Identification of RC-33 as a potent and selective σ1 receptor agonist potentiating NGF-induced neurite outgrowth in PC12 cells. Part 2: g-scale synthesis, physicochemical characterization and in vitro metabolic stability

Novel S1R agonists counteracting NMDA excitotoxicity and oxidative stress: A step forward in the discovery of neuroprotective agents

Sigma-1 receptor (S1R) has been considered a promising therapeutic target for several neurodegenerative diseases and S1R agonists have shown neuroprotective activity against glutamate excitotoxicity and oxidative stress. Starting from a previously identified low nanomolar S1R agonist, in this work we prepared and tested novel benzylpiperidine/benzylpiperazine-based compounds designed by applying a ring opening strategy. Among them, 4-benzyl-1-(2-phenoxyethyl)piperidine 6b (S1R Ki = 0.93 nM) and 4-benzyl-1-(3-phenoxypropyl)piperidine 8b (S1R Ki = 1.1 nM) emerged as high affinity S1R ligands and showed selectivity over S2R and N-methyl-d-aspartate receptor (NMDAR). Candidate compounds behaved as potent S1R agonists being able to enhance the neurite outgrowth induced by nerve growth factor (NGF) in PC12 cell lines. In SH-SY5Y neuroblastoma cell lines they exhibited a neuroprotective effect against rotenone- and NMDA-mediated toxic insults. The neuroprotective activity of 6b and 8b was reverted by co-treatment with an S1R antagonist, PB212. Compounds 6b and 8b were tested for cytotoxicity in-vitro against three human cancer cell lines (A549, LoVo and Panc-1) and in-vivo zebrafish model, resulting in a good efficacy/safety profile, comparable or superior to the reference drug memantine. Overall, these results encourage further preclinical investigations of 6b and 8b on in-vivo models of neurodegenerative diseases.

Discovery, semisynthesis and neurite outgrowth-promoting activity of novel merrillianone/cycloparviforalone based esters as neurotrophic agents

Natural products (NPs) are very important sources for the development of new drugs. Merrillianone and cycloparvifloralone, isolated from the roots, stems, and fruits of Illicium henryi Diels, are two natural sesquiterpene compounds. In continuation of our effort to discovery more effective neurotrophic compounds from NPs, a series of novel merrillianone/cycloparviforalone based esters 2a-i, 3a-g and 3i-q were prepared and their structures were characterized by ¹H NMR, ¹³C NMR and IR spectral analyses. Furthermore, the spatial structure of compound 2h was unambiguously confirmed by X-ray crystallography. The neurite outgrowth-promoting activity results indicated that most of the target derivatives exhibited more potent neurite outgrowth-promoting activity than merrillianone and cycloparviforalone. Among all target derivatives, the neurite outgrowth-promoting activity of compounds 2a, 3a and 3b was about 2-fold stronger than that of their precursors merrillianone and cycloparviforalone, respectively. Besides, compounds 2a and 3a displayed relatively low cytotoxicity to normal GES-1 cells. Moreover, these derivatives had good hydrolytic stability. Finally, some interesting results of the structure-activity relationships (SARs) were also discussed. This work will pave the way for the development of merrillianone/cycloparviforalone derivatives as potential neurotrophic agents.

Gellan-Based Composite System as a Potential Tool for the Treatment of Nervous Tissue Injuries: Cross-Linked Electrospun Nanofibers Embedded in a RC-33-Loaded Freeze-Dried Matrix

Injuries to the nervous system affect more than one billion people worldwide, and dramatically impact on the patient’s quality of life. The present work aimed to design and develop a gellan gum (GG)-based composite system for the local delivery of the neuroprotective sigma-1 receptor agonist, 1-[3-(1,1′-biphen)-4-yl] butylpiperidine (RC-33), as a potential tool for the treatment of tissue nervous injuries. The system, consisting of cross-linked electrospun nanofibers embedded in a RC-33-loaded freeze-dried matrix, was designed to bridge the lesion gap, control drug delivery and enhance axonal regrowth. The gradual matrix degradation should ensure the progressive interaction between the inner fibrous mat and the surrounding cellular environment. Nanofibers, prepared by electrospinning polymeric solutions containing GG, two different grades of poly (ethylene oxide) and poloxamer, were cross-linked with calcium ions. GG-based matrices, loaded with different amounts of RC-33, were prepared by freeze-drying. Dialysis studies and solid-state characterization pointed out the formation of an interaction product between GG and RC-33. RC-33-loaded freeze-dried matrices were characterized by the capability to absorb a high buffer content, forming a gel with marked viscoelastic properties, and by RC-33 controlled release properties. The presence of cross-linked nanofibers increased matrix mechanical resistance.

Small Molecules Selectively Targeting Sigma-1 Receptor for the Treatment of Neurological Diseases

The sigma-1 (σ1) receptor, an enigmatic protein originally classified as an opioid receptor subtype, is now understood to possess unique structural and functional features of its own and play critical roles to widely impact signaling transduction by interacting with receptors, ion channels, lipids, and kinases. The σ1 receptor is implicated in modulating learning, memory, emotion, sensory systems, neuronal development, and cognition and accordingly is now an actively pursued drug target for various neurological and neuropsychiatric disorders. Evaluation of the five selective σ1 receptor drug candidates (pridopidine, ANAVEX2-73, SA4503, S1RA, and T-817MA) that have entered clinical trials has shown that reaching clinical approval remains an evasive and important goal. This review provides up-to-date information on the selective targeting of σ1 receptors, including their history, function, reported crystal structures, and roles in neurological diseases, as well as a useful collation of new chemical entities as σ1 selective orthosteric ligands or allosteric modulators.

Dual-Functioning Scaffolds for the Treatment of Spinal Cord Injury: Alginate Nanofibers Loaded with the Sigma 1 Receptor (S1R) Agonist RC-33 in Chitosan Films

The present work proposed a novel therapeutic platform with both neuroprotective and neuroregenerative potential to be used in the treatment of spinal cord injury (SCI). A dual-functioning scaffold for the delivery of the neuroprotective S1R agonist, RC-33, to be locally implanted at the site of SCI, was developed. RC-33-loaded fibers, containing alginate (ALG) and a mixture of two different grades of poly(ethylene oxide) (PEO), were prepared by electrospinning. After ionotropic cross-linking, fibers were incorporated in chitosan (CS) films to obtain a drug delivery system more flexible, easier to handle, and characterized by a controlled degradation rate. Dialysis equilibrium studies demonstrated that ALG was able to form an interaction product with the cationic RC-33 and to control RC-33 release in the physiological medium. Fibers loaded with RC-33 at the concentration corresponding to 10% of ALG maximum binding capacity were incorporated in films based on CS at two different molecular weights-low (CSL) and medium (CSM)-solubilized in acetic (AA) or glutamic (GA) acid. CSL- based scaffolds were subjected to a degradation test in order to investigate if the different CSL salification could affect the film behavior when in contact with media that mimic SCI environment. CSL AA exhibited a slower biodegradation and a good compatibility towards human neuroblastoma cell line.

Structural optimization and neurotrophic activity evaluation of neurotrophic gentiside derivatives

C14 alkyl benzoate ABG001, derived from naturally occurring gentisides, was reported to exhibit neurotrophic activity which is similar to NGF (Nerve Growth Factor). In this research, ABG001 was modified by the strategy of isosteric replacement and conformational restriction with the purpose of improving the bioactivity. The cellular neurotrophic activity of those ABG001 derivatives were evaluated, among which 3-hydroxyquinolin-2-(1H)-one A3 and 4-decylphenol ester B7 displayed much better neurotrophic activity compared with ABG001, which highlights the potential of those novel scaffolds for future neurotrophic agent development.

Docking, Interaction Fingerprint, and Three-Dimensional Quantitative Structure-Activity Relationship (3D-QSAR) of Sigma1 Receptor Ligands, Analogs of the Neuroprotective Agent RC-33

The human Sigma1 receptor (S1R), which has been identified as a target with an important role in neuropsychological disorders, was first crystallized 3 years ago. Since S1R structure has no relation with another previous crystallized structures, the presence of the new crystal is an important hallmark for the design of agonists and antagonists against this important target. Some years ago, our group identified RC-33, a potent and selective S1R agonist, endowed with neuroprotective properties. In this work, drawing on new structural information, we studied the interactions of RC-33 and its analogs with the S1R binding site by using computational methods such as docking, interaction fingerprints, and receptor-guided alignment three dimensional quantitative structure–activity relationship (3D-QSAR). We found that RC-33 and its analogs adopted similar orientations within S1R binding site, with high similitude with orientations of the crystallized ligands; such information was used for identifying the residues involved in chemical interactions with ligands. Furthermore, the structure-activity relationship of the studied ligands was adequately described considering classical QSAR tests. All relevant aspects of the interactions between the studied compounds and S1R were covered here, through descriptions of orientations, binding interactions, and features that influence differential affinities. In this sense, the present results could be useful in the future design of novel S1R modulators.

Novel Compounds Targeting the RNA-Binding Protein HuR. Structure-Based Design, Synthesis, and Interaction Studies

The key role of RNA-binding proteins (RBPs) in regulating post-transcriptional processes and their involvement in several pathologies (i.e., cancer and neurodegeneration) have highlighted their potential as therapeutic targets. In this scenario, Embryonic Lethal Abnormal Vision (ELAV) or Hu proteins and their complexes with target mRNAs have been gaining growing attention. Compounds able to modulate the complex stability could constitute an innovative pharmacological strategy for the treatment of numerous diseases. Nevertheless, medicinal-chemistry efforts aimed at developing such compounds are still at an early stage. As part of our ongoing research in this field, we hereby present the rational design and synthesis of structurally novel HuR ligands, potentially acting as HuR-RNA interferers. The following assessment of the structural features of their interaction with HuR, combining saturation-transfer difference NMR and in silico studies, provides a guide for further research on the development of new effective interfering compounds of the HuR-RNA complex.

Structural Insights into σ₁ Receptor Interactions with Opioid Ligands by Molecular Dynamics Simulations

Despite considerable advances over the past years in understanding the mechanisms of action and the role of the σ₁ receptor, several questions regarding this receptor remain unanswered. This receptor has been identified as a useful target for the treatment of a diverse range of diseases, from various central nervous system disorders to cancer. The recently solved issue of the crystal structure of the σ₁ receptor has made elucidating the structure-activity relationship feasible. The interaction of seven representative opioid ligands with the crystal structure of the σ₁ receptor (PDB ID: 5HK1) was simulated for the first time using molecular dynamics (MD). Analysis of the MD trajectories has provided the receptor-ligand interaction fingerprints, combining information on the crucial receptor residues and frequency of the residue-ligand contacts. The contact frequencies and the contact maps suggest that for all studied ligands, the hydrophilic (hydrogen bonding) interactions with Glu172 are an important factor for the ligands' affinities toward the σ₁ receptor. However, the hydrophobic interactions with Tyr120, Val162, Leu105, and Ile124 also significantly contribute to the ligand-receptor interplay and, in particular, differentiate the action of the agonistic morphine from the antagonistic haloperidol.

Discovery of N-cyclobutylaminoethoxyisoxazole derivatives as novel sigma-1 receptor ligands with neurite outgrowth efficacy in cells

Herein we reported a series of 14 novel derivatives based on the N-cyclobutylaminoethoxyisoxazole scaffold. In vitro binding studies of these compounds demonstrated their low nanomolar to subnanomolar potencies as σ1 receptor ligands, with moderate to excellent selectivity over the σ2 receptor as represented by compounds 17–30. The majority of the derivatives scored high (>4.7) in the CNS MPO appraisal system, indicating their high likelihood in penetrating the blood–brain barrier. A number of these compounds exhibited significant neurite outgrowth efficacy in N1E-115 neuronal cells and displayed excellent selectivity for σ1 receptors over the selected endogenous neurotransmitter transporters, such as DAT, NET and SERT. Among the mini-series, compound 28 (K_i σ1 = 0.2 nM, K_i σ2 = 198 nM, CNS MPO score = 5.4) emerged as a promising selective σ1 receptor ligand that warrants its further evaluation as a potential therapeutic for neurodegenerative diseases.

Herein we reported a series of 14 novel derivatives based on the N-cyclobutylaminoethoxyisoxazole scaffold.

Thiazole-Based σ1 Receptor Ligands: Diversity by Late-Stage C-H Arylation of Thiazoles, Structure-Affinity and Selectivity Relationships, and Molecular Interactions

Spirocyclic thiophene derivatives represent promising σ1 ligands with high σ1 affinity and selectivity over the σ2 subtype. To increase ligand efficiency, the thiophene ring was replaced bioisosterically by a thiazole ring, and the pyran ring was opened. Late-stage diversification by regioselective C-H arylation of thiazoles 9 a-c resulted in a set of 53 compounds with high diversity. This set of compounds was analyzed with respect to σ1 affinity, σ1 /σ2 selectivity, lipophilicity (logD7.4 ), lipophilicity-corrected ligand efficiency (LELP), and molecular target interactions. The most promising candidates were pyridyl-substituted thiazole derivatives 33 c (2-(1-benzyl-4-ethoxypiperidin-4-yl)-5-(pyridin-3-yl)thiazole) and 34 c (2-(1-benzyl-4-ethoxypiperidin-4-yl)-5-(pyridin-4-yl)thiazole), possessing low-nanomolar σ1 affinity (Ki =1.3 and 1.9 nm), high σ1 /σ2 selectivity (>1500-fold), low lipophilicity (logD7.4 =1.8) and very good ligand efficiency (LELP=5.5), indicating promising pharmacodynamics and pharmacokinetics. Molecular simulation studies, including docking and deconvolution of the free binding energy into its major components, led to decreased hydrophobic stabilization of pyridyl derivatives 33 c and 34 c, which was compensated by lower desolvation energy.

Design, synthesis and evaluation of new ligustrazine derivatives as potential plasma-stable neuroprotective agents

A series of ligustrazine-phenolic acid esters which exhibited promising neuroprotective activities have previously been reported. Nevertheless, we found that these ester compounds (like T-VA) were not stable in plasma by further in vivo studies. To investigate plasma-stable neuroprotective agents, a series of new ligustrazine derivatives were synthesized by conjoining ligustrazine and phenols with ester, ether and amide bonds. Most of the compounds exhibited higher protective effects against CoCl₂-induced neurotoxicity in differentiated PC12 cells than ligustrazine. Structure-activity relationships were also briefly discussed. We found that compound 2c (2-((2-methoxy-4-(((3,5,6-trimethylpyrazin-2-yl)methoxy) methyl)phenoxy)methyl)-3,5,6-trimethylpyrazine) displayed the highest protective effect on the PC12 cells damaged by CoCl₂ (EC₅₀ = 1.07 μM). Preliminary stability investigation in rat plasma was verified in vitro and better plasma stability was observed with 2c in comparison to T-VA.

The role of chirality in a set of key intermediates of pharmaceutical interest, 3-aryl-substituted-γ-butyrolactones, evidenced by chiral HPLC separation and by chiroptical spectroscopies

The enantiomers of four chiral 3-aryl-substituted-γ-butyrolactones, key intermediates for the preparation of compounds of pharmaceutical interest, were successfully isolated by enantioselective chromatography, employing the Chiralpak AD-H chiral stationary phase. For all compounds the same elution order was observed, as monitored by a full set of chiroptical methods that we employed, namely ORD (optical rotatory dispersion), ECD (electronic circular dichroism, or CD in the UV range), and VCD (vibrational circular dichroism, or CD in the IR range). By density functional theory (DFT) calculations we were able to determine that the first eluted enantiomer has (S) absolute configuration in all four cases. We were able to justify the elution order by molecular docking calculations for all four enantiomeric pairs and suitable modeling of the stationary and mobile phases of the employed columns. The optimal performance of the chiroptical spectroscopies and of the DFT calculations allows us to formulate a lactone chirality rule out of the CO stretching region of the VCD spectra.

Role of σ1 Receptors in Learning and Memory and Alzheimer's Disease-Type Dementia

The present chapter will review the role of σ1 receptor in learning and memory and neuroprotection , against Alzheimer's type dementia. σ1 Receptor agonists have been tested in a variety of pharmacological and pathological models of learning impairments in rodents these last past 20 years. Their anti-amnesic effects have been explained by the wide-range modulatory role of σ1 receptors on Ca2+ mobilizations, neurotransmitter responses, and particularly glutamate and acetylcholine systems, and neurotrophic factors. Recent observations from genetic and pharmacological studies have shown that σ1 receptor can also be targeted in neurodegenerative diseases, and particularly Alzheimer's disease . Several compounds, acting partly through the σ1 receptor, have showed effective neuroprotection in transgenic mouse models of Alzheimer's disease . We will review the data and discuss the possible mechanisms of action, particularly focusing on oxidative stress and mitochondrial integrity, trophic factors and a novel hypothesis suggesting a functional interaction between the σ1 receptor and α7 nicotinic acetylcholine receptor. Finally, we will discuss the pharmacological peculiarities of non-selective σ1 receptor ligands, now developed as neuroprotectants in Alzheimer's disease , and positive modulators, recently described and that showed efficacy against learning and memory deficits.

3D Homology Model of Sigma1 Receptor

This chapter presents the three-dimensional (3D) model of the Sigma1 receptor protein as obtained from homology modeling techniques. We show the applicability of this structure to docking-based virtual screening and discuss combined in silico/in vitro mutagenesis studies performed to validate the structural features of the Sigma1 receptor model and to qualify/quantify the prominent role of specific amino acid residues in ligand binding. The validation of the virtual 3D Sigma1 receptor model and its reliable applicability to docking-based virtual screening is of significance for rational ligand design, even in light of the recently reported crystal structure for the Sigma1 receptor.

Gaining in pan-affinity towards sigma 1 and sigma 2 receptors. SAR studies on arylalkylamines

Sigma Receptor (SR) modulators are involved in different signal transduction pathways, representing important pharmacological/therapeutic tools in several pathological conditions, such as neurodegenerative diseases and cancers. To this purpose, numerous compounds have been developed in order to target selectively one of the two subtypes (S1R and S2R) as chemotherapeutic agent. However, experiments have also shown that ligands which are able to bind both SR subtypes can be useful for the diagnosis and/or the treatment of cancers. Therefore, the discovery of compounds with good affinity towards both S1R and S2R ('pan-modulators') is also of great interest and still represents a challenge up to now. For this reason, we synthesized novel arylalkylamines with the aim to obtain compounds with S1R and S2R affinity in the nM range and, by modeling quantitative structure-activity relationships (QSARs), we identified the essential structural features to obtain promising pan-compounds.

Novel Enantiopure Sigma Receptor Modulators: Quick (Semi-)Preparative Chiral Resolution via HPLC and Absolute Configuration Assignment

The identification of novel pan-sigma receptor (SR) modulators, potentially useful in cancer treatment, represents a new goal of our research. Here, we report on the preparation of novel chiral compounds characterized by a 3-C alkyl chain bridging an aromatic portion to a 4-benzyl-piperidine moiety. All of the studied compounds have been prepared both in racemic and enantiomerically-pure form, with the final aim to address the role of chirality in the SR interaction. To isolate and characterize enantiomeric compounds, high-performance liquid chromatography (HPLC) procedures were set up. A systematic analytical screening, involving several combinations of chiral stationary and mobile phases, allowed us to optimize the analytical resolution and to set up the (semi-)preparative chromatographic conditions. Applying the optimized procedure, the enantiomeric resolution of the studied compounds was successfully achieved, obtaining all of the compounds with an enantiomeric excess higher than 95%. Lastly, the absolute configuration has been empirically assigned to enantiopure compounds, combining the electronic circular dichroism (ECD) technique to the elution order study.

Synthesis and biological evaluation of new aryl-alkyl(alkenyl)-4-benzylpiperidines, novel Sigma Receptor (SR) modulators, as potential anticancer-agents

In the early 2000s, the Sigma Receptor (SR) family was identified as potential "druggable" target in cancer treatment. Indeed, high density of SRs was found in breast, lung, and prostate cancer cells, supporting the idea that SRs could play a role in tumor growth and progression. Moreover, a link between the degree of SR expression and tumor aggressiveness has been postulated, justified by the presence of SRs in high metastatic-potential cancer cells. As a consequence, considerable efforts have been devoted to the development of small molecules endowed with good affinity towards the two SR subtypes (S1R and S2R) with potential anticancer activity. Herein, we report the synthesis and biological profile of aryl-alkyl(alkenyl)-4-benzylpiperidine derivatives - as novel potential anticancer drugs targeting SR. Among them, 3 (RC-106) exhibited a preclinical profile of antitumor efficacy on a panel of cell lines representative of different cancer types (i.e. Paca3, MDA-MB 231) expressing both SRs, and emerged as a hit compound of a new class of SR modulators potentially useful for the treatment of cancer disease.

New neurogenic lipoic-based hybrids as innovative Alzheimer's drugs with σ-1 agonism and β-secretase inhibition

BACKGROUND

Neurogenic agents emerge as innovative drugs for the treatment of Alzheimer's disease (AD), whose pathological complexity suggests strengthening research in the multi-target directed ligands strategy.

RESULTS

By combining the lipoic acid structure with N-benzylpiperidine or N,N-dibenzyl(N-methyl)amine fragments, new multi-target directed ligands were obtained that act at three relevant targets in AD: σ-1 receptor (σ1R), β-secretase-1 (BACE1) and acetylcholinesterase (AChE). Moreover, they show potent neurogenic properties, good antioxidant capacity and favorable CNS permeability. Molecular modeling studies on AChE, σ1R and BACE1 highlight relevant drug-protein interactions that may contribute to the development of new disease-modifying drugs.

CONCLUSION

New lipoic-based σ1 agonists endowed with neurogenic, antioxidant, cholinergic and amyloid β-peptide-reducing properties have been discovered for the potential treatment of AD.

Development of easy-to-use reverse-phase liquid chromatographic methods for determining PRE-084, RC-33 and RC-34 in biological matrices. The first step for in vivo analysis of sigma1 receptor agonists

Over the years there has been a growing interest in the therapeutic potential for central nervous system pathologies of sigma receptor modulators. The widely studied PRE-084 and our compounds RC-33 and RC-34 are very potent and selective sigma 1 receptor agonists that could represent promising drug candidates for Amyotrophic Lateral Sclerosis (ALS). Herein, we develop and validate robust and easy-to-use reverse-phase chromatographic methods suitable for detecting and quantifying PRE-084, RC-33 and RC-34 in mouse blood, brain and spinal cord. An HPLC/UV/ESI-MS system was employed for analyzing PRE-084 and an HPLC/UV-PDA system for determining RC-33 and RC-34. Chromatographic separations were achieved on Waters Symmetry RP18 column (150 × 3.9 mm, 5 µm), eluting with water and acetonitrile (both containing 0.1% formic acid) in gradient conditions. The recovery of PRE-084, RC-33 and RC-34 was >95% in all the considered matrices. Their limits of quantitation and detection were also determined. Validation proved the methods be suitable for separating tested compounds from endogenous interferences, being characterized by good sensitivity, linearity, precision and accuracy. A preliminary central nervous system distribution study showed a high distribution of RC-33 in brain and spinal cord, with concentration values well above the determined limit of quantitation. The proposed methods will be used in future preclinical investigations.

Toward the identification of neuroprotective agents: g-scale synthesis, pharmacokinetic evaluation and CNS distribution of (R)-RC-33, a promising SIGMA1 receptor agonist

AIM

Nowadays, there is a great interest in the therapeutic potential of sigma1 receptor ligands for treating different CNS pathologies. Our previous investigations led to identify (R)-RC-33 as a potent and selective S1R agonist.

RESULTS

Herein, we report the gram-scale synthesis, pharmacokinetic profile and CNS distribution of (R)-RC-33 in the mouse to determine the most suitable dosage schedule for in vivo administration. For comparative purposes, the same experiments were also performed with PRE-084, the most widely used S1R agonist commonly in pharmacological experiments.

DISCUSSION

(R)-RC-33 shows a similar pharmacokinetic profile and a better CNS distribution when compared with PRE-084.

CONCLUSION

(R)-RC-33 may be a promising candidate for in vivo studies in animal models of neurodegenerative diseases.

Improving selectivity preserving affinity: new piperidine-4-carboxamide derivatives as effective sigma-1-ligands

We report the design, synthesis and binding evaluation against σ1 and σ2 receptors of a series of new piperidine-4-carboxamide derivatives variously substituted on the amide nitrogen atom. Specifically, we assessed the effects exerted on σ receptor affinity by substituting the N-benzylcarboxamide group present on a series of compounds previously synthesized in our laboratory with different cyclic or linear moieties. The synthesized compounds 2a-o were tested to estimate their affinity and selectivity toward σ1 and σ2 receptors. Very high σ1 affinity (Ki = 3.7 nM) and Kiσ2/Kiσ1 selectivity ratio (351) were found for the tetrahydroquinoline derivative 2k, featuring a 4-chlorobenzyl moiety linked to the piperidine nitrogen atom.

Beyond the affinity for protein kinase C: exploring 2-phenyl-3-hydroxypropyl pivalate analogues as C1 domain-targeting ligands

Over the past fifteen years, we reported the design and synthesis of different series of compounds targeting the C1 domain of protein kinase C (PKC) that were based on various templates.

A step forward in the sigma enigma: a role for chirality in the sigma1 receptor–ligand interaction?

To investigate the role of chirality in the ligand–σ₁ receptor interaction, a series of enantiomeric arylalkylaminoalcohols and arylpyrrolidinols was evaluated by means of both in silico and in vitro studies.

Selective sigma-1 receptor antagonists for the treatment of pain

The sigma-1 receptor (σ1R) is located in areas of the CNS key for pain control and belongs to a unique target class with chaperoning functions over different molecular targets involved in transmission and amplification of nociceptive messages. Preclinical evidence supports a role for σ1R antagonists in the treatment of pain states where hypersensitivity develops as hyperalgesia and allodynia, two common symptoms encountered in neuropathic and other chronic pain conditions. Additionally, σ1R antagonists increase opioid analgesia without increasing opioid-related unwanted effects, which point to their potential use as opioid adjuvant therapy. This review summarizes the structure and function of the σ1R as well as the medicinal chemistry and pharmacological studies directed to the identification of σ1R antagonists for the treatment of pain.

Synthesis and receptor binding studies of some new arylcarboxamide derivatives as sigma-1 ligands

We describe here the synthesis and the binding interaction with σ1 and σ2 receptors of a series of new arylcarboxamide derivatives variously substituted on the aromatic portions. Maintaining a partial scaffold of a series of compounds previously synthesized by us, we evaluate the effect of the substitution on σ binding. The synthesized compounds have been tested to estimate their affinity and selectivity toward σ1 and σ2 receptors. Two out of 16 derivatives showed an interesting σ1 affinity (21.2 and 13.6 nM-compounds 2m and 2p) and a good selectivity (Ki(σ2)/Ki(σ1) >140 and >40, respectively).