Pharmacological evaluation of E2730, a novel selective uncompetitive GAT1 inhibitor, on epileptiform activities in resected brain tissues from human focal cortical dysplasia ex vivo.

Focal cortical dysplasia (FCD) is an important etiology of focal epilepsy in children and adults. However, only a few preclinical models sufficiently reproduce the characteristic histopathologic features of FCD. To improve the success rate of clinical trials for antiseizure medications (ASMs) in patients with FCD, more human-relevant preclinical models are needed, and epileptic foci resected from patients are a powerful tool for this purpose. Here, we conducted ex vivo studies using epileptic foci resected from patients with FCD type II to evaluate the pharmacologic effects of the ASM candidate E2730, a selective uncompetitive inhibitor of γ-aminobutyric acid transporter 1. We used the same ex vivo assay system to assess carbamazepine (CBZ), an ASM often prescribed for focal epilepsy, as a reference. At the higher dose tested (200 µM), both E2730 and CBZ suppressed spontaneous epileptiform activities almost completely. At the lower dose (100 µM), CBZ reduced the area of brain tissue showing epileptiform activity, whereas E2730 significantly decreased the number of epileptiforms. These findings suggest that E2730-both as a single agent and in combination with CBZ-merits evaluation in clinical trials involving patients with FCD.

Nipecotic Acid Derivatives as Potent Agents against Neurodegeneration: A Preliminary Study.

Alzheimer's Disease (AD) is a common neurodegenerative disorder characterized by memory loss and cognitive impairment. Its pathology has not been fully clarified and therefore highly effective treatments have not been obtained yet. Almost all the current treatment options aim to alleviate only the symptoms and not to eliminate the disease itself. Acetylcholinesterase inhibitors are the main therapeutic agents against AD, whereas oxidative stress and inflammation have been found to be of great significance for the development and progression of neurodegeneration. In this work, ethyl nipecotate (ethyl-piperidine-3-carboxylate), a heterocyclic carboxylic acid derivative, which acts as a GABA reuptake inhibitor and has been used in research for diseases involving GABAergic neurotransmission dysfunction, was amidated with various carboxylic acids bearing antioxidant and/or anti-inflammatory properties (e.g., ferulic acid, sinapic acid, butylated hydroxycinnamic acid). Most of our compounds have significant antioxidant potency as lipid peroxidation inhibitors (IC50 as low as 20 µΜ), as oxidative protein glycation inhibitors (inhibition up to 57%), and act as DPPH reducing agents. Moreover, our compounds are moderate LOX inhibitors (up to 33% at 100 µΜ) and could reduce rat paw edema induced by carrageenan by up to 61%. Finally, some of them possessed inhibitory activity against acetylcholinesterase (IC50 as low as to 47 µΜ). Our results indicate that our compounds could have the potentiality for further optimization as multi-targeting agents directed against AD.

Structural basis of GABA reuptake inhibition.

γ-Aminobutyric acid (GABA) transporter 1 (GAT1)1 regulates neuronal excitation of the central nervous system by clearing the synaptic cleft of the inhibitory neurotransmitter GABA upon its release from synaptic vesicles. Elevating the levels of GABA in the synaptic cleft, by inhibiting GABA reuptake transporters, is an established strategy to treat neurological disorders, such as epilepsy2. Here we determined the cryo-electron microscopy structure of full-length, wild-type human GAT1 in complex with its clinically used inhibitor tiagabine3, with an ordered part of only 60 kDa. Our structure reveals that tiagabine locks GAT1 in the inward-open conformation, by blocking the intracellular gate of the GABA release pathway, and thus suppresses neurotransmitter uptake. Our results provide insights into the mixed-type inhibition of GAT1 by tiagabine, which is an important anticonvulsant medication. Its pharmacodynamic profile, confirmed by our experimental data, suggests initial binding of tiagabine to the substrate-binding site in the outward-open conformation, whereas our structure presents the drug stalling the transporter in the inward-open conformation, consistent with a two-step mechanism of inhibition4. The presented structure of GAT1 gives crucial insights into the biology and pharmacology of this important neurotransmitter transporter and provides blueprints for the rational design of neuromodulators, as well as moving the boundaries of what is considered possible in single-particle cryo-electron microscopy of challenging membrane proteins.

Nipecotic acid as potential lead molecule for the development of GABA uptake inhibitors; structural insights and design strategies.

Gamma-Aminobutyric Acid (GABA) inhibitory neurotransmitter departs an energetic role in brain signalling system. Levels of GABA in the brain influence human behaviour, diminishes in the degree of GABA can cause seizures, depression, Parkinson's. To put it plainly, it plays a basic part in the significant issues of mind. It is exceptionally important to cure the issues linked to GABA. Writing overview proposed that nipecotic acid is an intense GABA reuptake inhibitor. This scaffold is likewise present in one of the promoted anticonvulsant drugs 'Tiagabine'. Tiagabine is only drug in the market which works through this mechanism however the medication is regulated with one more prescription for the synergistic impact. Nipecotic acid has several disadvantages such as it can't cross the blood-brain barrier because of its hydrophilic and zwitterionic nature. To avoid this problem nipecotic acid scaffold hybrids with the different aromatic groups can enhance the physical (lipophilicity) as well as biological properties of the resultant compound. So, there is a dire requirement for compounds that work through this mechanism. Several medicinal chemists and researchers are already working in this field and developed outstanding newer molecules. This review article compiles these developed new hybrids along with design strategies, structure-activity relationship, and biological activity as well as in silico studies. This review also demonstrates the synthesis of nipecotic acid and the core mechanism through which nipecotic acid acts as a GABA reuptake inhibitor.

Development of tricyclic N-benzyl-4-hydroxybutanamide derivatives as inhibitors of GABA transporters mGAT1-4 with anticonvulsant, antinociceptive, and antidepressant activity.

γ-Aminobutyric acid (GABA) neurotransmission has a significant impact on the proper functioning of the central nervous system. Numerous studies have indicated that inhibitors of the GABA transporters mGAT1-4 offer a promising strategy for the treatment of several neurological disorders, including epilepsy, neuropathic pain, and depression. Following our previous results, herein, we report the synthesis, biological evaluation, and structure-activity relationship studies supported by molecular docking and molecular dynamics of a new series of N-benzyl-4-hydroxybutanamide derivatives regarding their inhibitory potency toward mGAT1-4. This study allowed us to identify compound 23a (N-benzyl-4-hydroxybutanamide bearing a dibenzocycloheptatriene moiety), a nonselective GAT inhibitor with a slight preference toward mGAT4 (pIC50 = 5.02 ± 0.11), and compound 24e (4-hydroxy-N-[(4-methylphenyl)-methyl]butanamide bearing a dibenzocycloheptadiene moiety) with relatively high inhibitory activity toward mGAT2 (pIC50 = 5.34 ± 0.09). In a set of in vivo experiments, compound 24e successively showed predominant anticonvulsant activity and antinociception in the formalin model of tonic pain. In contrast, compound 23a showed significant antidepressant-like properties in mice. These results were consistent with the available literature data, which indicates that, apart from seizure control, GABAergic neurotransmission is also involved in the pathophysiology of several psychiatric diseases, however alternative mechanisms underlying this action cannot be excluded. Finally, it is worth noting that the selected compounds showed unimpaired locomotor skills that have been indicated to give reliable results in behavioral assays.

GABAergic cortical network physiology in frontotemporal lobar degeneration.

The clinical syndromes caused by frontotemporal lobar degeneration are heterogeneous, including the behavioural variant frontotemporal dementia (bvFTD) and progressive supranuclear palsy. Although pathologically distinct, they share many behavioural, cognitive and physiological features, which may in part arise from common deficits of major neurotransmitters such as γ-aminobutyric acid (GABA). Here, we quantify the GABAergic impairment and its restoration with dynamic causal modelling of a double-blind placebo-controlled crossover pharmaco-magnetoencephalography study. We analysed 17 patients with bvFTD, 15 patients with progressive supranuclear palsy, and 20 healthy age- and gender-matched controls. In addition to neuropsychological assessment and structural MRI, participants undertook two magnetoencephalography sessions using a roving auditory oddball paradigm: once on placebo and once on 10 mg of the oral GABA reuptake inhibitor tiagabine. A subgroup underwent ultrahigh-field magnetic resonance spectroscopy measurement of GABA concentration, which was reduced among patients. We identified deficits in frontotemporal processing using conductance-based biophysical models of local and global neuronal networks. The clinical relevance of this physiological deficit is indicated by the correlation between top-down connectivity from frontal to temporal cortex and clinical measures of cognitive and behavioural change. A critical validation of the biophysical modelling approach was evidence from parametric empirical Bayes analysis that GABA levels in patients, measured by spectroscopy, were related to posterior estimates of patients' GABAergic synaptic connectivity. Further evidence for the role of GABA in frontotemporal lobar degeneration came from confirmation that the effects of tiagabine on local circuits depended not only on participant group, but also on individual baseline GABA levels. Specifically, the phasic inhibition of deep cortico-cortical pyramidal neurons following tiagabine, but not placebo, was a function of GABA concentration. The study provides proof-of-concept for the potential of dynamic causal modelling to elucidate mechanisms of human neurodegenerative disease, and explains the variation in response to candidate therapies among patients. The laminar- and neurotransmitter-specific features of the modelling framework, can be used to study other treatment approaches and disorders. In the context of frontotemporal lobar degeneration, we suggest that neurophysiological restoration in selected patients, by targeting neurotransmitter deficits, could be used to bridge between clinical and preclinical models of disease, and inform the personalized selection of drugs and stratification of patients for future clinical trials.

Development, Recent Achievements and Current Directions of Research into GABA Uptake Inhibitors.

Neurotransmitter γ-aminobutyric acid (GABA) plays a principal role in the regulation of mammalian central nervous system functions. GABA evoked neurotransmission is terminated by a rapid uptake via dependent plasma membrane GABA transporters (GATs) located in the cell membrane. Potent inhibitors of these GATs are of fundamental importance for elucidation of the physiological function of these targets. Over recent years, a wide range of new GAT1-selective and less common non-GAT1-selective inhibitors have been successfully developed. This review highlights development and recent significant achievements in the field of GABA reuptake inhibitors. Special attention is paid to their pharmacological roles, structure and subtype selectivity relationships.

Tiagabine-related status epilepticus: a case report and systematic literature review.

Tiagabine-related status epilepticus (SE) is an uncommon complication of tiagabine use. We aimed to detail the features and outcomes in a patient with tiagabine poisoning and review the relevant literature. We describe a case of tiagabine-related SE and literature review based on a 1995-2019 PubMed search. We report the case of a 30-year-old man with super-refractory SE after tiagabine poisoning. He fully recovered after 72 h of general anesthesia and was discharged from the ICU on day 16. A literature review showed distinct features among patients with tiagabine-related SE. Tiagabine side effects were characterized by non-convulsive SE after a slight increase in tiagabine dose and a rapid favorable evolution after benzodiazepine and early tiagabine withdrawal. Generalized convulsive SE was a complication of voluntary or involuntary tiagabine poisoning and was particularly refractory. Both presentations are characterized by a return to baseline after prompt and adequate management. Tiagabine-related SE electroclinical features vary according to the underlying pathophysiological mechanism and can be life threatening. Recovery is the rule after tiagabine withdrawal and SE management with progressive therapeutic escalation guided by response to prior anticonvulsant treatments.

N-Substituted Nipecotic Acids as (S)-SNAP-5114 Analogues with Modified Lipophilic Domains.

Potential mGAT4 inhibitors derived from the lead substance (S)-SNAP-5114 have been synthesized and characterized for their inhibitory potency. Variations from the parent compound included the substitution of one of its aromatic 4-methoxy and 4-methoxyphenyl groups, respectively, with a more polar moiety, including a carboxylic acid, alcohol, nitrile, carboxamide, sulfonamide, aldehyde or ketone function, or amino acid partial structures. Furthermore, it was investigated how the substitution of more than one of the aromatic 4-methoxy groups affects the potency and selectivity of the resulting compounds. Among the synthesized test substances (S)-1-{2-[(4-formylphenyl)bis(4-methoxyphenyl)-methoxy]ethyl}piperidine-3-carboxylic acid, that features a carbaldehyde function in place of one of the aromatic 4-methoxy moieties of (S)-SNAP-5114, was found to have a pIC50 value of 5.89±0.07, hence constituting a slightly more potent mGAT4 inhibitor than the parent substance while showing comparable subtype selectivity.

GABA-ergic Dynamics in Human Frontotemporal Networks Confirmed by Pharmaco-Magnetoencephalography.

To bridge the gap between preclinical cellular models of disease and in vivo imaging of human cognitive network dynamics, there is a pressing need for informative biophysical models. Here we assess dynamic causal models (DCM) of cortical network responses, as generative models of magnetoencephalographic observations during an auditory oddball roving paradigm in healthy adults. This paradigm induces robust perturbations that permeate frontotemporal networks, including an evoked 'mismatch negativity' response and transiently induced oscillations. Here, we probe GABAergic influences in the networks using double-blind placebo-controlled randomized-crossover administration of the GABA reuptake inhibitor, tiagabine (oral, 10 mg) in healthy older adults. We demonstrate the facility of conductance-based neural mass mean-field models, incorporating local synaptic connectivity, to investigate laminar-specific and GABAergic mechanisms of the auditory response. The neuronal model accurately recapitulated the observed magnetoencephalographic data. Using parametric empirical Bayes for optimal model inversion across both drug sessions, we identify the effect of tiagabine on GABAergic modulation of deep pyramidal and interneuronal cell populations. We found a transition of the main GABAergic drug effects from auditory cortex in standard trials to prefrontal cortex in deviant trials. The successful integration of pharmaco- magnetoencephalography with dynamic causal models of frontotemporal networks provides a potential platform on which to evaluate the effects of disease and pharmacological interventions.SIGNIFICANCE STATEMENT Understanding human brain function and developing new treatments require good models of brain function. We tested a detailed generative model of cortical microcircuits that accurately reproduced human magnetoencephalography, to quantify network dynamics and connectivity in frontotemporal cortex. This approach identified the effect of a test drug (GABA-reuptake inhibitor, tiagabine) on neuronal function (GABA-ergic dynamics), opening the way for psychopharmacological studies in health and disease with the mechanistic precision afforded by generative models of the brain.

Novel mouse GABA uptake inhibitors with enhanced inhibitory activity toward mGAT3/4 and their effect on pain threshold in mice.

γ-Aminobutyric acid (GABA) uptake transporters are membrane transport proteins that are involved in the pathophysiology of a number of neurological disorders. Some types of chronic pain appear to result from the dysfunction of the GABAergic system. The deficiency of mouse GAT1 transporter (mGAT1) abolishes the nociceptive response, which means that mGAT1 inhibition is an appropriate medical approach to achieve analgesia. The mGAT4 transporter is the second most abundant GAT subtype in the brain; however, its physiological role has not yet been fully understood in the central nervous system. In this study, we examined whether the combination of mGAT1 and mGAT3/mGAT4 inhibition in a single molecule might lead to potentially synergistic effects improving analgesic activity to relieve neuropathic pain. To study this hypothesis, new GABA uptake inhibitors were designed, synthesized, and evaluated in terms of their activity and subtype selectivity for mGAT1-4. Among new functionalized amino acid derivatives of serine and GABA analogs, compounds with preferential mGAT3/4 inhibitory activity were discovered. Two selected hits (19b and 31c) were subjected to in vivo tests. We found a statistically significant antiallodynic activity in the von Frey test in diabetic and oxaliplatin-induced neuropathic pain model. The novel compounds (4-hydroxybutanoic, 4-hydroxypentanoic, and 4-aminobutanoic acid derivatives and serine analogs) provide new insights into the structure-activity relationship of mGAT3/mGAT4 inhibitors and indicate a new direction in the search for potential treatment of neuropathic pain of various origin.

Application of the concept of oxime library screening by mass spectrometry (MS) binding assays to pyrrolidine-3-carboxylic acid derivatives as potential inhibitors of γ-aminobutyric acid transporter 1 (GAT1).

In the present study, the concept of oxime library screening by MS Binding Assays was successfully extended to N-substituted lipophilic pyrrolidine-3-carboxylic acid derivatives in the pursuit of varying the amino acid motif in order to identify new inhibitors for GAT1 and to broaden structure-activity-relationships for this target, the most abundant GABA transporter in the central nervous system. For the screening, 28 different oxime sub-libraries were employed that were generated by simple condensation reaction of an excess of pyrrolidine-3-carboxylic acid derivatives carrying a hydroxylamine functionality with various sub-libraries each assembled of eight aldehydes with broadly varying chemical structures and functionalities. The compounds responsible for the activity of an oxime sub-library were identified by deconvolution experiments performed by employing single oximes. Binding affinities of the oxime hits were confirmed in full-scale competitive MS Binding Assays. Thereby, oxime derivatives with a 1,1'-biphenyl moiety were found as the first inhibitors of mGAT1 comprising a pyrrolidine-3-carboxylic acid motif with affinities in the submicromolar range.

Synthesis and biological evaluation of novel N-substituted nipecotic acid derivatives with a cis-alkene spacer as GABA uptake inhibitors.

To discover new, potent, and selective inhibitors for the murine gamma-aminobutyric acid transporter 4 (mGAT4), the structure-activity relationship (SAR) study of a new cis-alkene analog family based on DDPM-1457 [(S)-2], which previously showed promising inhibitory potency at and subtype selectivity for mGAT4, was conducted. To uncover the importance of the differences between the trans- and the cis-alkene moiety in the spacer, the present publication describes the synthesis of the new compounds via catalytic hydrogenation with Lindlar's catalyst. The biological results collected by the SAR study revealed that analog rac-7j characterized by a four-instead of a three-carbon atom spacer with a cis double bond applying to the majority of the studied compounds displays a surprisingly high potency at mGAT1 (pIC50 = 6.00 ±â€¯0.04) and at the same time a reasonable potency at mGAT4 (pIC50 = 4.82).

MS-Based Screening of 5-Substituted Nipecotic Acid Derived Hydrazone Libraries as Ligands of the GABA Transporter†1.

A screening of compound libraries based on nipecotic acid derivatives with lipophilic residues attached to the scarcely explored 5-position of the core structure was used for the search of new inhibitors of the γ-aminobutyric acid (GABA) transporter 1 (mGAT1). The generated compound libraries, which were based on hydrazone chemistry commonly used in dynamic combinatorial chemistry but rendered pseudostatic, were screened for their binding affinities toward mGAT1 by means of MS Binding Assays. With nipecotic acid derived hydrazone rac-16 h [rac-(3R,5S)-{5-[(E)-2-{[5-(2-phenylethynyl)thiophen-2-yl]methylidene}hydrazin-1-yl]piperidine-3-carboxylic acid}-sodium chloride (1/2)], one hit was found and evaluated displaying sub-micromolar potency (pKi =6.62±0.04) and a noncompetitive interaction mode at mGAT1. By bearing a 5-(2-phenylethynyl)thiophen-2-yl residue attached to the 5-position of nipecotic acid via a three-atom spacer, compound rac-16 h contains a structural moiety so far unprecedented for these kinds of bioactive molecules, and complements novel 5-substituted nipecotic acid derived ligands of mGAT1 revealed in a recently published screening campaign. This new class of ligands, with an inhibition mode distinct from that of benchmark mGAT1 inhibitors, could serve as research tools for investigations of mGAT1-mediated GABA transport.

Studies on the Activity of Selected Highly Lipophilic Compounds toward hGAT1 Inhibition. Part II.

In this paper, we describe the latest results involving molecular modeling and pharmacodynamic studies of the selected highly lipophilic compounds acting by human GABA transporter 1 (hGAT1) inhibition. The chemical interaction of 17 GABA analogues with a model of hGAT1 is described using the molecular docking method. The biological role of GAT1 is related to the regulation of GABA level in the central nervous system and GAT1 inhibition plays an important role in the control of seizure threshold. To confirm that GAT1 can be also a molecular target for drugs used to treat other neurological and psychiatric diseases (e.g., pain and anxiety), in the in vivo part of this study, potential antinociceptive and anxiolytic-like properties of tiagabine, a selective GAT1 inhibitor, are described.

Generation and screening of pseudostatic hydrazone libraries derived from 5-substituted nipecotic acid derivatives at the GABA transporter mGAT4.

The γ-aminobutyric acid (GABA) transporter mGAT4 represents a promising drug target for the treatment of epilepsy and other neurological disorders; however, the lack of highly potent and selective inhibitors for mGAT4 still retards its pharmacological elucidation. Herein, the generation and screening of pseudostatic combinatorial hydrazone libraries at the murine GABA transporter mGAT4 for the search of novel GABA uptake inhibitors is described. The hydrazone libraries contained more than 1100 compounds derived from nipecotic acid derivatives substituted at the 5-position instead, as common, at the 1-position of the core structure. Two hits were found and evaluated, which display potencies in the lower micromolar range at mGAT4 and its human equivalent hGAT3. These compounds possess a lipophilic moiety derived from a biphenyl residue attached to the 5-position of the hydrophilic nipecotic acid moiety via a three-atom spacer. Thus, the novel structures with potencies close to that of the bench mark mGAT4 inhibitor (S)-SNAP-5114 add new insights into the structure-activity relationship of mGAT4 inhibitors and could provide a promising starting point for the development of new mGAT4 inhibitors with even higher potencies.

Identification of Pyrrolidine-3-acetic Acid Derived Oximes as Potent Inhibitors of γ-Aminobutyric Acid Transporter†1 through Library Screening with MS Binding Assays.

In this study, pyrrolidine-3-acetic acid derived oxime libraries were applied to the concept of library screening by MS Binding Assays, as a powerful technique to reveal new potent murine γ-aminobutyric acid transporter subtype (mGAT1) inhibitors. Library generation was accomplished by condensation of an excess of pyrrolidine-3-acetic acid bearing a hydroxylamine unit with various libraries, each composed of eight different aldehydes. The oxime libraries have been screened by means of competitive MS Binding Assays and, as a consequence, the most active libraries were further investigated through deconvolution experiments to identify single oximes responsible for the observed activity on the target mGAT1. All identified hits were finally resynthesized to characterize them with respect to their binding affinities, and a set of new potent inhibitors with the pyrrolidine-3-acetic acid motif were found, of which the most potent oxime, possessing a 2',4'-dichlorobiphenyl residue, displayed a binding affinity in the low nanomolar range (pKi =7.87±0.01).

Synthesis and biological evaluation of novel N-substituted nipecotic acid derivatives with a trans-alkene spacer as potent GABA uptake inhibitors.

Our study presents the synthesis and structure-activity relationship (SAR) of novel N-substituted nipecotic acid derivatives closely related to DDPM-1457 [(S)-2a], a chemically stable analog of (S)-SNAP-5114 (1), in the pursuit of finding new and potent mGAT4 selective inhibitors. Iminium ion chemistry served as key step for the preparation of the desired, new N-substituted nipecotic acid derivatives containing a variety of different heterocycles attached to the nipecotic acid moiety via a trans-alkene spacer. The target compounds were characterized with regard to their potency at and subtype selectivity for the GABA transporters mGAT1-mGAT4.

Docking and pharmacodynamic studies on hGAT1 inhibition activity in the presence of selected neuronal and astrocytic inhibitors. Part I.

Inhibition of 4-aminobutanoic acid (GABA) uptake is a strategy for enhancing GABA transmission. The utility of this approach is demonstrated by the successful development of such agents for the treatment of epilepsy and pain. Existing reports on acute brain slice preparations indicate the intersecting of complementary channels and receptors sets between astrocytes and neurons cells. Thorough analysis of astroglial cells by means of molecular and functional studies demonstrated their active modulatory role in intercellular communication. The chemical interactions between sixteen GABA analogues and isoform of hGAT1 is outlined in the light of molecular docking results. In the in vivo part antinociceptive properties of racemic nipecotic acid, its R and S enantiomers and isonipecotic acid, each administered intraperitoneally at 3 fixed doses (10, 30 and 100 mg/kg), were assessed in a thermally-induced acute pain model i.e. the mouse hot plate test. Docking analyses provided complex binding energies, specific h-bond components, and h-bond properties, such as energies, distances and angles. In vivo tests revealed statistically significant antinociceptive properties of isonipecotic acid (10 and 30 mg/kg), R-nipecotic acid (30 and 100 mg/kg) and S-nipecotic acid (100 mg/kg) in mice. The docking data endorse the hypothesis of correlation between the strength of their chemical interactions with hGAT1 and analgesic action of studied compounds.

Design and synthesis of cyclopropane-based conformationally restricted GABA analogues as selective inhibitors for betaine/GABA transporter 1.

We previously designed and synthesized a series of cyclopropane-based conformationally restricted analogues of γ-aminobutyric acid (GABA). The study demonstrated that the critical conformation of the analogues that selectively active to betaine/GABA transporter 1 (BGT1) subtype is the trans-syn-form, in which the amino and carboxyl groups are in trans-configuration and the cyclopropane ring and the carboxyl group are in syn-arrangement. In this study, we designed and synthesized cyclopropane-based GABA analogues, which were conformationally restricted in the trans-syn-form by cyclopropylic strain based on the stereochemistry of the carbon adjacent to cyclopropane. Their conformation was confirmed as the syn-form by calculations and NMR studies, and their pharmacological evaluation clarified that compounds 11a and 11d had the BGT1 selectivity, although their inhibitory effects were insufficient.