration: 100 μM) was added to each tube, incubated for 15 min at 37° C., briefly cooled on ice, then immediately precipitated (8,000 g for 4 min at 4° C.), washed with buffer KRP, and subsequently centrifuged twice. The resulting pellet was resuspended in 500 μL of buffer KRP or buffer K-KRP, incubated for 5, 10 or 15 min at 37° C., precipitated (8,000 g for 4 min at 4° C.), and washed with buffer KRP. The resulting pellet was resuspended in 400 μL of 60% ACN containing 2.5 μM GABA-d6 as an internal standard and stored at −80° C. until analysis.

[0171] Pharmacokinetics. Thirty-nine 2-3 month old C57BL / 6 male mice (Jackson Laboratory Cat. No. 000664) were administered a single IP injection (100 mg / kg) of R-4APA (n=18), S-4APA (n=18), or vehicle (n=3). At each time point (10 min, 30 min, 1 h, 2 h, 4 h, 6 h for test compound, 10 min for vehicle), mice were deeply anesthetized with isoflurane, blood was collected by cardiac puncture, allowed to clot on ice, and then perfused with cold PBS. Whole brains were rapidly dissected and half frozen at -80°C until homogenized in ice-cold PBS (pH 7.4) using a probe ultrasonic homogenizer (Branson Sonifier 450, power: 5, cycle: 30%, time: 10 sec) on ice. Lysates were sedimented (2,500 g for 15 min at 4° C.) and the supernatants were assayed using the Pierce BCA Protein Assay Kit (23225). Two or three 10 μL aliquots of homogenates were transferred to a 96-well plate and extracted with 190 μL of 60% acetonitrile in water containing 10 μM GABA-d6 as an internal standard for stable isotope dilution assays of endogenous GABA and 4APA enantiomers. L-Glu-d5 was used as an internal standard for assay glutamate exactly as previously described by the inventors. An aliquot of 40 μL of the extract was then diluted with 120 μL of acetonitrile and prepared for LC-MS / MS analysis. Brain and serum half-lives were calculated using the “PKNCA” package for R.

[0172] LC-MS / MS. LC-MS / MS HILIC analysis was performed using an Agilent 6470 Triple Quadrupole LC / MS System equipped with an Agilent 1290 Infinity II LC module. All samples were filtered through a Multiscreen Solvinert 0.45 μm PTFE filter plate into a polypropylene 0.5 mL 96-well plate. 2.5 μL was injected onto an Acquity UPLC BEH Amide column (2.1 × 50 mm, 1.7 μm particle size, Waters, part no. 186004800) equipped with an Acquity UPLC In-Line Filter (Waters, part no. 205000343) at 40 °C. A gradient elution protocol (flow rate of 0.6 mL / min) was developed to isolate the 4APA peak from the two isomeric compounds in the brain tissue homogenate. It consisted of buffer A (5 mM ammonium formate, 5 mM formic acid in water, pH 3.6) and buffer B (5 mM ammonium formate, 5 mM formic acid in 95:5 (v / v) acetonitrile-water) and a linear gradient of 5% to 30% A from 0.0 to 2.5 min, held at 40% A from 2.51 to 3.0 min, and held at 5% A from 3.01 to 3.5 min. The mass spectrometer was operated in multiple reaction monitoring (MRM) positive mode with the capillary voltage set at 3.5 kV, the nebulizer gas held at 250 °C, and the superheated sheet gas held at 300 °C. Results were corrected for isotopically labeled internal standards.

[0173] LC-MS / MS analysis, chiral conditions. LC-MS / MS chiral analysis was performed using an Agilent 6470 Triple Quadrupole LC / MS System equipped with an Agilent 1290 Infinity II LC module. Prior to analysis, all samples were filtered through a Multiscreen Solvinert 0.45 μm PTFE filter plate into a polypropylene 0.5 mL 96-well plate. 1.0 μL of sample was injected onto a CROWNPAK CR-I(+) column (3.0 × 150 mm, 5 μm particle size, Daicel, part no. 53784) equipped with an Acquity UPLC In-Line Filter (Waters, part no. 205000343) and thermostated at 20 °C. Samples were diluted in 0.4 mL portions with Buffer C (96:4 ACN / water v / v, 0.1% TFA; parameters were varied in optimization experiments). -1 The mass spectrometer was operated in multiple reaction monitoring (MRM) positive mode with the capillary voltage set at 3.5 kV, the nebulizer gas held at 250 °C, and the heated sheet gas held at 300 °C.

[0174] Receptor function and binding assays. All receptor assays were performed exactly as described in Example 1. All GABA A Functional assays of NMDA (GluN2A-GluN2D) and AMPA (GluA2) receptor subunits were performed by SB Drug Discovery as part of their CNS discovery panel using FLIPR technology. All compounds were tested in triplicate at seven concentrations and EC50 / IC50 were determined, where applicable. Functional GABA B The assay uses human GABA B In RBL cells expressing the Ca(B1 / B2) receptor, 2+ Dependent fluorescence quantification was performed by Eurofins Discovery (Cerep). All compounds were tested in triplicate at a single concentration of 100 μM. Nonspecific AMPA, kainate, and NMDA binding assays were performed on rat cerebral cortical membranes and radiolabeled [3 H]AMPA, 3 H]kainic acid, and [ 3 H]CGP39653 was used by Eurofins Discovery (Cerep). All compounds were tested in triplicate at a single concentration of 100 μM. mGluR1, mGluR2, mGluR5, and GABA B Binding assays were performed by Eurofins Discovery. All compounds were tested in triplicate at a single concentration of 100 μM.

[0175] Mouse behavior. Exploratory behavioral testing was performed using 2-month-old C57Bl / 6 male mice exactly as previously described by the inventors (Example 1). First, based on our previous study, we evaluated the safety and tolerability of acute exposure to 4APA enantiomers in 22 mice by novel cage observation at 100, 300, or 900 mg / kg IP compared to vehicle (PBS) IP (n=3 or 4 mice per group, no sample calculations). Next, we evaluated 24 drug-naive mice using a battery of 23 measurements: neurological impairment in mice after 30 or 100 mg / kg IP (SHIRPA) (Rogers et al., 2001), automated activity chamber assessment, and hot plate acute latency compared to vehicle IP (n=4 or 5 mice per group). Exclusion criteria were not pre-determined, and no randomization was performed to assign study subjects.

[0176] Statistics. Statistical analysis and graphing were performed using GraphPad Prism (San Diego, CA). Data were analyzed by two-way analysis of variance (ANOVA) with α = 0.05. D'Agostino and Pearson normality tests indicated normally distributed data (P > 0.05). Ordinary two-way ANOVA used Sidak's multiple comparison test, and repeated measures two-way ANOVA used Tukey's multiple comparison test, as indicated below in the figure legends. No outliers (>3 SD from the mean) were identified and no data points were excluded.

[0177] result Both enantiomers of 4APA were first precisely evaluated for neurotransmitter-like properties in mouse brain synaptosomes according to the method of Example 1. Uptake experiments revealed that both enantiomers of 4APA were transported into mouse brain synaptosomes, albeit at different rates. By 30 min at 37° C., the (R)-4APA synaptosomal concentration averaged 9.3±0.6 nmol / mg protein (n=3), whereas the (S)-4APA synaptosomal concentration was only 22.8±0.8% of (R)-4APA (P<0.0001) and the concentration of rac-4APA was 78.5±3.8% of (R)-4APA (P<0.0001) (FIG. 18). After preincubation with compound or vehicle, synaptosomes were incubated with 5 mM or 40 mM K + Membrane depolarization was induced by incubation for 15 min in a buffer containing 40 mM K. Under these conditions, synaptosomes preincubated with vehicle contained 9.5 ± 0.2 nmol GABA / mg protein (n = 3) and +Synaptosomes released 53.6±2.7% of their GABA with (R)-4APA, (S)-4APA, or rac-4APA (P<0.0001) (FIG. 18). Synaptosomes significantly decreased total GABA concentrations, varying from 3.8±0.5, 6.0±0.6, or 4.4±0.4 nmol / mg protein (n=3 per group, P<0.0001) after preincubation with (R)-4APA, (S)-4APA, or rac-4APA, respectively, and synaptosomal GABA retained after preincubation with 4APA enantiomers was significantly released by K+-induced membrane depolarization for all three compounds (n=3 per group, P<0.05) (FIG. 19). Synaptosomal Glu concentrations were not significantly altered by preincubation with rac-4APA. The synaptosomal concentrations of (R)-4APA or rac-4APA were also significantly reduced by K+-induced membrane depolarization: 55.3±6.8% for (R)-4APA (n=3, P<0.01) and 62.2±8.6% for rac-4APA (n=3, P<0.001). K+-induced membrane depolarization did not significantly reduce the synaptosomal concentration of (S)-4APA (FIG. 19B). Taken together, these data suggest that (R)-4APA and (S)-4APA had similar overall effects on synaptosomes, but the R enantiomer had faster uptake, displaced more GABA, and had a greater release after membrane depolarization.

[0178] We have shown that 2MeGlu, in contrast to L-Glu, is not decarboxylated in mouse synaptosomes or in vivo, and therefore 2MeGlu and 4APA are metabolically cleaved in the brain. Furthermore, oxidative deamination of 4APA to 4-oxopentanoic acid, the methyl analogue of succinic semialdehyde, does not occur in mouse brain synaptosomes incubated with rac-4APA. Thus, we determined the pharmacokinetics of (R)-4APA and (S)-4APA in serum and brain after a single 100 mg / kg intraperitoneal (IP) injection of the compounds (Figure 20). Vehicle-injected mice had background levels of 4APA of 3.5±1.1 μmol / L in serum and 4.4±0.9 pmol / mg protein in brain. Both enantiomers of 4APA were rapidly cleared from serum with a two-phase exponential decline, an initial rapid phase over 10-30 min, followed by a slower decline in concentration over the remaining 5.5 h. Both enantiomers of 4APA were also detectable in the brain by 10 min after IP injection and had reached stable concentrations by 1 h and up to 6 h. Taken together, these data indicate rapid clearance of both 4APA enantiomers from the blood and their retention, as well as apparent metabolic stability in the brain for up to 6 h.

[0179] Next, we investigated the pharmacokinetics of 4APA enantiomers against a broad panel of glutamate and GABA receptors in both binding and functional assays (summarized in Table 7). We purposely assayed 4APA enantiomers for activity against both glutamate and GABA receptors in the case of receptor class switching caused by insertion of a methyl group, as occurs with α-methyldopamine. (S)-4APA inhibits small amounts of GABA. A and GABA B 17-18 receptor isoforms, some of which have selective but weak agonists (GABA A α4β3δ, GABA A α5β2γ2 and GABA B B1 / B2) and antagonists (GABA A(R)-4APA showed GABA A It showed weak agonist activity at only α5β2γ2 receptors. Neither enantiomer of 4APA showed activity with glutamate receptors.

[0180] Stanford Behavioral and Functional Neuroscience Laboratory (SBFNL) researchers, blinded to the identity of the compounds being tested, performed extensive screening for safety and tolerability, followed by learning and memory testing, exactly like the behavioral screening for 2MeGlu. All behavioral assessments were performed with 2-month-old healthy drug-naive C57Bl / 6 male mice. Initial behavioral assessments after a single IP injection of compound or vehicle. To assess tolerability, mice were injected with a single dose of (R)-4APA or (S)-4APA (100, 300, or 900 mg / kg IP; n=3 per group) and then immediately assessed for survival over the next 10 days by novel cage observation (Figure 21). No mice died during the 10-day observation period. Distance traveled in the novel cage was significantly decreased in a dose- and time-dependent manner immediately after injection of either (R)-4APA or (S)-4APA, showing a significant reduction in response to novel / locomotor activity while maintaining vigilance and responsiveness, similar to what we observed with (R)-2MeGlu and (S)-2MeGlu (Figure 21A). The dose effects of the R and S enantiomers were not significantly different, but the duration of reduced movement in the novel cage test was longer for the R enantiomer. Only 300 and 900 mg / kg (R)-4APA-treated mice were significantly different from vehicle at 10 min post-injection (P<0.05 for both) (Figure 21B), and did not differ significantly from vehicle until 13 and 42 min post-injection, respectively.

[0181] We then used new groups of 2-month-old, drug-naive, wild-type C57Bl / 6 male mice to perform a behavioral test battery called SHIRPA (23-Measure Behavioral Screening of Neurological Dysfunction in Mice), activity chamber open field assessment, and then hot plate withdrawal exactly as previously described (n=4-5 per group) after a single IP injection of one of the two enantiomers or vehicle (n=4-5 per group). Again, there were no deaths in any of the treatment groups. Furthermore, at these doses, there were no significant differences between mice exposed to either dose of enantiomer and vehicle for any of the 23 SHIRPA measures, any of the activity chamber measures, or for any of the latencies to withdraw from the hot plate.

[0182] Enantiomers of 4APA have been previously synthesized, but conflicting absolute configurations have been reported (see Methods). For this reason, we directly determined the absolute configuration of the 4APA enantiomers used here. We recognize that there are no data regarding the enantiomer-specific biological activity of 4APA. (R)-4APA and (S)-4APA entered the mouse brain after IP injection and achieved similar relatively constant brain concentrations 2-6 hours after injection, despite an exponential decline in serum concentrations over the same period. These results showed that each enantiomer of 4APA was similarly retained by the brain over this period, in contrast to results described for 400 mg / kg IP of racemic 4APA, but not shown by others (see Callery et al. 1982). This discrepancy is likely related to our more sensitive and more specific detection method of pmol / mg protein concentrations of 4APA enantiomers in mouse brain. Both enantiomers were taken up into mouse brain synaptic particles in a time- and temperature-dependent manner, consistent with in vivo data showing retention in the brain. However, mouse synaptosomal uptake of (R)-APA was 4-5 times faster than that of (S)-4APA, whereas uptake of racemic 4APA was intermediate between the two enantiomers.

[0183] Upon incorporation into synaptosomes, (S)-4APA displaced approximately 30% of endogenous GABA, whereas (R)-4APA and racemic 4APA each displaced approximately 55% of endogenous GABA. The intrasynaptosomal concentrations of R and racemic 4APA were approximately twice that of the S enantiomers, and approximately 50%-60% of all four compounds (endogenous GABA, (R)-APA, (S)-4APA, and rac-4APA) were released by high concentrations of potassium ions. Taken together, these data support a model in which each enantiomer of 4APA crosses the blood-brain barrier, is taken up by GABAergic terminals, and is incorporated into synaptic vesicles where it partially replaces endogenous GABA, but (R)-APA is taken up more rapidly and achieves higher synaptosomal concentrations than (S)-4APA.

[0184] The rationale for including both GABAergic and glutamatergic receptors in our study was the observation that α-methyldopamine switches receptor class and interacts with noradrenergic receptors. We are not aware of any molecular modeling data that explored the potential effect of methyl substitutions in GABA to form 4APA on receptor binding. (S)-4APA had limited activity, and (R)-4APA had weak activity at only one of a broad panel of GABA and glutamate receptors. Taken together, these data support (R)-4APA as a GABAergic pseudoneurotransmitter, meaning that it is stored and released like a neurotransmitter, but has minimal activity at the receptor. We are not aware of any other GABAergic pseudoneurotransmitters. Given that the enantiomers of 4APA selectively displaced GABA in mouse synaptosomes, we hypothesize that they are substrates for GABA transporters, e.g., GAT-1 and GAT-3, although their specificity and affinity for GABA versus other transporters will be the focus of future experiments.

[0185] Our investigations of mouse behavior showed that both enantiomers of 4APA were safe up to 900 mg / kg IP and had clear dose-dependent pharmacological effects on novel locomotion / exploration in young healthy mice. At the same dose, the enantiomers had similar overall effects on locomotion / exploration with similar developmental timing, but the effect of the R enantiomer lasted longer than the S. This action of the 4APA enantiomers may be useful in some clinical situations, such as induction for treatment or imaging sessions, but they also have diagnostic or therapeutic value due to their extended half-life in the brain and unique properties as pseudoneurotransmitters, as occurred with α-methyldopa and α-methyltryptophan. The enantiomers of 4APA have applications as molecular imaging agents for GABAergic neurons in the treatment of diseases that stem in part from an imbalance in excitatory versus inhibitory neurotransmission, including mood disorders, psychoses, Alzheimer's disease, and Parkinson's disease.

[0186] [Table 7]

[0187] Example 3 S-2MeGlu dose-dependently rescues motor function in vivo Balanced excitatory (E, primarily glutamatergic) and inhibitory (I, primarily GABAergic) neurotransmission, both at the individual neuron and network level, is critical for brain function and neuronal health. Experimental and observational data support EI imbalance as a mechanism of neurodegeneration in Alzheimer's disease (AD) and Parkinson's disease (PD), most of which show increased E neurotransmission in the aged human brain and in the cerebrum of transgenic mouse models of AD. Indeed, one of the few FDA-approved treatments for AD is memantine, a noncompetitive antagonist for a specific subclass of ionotropic glutamate receptors. Furthermore, several groups are developing new pharmacological tools to restore EI balance in PD, focusing mainly on allosteric modulators of the metabotropic glutamate receptor subclass. These agents have activity in rodent models of PD with some evidence of neuroprotection, presumably by suppressing dysregulated excitatory inputs, and in the non-human primate 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model as an adjunct to dopamine replacement therapy.

[0188] Despite these impressive benefits, receptor-specific agents have inherent drawbacks. There are dozens of glutamate receptors that make it difficult to identify the most effective receptor subclass to target. Receptor expression is highly adaptable to specific targeting leading to decreased efficacy over time. Memantine is the only approved drug in its class. And this approach ignores the potential contribution of GABAergic neurotransmission. We have invented a group of small molecules that are the first glutamatergic or GABAergic pseudoneurotransmitters. Pseudoneurotransmitters are treated like endogenous or "true" neurotransmitters, including replacement of endogenous neurotransmitters in synaptic vesicles, but when released, pseudoneurotransmitters do not activate receptors. Our novel compounds offer a unique mode of action that rebalances EI neurotransmission in AD and PD, as well as other brain diseases, by altering neurotransmitter metabolism rather than targeting specific receptors.

[0189] The inventors created the first glutamatergic pseudoneurotransmitter (S-2-methylglutamate or S-2MeGlu) and the first GABAergic pseudoneurotransmitter (R-4 aminopentanomic acid (4APA) and S-4APA, the two enantiomers of which have different activity profiles). Others have been highly clinically successful by substituting the methyl group at the 2-position on the amino acid precursors of neurotransmitters, for example on L-dihydroxyphenylalanine to create aldomet, once a mainstay for controlling hypertension and still used in gestational hypertension, and on L-tryptophan to generate pseudoneurotransmitters used as neuroimaging agents for the serotonergic system in the human brain.

[0190] The data summarized below show that S-2MeGlu dose-dependently rescues motor function in two different mouse models of PD and cognitive improvement in a mouse model of AD, and that R-4APA rescues motor function in a transgenic mouse model of PD.

[0191] MPTP model of PD. Five groups of mice were treated with MPTP IP at 40 mg / kg / d on days 1 and 2, and two concentrations of the two test drugs IP from days -5 to 14 (Figure 22). One group received vehicle, two groups received S-2MeGlu at 5 or 50 mg / kg / d, and two groups received R-4APA at 5 or 50 mg / kg / d. MPTP mice significantly lost weight on days 3 and 4 compared to mice that did not receive MPTP (P<0.01). A high-precision fine motor kinematic protocol quantifies over 100 gait and balance indices and combines them into an overall kinematic score. Higher scores indicate greater impairment. After unblinding, S-2MeGlu at 50 mg / kg / d, but not R-4APA, significantly rescued motor deficits from MPTP. Mice were sacrificed on day 15, and striatal dopamine and its major metabolites were quantified by HPLC with electrochemical detection. Compared to the vehicle / vehicle group, all MPTP groups had approximately 70% reduction in striatal dopamine (P<0.0001 for each), but there were no significant differences between the MPTP / vehicle and MPTP / test drug groups. These data show S-2MeGlu dose-dependent rescue of MPTP-induced motor deficits without alteration of dopaminergic damage.

[0192] Transgenic α-synuclein mouse model. Line 61 mice overexpress human α-synuclein under the control of the mouse Thy-1 promoter. The transgene is X-linked, so females have variable transgene expression. For this reason, we focused on male mice. Motor function of Line 61 mice was measured using a tapered beam with video recording and scored as either (i) completely traversing the beam in less than 120 seconds, or (ii) falling off the beam or not completing the task in 120 seconds. Wild-type (WT) mice had significantly better motor performance (about 85% completely traversed the beam in less than 120 seconds) than Line 61 mice (not shown). As above, S-2MeGlu or R-4APA were administered for 7 days prior to testing (Figure 23). There were no changes in body weight or mortality. Categorical data from the tapered beam task were unblinded and analyzed by chi-square test (P<0.005). Line 61 mice treated with high dose S-2MeGlu or either dose of R-4APA improved motor function similarly to WT mice. There was no significant immunohistochemical change in α-synuclein accumulation in the brains of Line 61 mice treated with S-2MeGlu or R-4APA compared to vehicle. These results indicate a similar S-2MeGlu dose-dependent rescue of motor function in Line 61 mice as observed in the MPTP model. Unlike the MPTP model, a similar improvement in motor function was observed with both doses of R-4APA in Line 61 mice.

[0193] Transgenic Aβ model of AD. Cerebral Aβ accumulation is a core feature of AD. Because memantine, a glutamate receptor subtype antagonist, is an approved treatment for people with AD, we tested whether our pseudoglutamatergic neurotransmitter could be therapeutic in a transgenic model of AD. Four-month-old line 41 male mice were treated with S-2MeGlu at 10 mg / kg / d IP for 6 weeks and behavior was tested using activity chambers, Y-maze, novel object and novel place recognition, Morris water maze, and fear conditioning. There were no differences in body weight and mortality during the 6-week experiment. After unblinding, only S-2MeGlu rescued performance in the Y-maze (P<0.05, FIG. 24). There was no change in Aβ accumulation by immunohistochemistry in line 41 mice treated with S-2MeGlu. These data suggest that S-2MeGlu dose-dependently improves working memory in people with AD.

[0194] Neurodegeneration. We employed standard techniques of ex vivo experiments to determine the efficacy of 2MeGlu, 2MeGln, and 4APA to prevent neurodegeneration. Mouse hippocampal slice cultures were prepared and then exposed to one of the three test compounds at 5 or 50 μM for 1 hour. The medium was then changed to contain either 2 or 5 μM canicic acid (KA) for 24 hours. KA causes dose-dependent neurodegeneration in hippocampal neurons by activating its receptor and inducing excessive excitatory neurotransmission that is completely blocked by the ionotropic glutamate receptor subtype NMDA antagonist, memantine. After 24 hours, the amount of neurodegeneration was assayed using propidium iodide staining. Increasing doses of KA resulted in greater neurodegeneration at 5 μM than at 2 μM.

[0195] At the lower dose of KA, the higher dose of 2MeGlu or 2MeGln (50 μM) substantially reduced neurodegeneration by about half (FIG. 25). Neither dose of 2MeGlu or 2MeGln was neuroprotective at the higher dose of KA. 4APA was not neuroprotective in this model at either 5 or 50 μM. These data are important because they demonstrate a dose-dependent prevention of neurodegeneration from excessive excitatory neurotransmission by the pseudoglutamatergic neurotransmitter, 2MeGlu, and metabolically linked 2MeGln, but not by the pseudoGABAergic neurotransmitter, 4APA. In addition, this data is important because it provides an initial estimate of the effective concentration needed to block neurodegeneration. Pharmacokinetic studies in animal models will determine the doses needed to achieve effective concentrations in the brain, followed by clinical trials to establish safety and determine efficacy in people with Parkinson's disease, Alzheimer's disease, and other neurological diseases thought to result from an imbalance of excitatory and inhibitory neurotransmission.

[0196] Example 4 Imaging Four adult mice (M1-M4) were injected with radiolabeled 2MeGlu with 2.5 mg of non-radioactive 2MeGlu (M1) or without a cold spike (M2-M4) and then imaged by PET. 11 C-2MeGlu showed a rapid rise in brain radioactivity (3% ID / g), most of which was cleared within the first 10 min and is likely associated with labeled compound in the blood. Longer time points showed greater apparent brain retention in non-spiked injections, with approximately 0.5% of the injected dose retained in the whole brain for up to 40 min after injection. These results reflect rapid delivery of the radiotracer to the brain, followed by slower clearance over time.

[0197] The foregoing examples merely illustrate the principles of the present invention. It will be appreciated that those skilled in the art can devise various configurations that embody the principles of the present invention and are within the spirit and scope thereof, although not expressly described or shown herein. Furthermore, all examples and conditional language recited herein are intended primarily to aid the reader in understanding the principles of the present invention and the concepts contributed by the inventors to advance the art, and should not be construed as limitations to such specifically recited examples and conditions. Furthermore, all descriptions herein reciting the principles, aspects, and embodiments of the present invention, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, such equivalents are intended to include both currently known equivalents and equivalents developed in the future, i.e., any developed elements that perform the same function, regardless of structure. Thus, the scope of the present invention is not intended to be limited to the exemplary embodiments shown and described herein. Rather, the scope and spirit of the present invention is embodied by the appended claims.

[0198] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of and priority to U.S. Provisional Patent Application No. 63 / 170,773, filed April 5, 2021, the entire disclosure of which is incorporated herein by reference in its entirety.

Claims

1. 1. An agent that provides enantioselective metabolic control in the GABA shunt or glutamate-glutamine cycle for use in a method of altering the balance of excitatory to inhibitory neurotransmission, comprising: The method comprises administering an effective dose of the agent. Drugs.

2. The method of claim 1, wherein the agent is an enantiomer of 2-methyl-glutamate (2-MeGlu).

3. The method of claim 1, wherein the agent is an enantiomer of 2-methyl-glutamine (2-MeGln).

4. 2. The method of claim 1, wherein the agent is enantiomerically pure (S)-2-MeGlu or (R)-2-MeGlu.

5. The drug of claim 1, wherein the drug is a pseudoneurotransmitter that reduces glutamatergic neuronal activity.

6. The drug of claim 1, wherein the drug is a pseudoneurotransmitter that reduces GABAergic neuronal activity.

7. The medicament according to any one of claims 1 to 6, wherein the administration is provided in vivo to an individual in need thereof.

8. The method of claim 7, wherein the individual is suffering from Parkinson's disease.

9. The method of claim 7, wherein the individual is suffering from Alzheimer's disease.

10. The drug described in claim 7, wherein the individual is suffering from Huntington's disease.

11. The drug described in claim 7, wherein the individual suffers from epilepsy.

12. The drug described in claim 7, wherein the individual is suffering from amyotrophic lateral sclerosis (ALS).

13. The method of claim 7, wherein the compound is (S)-2-MeGlu or (R)-2-MeGlu.

14. 1. An agent for use in a method for molecular imaging of glutamate or glutamine producing and / or transporting cells in an individual, comprising: The method comprises: administering an effective dose of a detectably labeled enantiomer of 2-methyl-glutamate or 2-methyl-glutamine; detecting the presence of the labeled enantiomer in said individual; A drug comprising:

15. The method of claim 14, wherein the enantiomer is the S-enantiomer or the R-enantiomer.

16. The agent according to claim 14 or 15, wherein the label is an imaging label for positron emission tomography.

17. The label is １８ F. １１ C. １５ O or １３ The drug described in claim 16, which is N.

18. The method of claim 14 or 15, wherein the individual is suspected of having cancer.

19. 7. A pharma- ceutically acceptable formulation for use as a medicament according to any one of claims 1 to 6, comprising an effective dose of said agent providing enantioselective metabolic regulation in the GABA shunt or glutamate-glutamine cycle, and a pharma- ceutically acceptable excipient.

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