Anna Maria Capelli

Identification and Characterization of Novel NMDA Receptor Antagonists Selective for NR2A- over NR2B-Containing Receptors

NR1/NR2A is a subtype of N-methyl-d-aspartate receptors (NMDARs), which are glutamate and glycine-gated Ca2+-permeable channels highly expressed in the central nervous system. A high-throughput screening (HTS) campaign using human osteosarcoma (U-2 OS) cells transiently transduced with NR1/NR2A NMDAR subunits, tested in a specifically designed fluorometric imaging plate reader (FLIPR)/Ca2+ assay, identified sulfonamide derivative series, exemplified by 3-chloro-4-fluoro-N-[(4-{[2-(phenylcarbonyl)hydrazino]carbonyl}phenyl)methyl]benzenesulfonamide (compound 1) and thiodiazole derivative N-(cyclohexylmethyl)-2-({5-[(phenylmethyl)amino]-1,3,4-thiadiazol-2-yl}thio)acetamide (compound 13) as novel NR1/NR2A receptor antagonists. Compounds 1 and 13 displayed submicromolar and micromolar potency at NR1/NR2A receptor, respectively, although they did not show activity at NR2B-containing receptor up to 50 μM concentration. Addition of 1 mM glycine, but not 1 mM l-glutamate, was able to surmount compound 1 and 13 inhibitory effects in FLIPR NR1/NR2A assay. However, compounds 1 and 13 displaced a glutamate site antagonist [3H]d,l-(E)-2-amino-4-propyl-5-phosphono-3-pentenoic acid ([3H]CGP 39653) to a greater extent than the glycine site antagonist [3H]3-[(E)-2-carboxy-2-phenylethenyl]-4,6-dichloro-1H-indole-2-carboxylic acid ([3H]MDL 105,519), in rat brain cortex binding assay. Results of FLIPR cell-based, electrophysiological, and biochemical binding assays suggest that compounds 1 and 13 are the prototypes of novel classes of NMDAR ligands, which to the best of our knowledge are the first selective antagonists at NR1/NR2A over NR1/NR2B receptor, and might constitute useful tools able to elucidate the relative role of the NR2A subunit in physiological and pathological conditions.

1,2,4-Triazolyl Azabicyclo[3.1.0]hexanes: A New Series of Potent and Selective Dopamine D3 Receptor Antagonists

The discovery of new highly potent and selective dopamine (DA) D(3) receptor antagonists has recently allowed the characterization of the DA D(3) receptor in a range of preclinical animal models of drug addiction. A novel series of 1,2,4-triazol-3-yl-azabicyclo[3.1.0]hexanes, members of which showed a high affinity and selectivity for the DA D(3) receptor and excellent pharmacokinetic profiles, is reported here. Members of a group of derivatives from this series showed good oral bioavailability and brain penetration and very high in vitro affinity and selectivity for the DA D(3) receptor, as well as high in vitro potency for antagonism at this receptor. Several members of this series also significantly attenuate the expression of conditioned place preference (CPP) to nicotine and cocaine.

Synthesis and pharmacological characterization of novel druglike corticotropin-releasing factor 1 antagonists.

To identify new CRF(1) receptor antagonists, an attempt to modify the bis-heterocycle moiety present in the top region of the dihydropyrrole[2,3]pyridine template was made following new pharmacophoric hypothesis on the CRF(1) receptor antagonists binding pocket. In particular, the 2-thiazole ring, present in the previous series of compounds, was replaced by more hydrophilic non aromatic heterocycles able to make appropriate H-bond interactions with amino acid residues Thr192 and Tyr195. This exploration, followed by an accurate analysis of the substitution of the pendant aryl ring, enabled to identify in vitro potent compounds showing excellent pharmacokinetics and outstanding in vivo activity in animal models of anxiety, both in rodents and primates.

Synthesis and pharmacological characterisation of 2,4-Dicarboxy-pyrroles as selective non-Competitive mGluR1 antagonists

Metabotropic glutamate receptors (mGluRs) are an unusual family of G-protein coupled receptor (GPCR), and are characterised by a large extracellular N-terminal domain that contains the glutamate binding site. We have identified a new class of non-competitive metabotropic glutamate receptor 1 (mGluR1) antagonists, 2,4-dicarboxy-pyrroles which are endowed with nanomolar potency. They interact within the 7 transmembrane (7TM) domain of the receptor and show antinociceptive properties when tested in a number of different animal models.

Stable expression and functional characterization of a human nicotinic acetylcholine receptor with α6β2 properties: discovery of selective antagonists

Despite growing evidence that inhibition of α6β2‐containing (α6β2*) nicotinic acetylcholine receptors (nAChRs) may be beneficial for the therapy of tobacco addiction, the lack of good sources of α6β2*‐nAChRs has delayed the discovery of α6β2‐selective antagonists. Our aim was to generate a cell line stably expressing functional nAChRs with α6β2 properties, to enable pharmacological characterization and the identification of novel α6β2‐selective antagonists.

In vitro and in vivo characterization of the novel GABAB receptor positive allosteric modulator, 2-{1-[2-(4-chlorophenyl)-5-methylpyrazolo[1,5-a]pyrimidin-7-yl]-2-piperidinyl}ethanol (CMPPE).

There is preclinical evidence supporting the finding that the GABA(B) receptor orthosteric agonist, baclofen, has significant effects on eating behavior suggesting the potential therapeutic application of this compound for the treatment of eating related disorders. However, the wide clinical use of baclofen might be limited by the appearance of sedative and motor impairment effects. The identification of positive allosteric modulators (PAMs) of GABA(B) receptors represents a novel therapeutic approach to reduce the centrally-mediated adverse effects typical of the GABA(B) receptor orthosteric agonist. In the present work, we report the in vitro profile of a novel chemical structure, 2-{1-[2-(4-chlorophenyl)-5-methylpyrazolo[1,5-a]pyrimidin-7-yl]-2-piperidinyl}ethanol (CMPPE) identified by screening the GSK compound collection. CMPPE potentiates GABA-stimulated [(35)S]GTPγS binding to membranes of human recombinant cell line and of rat brain cortex. GABA concentration-response curves (CRC) in the presence of fixed concentrations of CMPPE, in rat native tissue, revealed an increase of both the potency and maximal efficacy of GABA. A similar modulatory effect was observed in GABA(B) receptor-mediated activation of inwardly rectifying potassium channels in hippocampal neurons. CMPPE (30-100 mg/kg) and GS39783 (100 mg/kg) significantly decreased food consumption in rat without impairment on the animal locomotor activity. On the contrary, baclofen (2.5 mg/kg) decreased both food intake and motor performance. All together these findings confirm the role of GABA(B) system in controlling animal food intake and for the first time demonstrate that GABA(B) receptor PAMs may represent a novel pharmacological approach to treat eating disorders without unwanted sedative effects.

Exploration of the amine terminus in a novel series of 1,2,4-triazolo-3-yl-azabicyclo[3.1.0]hexanes as selective dopamine D3 receptor antagonists.

A novel series of 1,2,4-triazol-3-yl-azabicyclo[3.1.0]hexanes with high affinity and selectivity for the DA D(3) receptor and excellent pharmacokinetic profiles was recently reported. We also recently discussed the role of the linker associated with the triazole moiety. In this manuscript, we are reporting a detailed exploration of the region of the receptor interacting with the amine terminus of the scaffold wherein SAR and developability data associated with these novel templates was undertaken.

New fused benzazepine as selective D3 receptor antagonists. Synthesis and biological evaluation. Part one : [h]-fused tricyclic systems

The synthesis and SAR of a new series of potent and selective dopamine D(3) receptor antagonists is reported. The introduction of a tricyclic [h]-fused benzazepine moiety on the recently disclosed scaffold of 1,2,4-triazol-3-yl-thiopropyl-tetrahydrobenzazepines is reported. A full rat pharmacokinetic characterization is also reported.

Unbinding pathways from the glucocorticoid receptor shed light on the reduced sensitivity of glucocorticoid ligands to a naturally occurring, clinically relevant mutant receptor.

Glucocorticoids are endogenous steroid hormones that regulate essential biological functions, including metabolism, growth, and apoptosis. Glucocorticoids represent the most effective anti-inflammatory agents for the treatment of several inflammatory conditions. However, the clinical use of such drugs is hampered by severe side effects. Therefore, the development of novel glucocorticoid receptor (GR) modulators with an increased therapeutic index is impelling. Herein, using steered molecular dynamics (SMD) simulations, we provide a detailed picture of the unbinding process of three clinically relevant GR modulators from GR ligand binding domains. The SMD protocol described here can be used to prioritize the synthesis of structural analogues on the basis of their potentials of mean force and calculated unbinding energies. Moreover, our results are instrumental in explaining at atomic resolution the weakened ability of dexamethasone to activate the naturally occurring mutant I747M GR, which is implicated in rare familial glucocorticoid resistance, clinically characterized by glucocorticoid insensitivity.

Unbinding pathways of VEGFR2 inhibitors revealed by steered molecular dynamics.

A detailed atomistic description of the unbinding process of sorafenib and sunitinib, two known VEGFR2 inhibitors clinically used to treat renal cell carcinoma, was unraveled by using steered molecular dynamics (SMD) simulations. While sunitinib is a fast-dissociating binder, sorafenib exhibits quite a long residence time at this enzyme, which might impact its duration of action in vivo. In order to gain insights into the kinetically different behaviors of the two inhibitors, an SMD study was carried out, which involved a careful optimization of the force and velocity parameters. We were able to identify two different binding pathways for the two inhibitors, as sunitinib exited the ATP binding site from the cavity entrance without a rupture point while sorafenib moved opposite to the ATP binding site entrance. Furthermore, the calculated ΔGoff values clearly reflect on a qualitative level the distinct off-rates of the two inhibitors, thus suggesting that this protocol could be tried on other VEGFR2 ligands to assess its robustness and then used to rank structural analogues of these derivatives.