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

Recent Advances in the Development of Sigma Receptor (Radio)Ligands and Their Application in Tumors

Cancer ranks among the top triumvirate leading causes of human deaths worldwide. The pathological mechanisms are notably intricate, demonstrating proliferative and metastatic capabilities, which complicate therapeutic interventions. The sigma-1 receptor (σ1R) plays a crucial role in tumor survival and migration, while the sigma-2 receptor (σ2R) is intimately associated with tumor proliferation. This review encapsulated the investigation concerning σ1R and σ2R in neoplasms and rigorously summarized the ligands and radio-ligands development and their tumor applications, such as antitumor cell proliferation and PET/SPECT imaging in tumors. A comprehensive classification discussion was undertaken regarding the chemical structures and emphasized the possibility of dual/multitargeted ligands. Ultimately, we discussed the effects of chiral structures and the pharmacological characteristics of ligands on affinity and pharmacokinetic features in vivo, particularly concerning radiopharmaceuticals. This review functions as a beneficial resource, fostering ligand deployment and stimulating the generation of innovative ideas for developing innovative radiopharmaceuticals.

Novel sigma 1-antagonists with cis-(+)-normetazocine scaffold: synthesis, molecular modeling, and antinociceptive effect

Inflammatory pain represents one of the unmet clinical needs for patients, as conventional therapies cause several side effects. Recently, new targets involved in inflammatory pain modulation have been identified, including the sigma-1 receptor (σ1R). Selective σ1R antagonists have demonstrated analgesic efficacy in acute and chronic inflammatory pain models. Considering these findings, a series of novel N-normetazocine derivatives has been designed and synthesized to investigate the pivotal role of N-normetazocine stereochemistry in their pharmacological fingerprint. The affinity profile of new ligands versus sigma receptors and opioid receptors was evaluated in vitro, and compound 7 showed a relevant σ1R affinity, with K iσ1 = 27.5 ± 8.1 nM, and selectivity over sigma-2 receptor (σ2R) and opioid receptors. Furthermore, in vivo, compound 7 significantly reduced inflammatory pain in the second phase of the formalin test. Molecular modeling studies were also performed to analyze the binding mode and the key interactions between the new ligands and σ1R.

Sigma receptor and aquaporin modulators: chiral resolution, configurational assignment, and preliminary biological profile of RC752 enantiomers

The key role of chiral small molecules in drug discovery programs has been deeply investigated throughout last decades. In this context, our previous studies highlighted the influence of the absolute configuration of different stereocenters on the pharmacokinetic, pharmacodynamic and functional properties of promising Sigma receptor (SR) modulators. Thus, starting from the racemic SR ligand RC752, we report herein the isolation of the enantiomers via enantioselective separation with both HPLC and SFC. After optimization of the eco-sustainable chiral SFC method, both enantiomers were obtained in sufficient amount (tens of mg) and purity (ee up to 95%) to allow their characterization and initial biological investigation. Both enantiomers a) displayed a high affinity for the S1R subtype (Ki = 15.0 ± 1.7 and 6.0 ± 1.2 nM for the (S)- and (R)-enantiomer, respectively), but only negligible affinity toward the S2R (> 350 nM), and b) were rapidly metabolized when incubated with mouse and human hepatic microsomes. Furthermore, the activity on AQP-mediated water permeability indicated a different functional profile for the enantiomers in terms of modulatory effect on the peroxiporins gating.

Discovery of first novel sigma/HDACi dual-ligands with a potent in vitro antiproliferative activity

Designing and discovering compounds for dual-target inhibitors is challenging to synthesize new, safer, and more efficient drugs than single-target drugs, especially to treat multifactorial diseases such as cancer. The simultaneous regulation of multiple targets might represent an alternative synthetic approach to optimize patient compliance and tolerance, minimizing the risk of target-based drug resistance due to the modulation of a few targets. To this end, we conceived for the first time the design and synthesis of dual-ligands σR/HDACi to evaluate possible employment as innovative candidates to address this complex disease. Among all synthesized compounds screened for several tumoral cell lines, compound 6 (Kiσ1R = 38 ± 3.7; Kiσ2R = 2917 ± 769 and HDACs IC50 = 0.59 µM) is the most promising candidate as an antiproliferative agent with an IC50 of 0.9 µM on the HCT116 cell line and no significant toxicity to normal cells. Studies of molecular docking, which confirmed the affinity over σ1R and a pan-HDACs inhibitory behavior, support a possible balanced affinity and activity between both targets.

Discovery of RC-752, a Novel Sigma-1 Receptor Antagonist with Antinociceptive Activity: A Promising Tool for Fighting Neuropathic Pain

Neuropathic pain (NP) is a chronic condition resulting from damaged pain-signaling pathways. It is a debilitating disorder that affects up to 10% of the world's population. Although opioid analgesics are effective in reducing pain, they present severe risks; so, there is a pressing need for non-opioid pain-relieving drugs. One potential alternative is represented by sigma-1 receptor (S1R) antagonists due to their promising analgesic effects. Here, we report the synthesis and biological evaluation of a series of S1R antagonists based on a 2-aryl-4-aminobutanol scaffold. After assessing affinity toward the S1R and selectivity over the sigma-2 receptor (S2R), we evaluated the agonist/antagonist profile of the compounds by investigating their effects on nerve growth factor-induced neurite outgrowth and aquaporin-mediated water permeability in the presence and absence of oxidative stress. (R/S)-RC-752 emerged as the most interesting compound for S1R affinity (K_i S1R = 6.2 ± 0.9) and functional antagonist activity. Furthermore, it showed no cytotoxic effect in two normal human cell lines or in an in vivo zebrafish model and was stable after incubation in mouse plasma. (R/S)-RC-752 was then evaluated in two animal models of NP: the formalin test and the spinal nerve ligation model. The results clearly demonstrated that compound (R/S)-RC-752 effectively alleviated pain in both animal models, thus providing the proof of concept of its efficacy as an antinociceptive agent.

Structural Insights into the Ligand–LsrK Kinase Binding Mode: A Step Forward in the Discovery of Novel Antimicrobial Agents

LsrK is a bacterial kinase that triggers the quorum sensing, and it represents a druggable target for the identification of new agents for fighting antimicrobial resistance. Herein, we exploited tryptophan fluorescence spectroscopy (TFS) as a suitable technique for the identification of potential LsrK ligands from an in-house library of chemicals comprising synthetic compounds as well as secondary metabolites. Three secondary metabolites (Hib-ester, Hib-carbaldehyde and (R)-ASME) showed effective binding to LsrK, with KD values in the sub-micromolar range. The conformational changes were confirmed via circular dichroism and molecular docking results further validated the findings and displayed the specific mode of interaction. The activity of the identified compounds on the biofilm formation by some Staphylococcus spp. was investigated. Hib-carbaldehyde and (R)-ASME were able to reduce the production of biofilm, with (R)-ASME resulting in the most effective compound with an EC50 of 14 mg/well. The successful application of TFS highlights its usefulness in searching for promising LsrK inhibitor candidates with inhibitor efficacy against biofilm formation.

From Nature to Synthetic Compounds: Novel 1(N),2,3 Trisubstituted-5-oxopyrrolidines Targeting Multiple Myeloma Cells

The insurgence of drug resistance in treating Multiple Myeloma (MM) still represents a major hamper in finding effective treatments, although over the past decades new classes of drugs, such as proteasome inhibitors and immunomodulatory drugs, have been discovered. Recently, our research team, within a Nature-Aided Drug Discovery project, isolated from Hibiscus Sabdariffa L. calyces the secondary metabolite called Hib-ester which possesses antiproliferative properties against human multiple myeloma RPMI 8226 cells, reduces migration and cell invasion and inhibits proteasome without neurotoxic effects. In the present study, we explored the chemical spaces of the hit compound Hib-ester. We explored the structure-activity relationships (SAR), and we optimized the scaffold through sequentially modifying Hib-ester subunits. Compound screening was performed based on cytotoxicity against the RPMI 8226 cells to assess the potential efficacy toward human MM. The ability of the most effective molecules to inhibit the proteasome was evaluated and the binding mode of the most promising compounds in the proteasome chymotrypsin binding pocket was deciphered through molecular modeling simulations. Compounds 13 and 14 are more potent than Hib-ester, demonstrating that our strategy was suitable for the identification of a novel chemotype for developing possible drug candidates and hopefully widening the drug armamentarium against MM.

Structural Optimization and Improving Antitumor Potential of Moreollic Acid from Gamboge

Moreollic acid, a caged-tetraprenylated xanthone from Gamboge, has been indicated as a potent antitumor molecule. In the present study, a series of moreollic acid derivatives with novel structures were designed and synthesized, and their antitumor activities were determined in multifarious cell lines. The preliminary screening results showed that all synthesized compounds selectively inhibited human colon cancer cell proliferation. TH12-10, with an IC50 of 0.83, 1.10, and 0.79 μM against HCT116, DLD1, and SW620, respectively, was selected for further antitumor mechanism studies. Results revealed that TH12-10 effectively inhibited cell proliferation by blocking cell-cycle progression from G1 to S. Besides, the apparent structure-activity relationships of target compounds were discussed. To summarize, a series of moreollic acid derivatives were discovered to possess satisfactory antitumor potentials. Among them, TH12-10 displays the highest antitumor activities against human colon cancer cells, in which the IC50 values in DLD1 and SW620 are lower than that of 5-fluorouracil.

Sigma-1 Receptor Agonists Acting on Aquaporin-Mediated H2O2 Permeability: New Tools for Counteracting Oxidative Stress

Sigma1 Receptor (S1R) is involved in oxidative stress, since its activation is triggered by oxidative or endoplasmic reticulum stress. Since specific aquaporins (AQP), called peroxiporins, play a relevant role in controlling H2O2 permeability and ensure reactive oxygen species wasted during oxidative stress, we studied the effect of S1R modulators on AQP-dependent water and hydrogen peroxide permeability in the presence and in the absence of oxidative stress. Applying stopped-flow light scattering and fluorescent probe methods, water and hydrogen peroxide permeability in HeLa cells have been studied. Results evidenced that S1R agonists can restore water permeability in heat-stressed cells and the co-administration with a S1R antagonist totally counteracted the ability to restore the water permeability. Moreover, compounds were able to counteract the oxidative stress of HeLa cells specifically knocked down for S1R. Taken together these results support the hypothesis that the antioxidant mechanism is mediated by both S1R and AQP-mediated H2O2 permeability. The finding that small molecules can act on both S1R and AQP-mediated H2O2 permeability opens a new direction toward the identification of innovative drugs able to regulate cell survival during oxidative stress in pathologic conditions, such as cancer and degenerative diseases.

σ2 Receptor and Its Role in Cancer with Focus on a MultiTarget Directed Ligand (MTDL) Approach

Sigma-2 (σ2) is an endoplasmic receptor identified as the Endoplasmic Reticulum (ER) transmembrane protein TMEM97. Despite its controversial identity, which was only recently solved, this protein has gained scientific interest because of its role in the proliferative status of cells; many tumor cells from different organs overexpress the σ2 receptor, and many σ2 ligands display cytotoxic actions in (resistant) cancer cells. These properties have shed light on the σ2 receptor as a potential druggable target to be bound/activated for the diagnosis or therapy of tumors. Additionally, diverse groups have shown how the σ2 receptor can be exploited for the targeted delivery of the anticancer drugs to tumors. As the cancer disease is a multifactorial pathology with multiple cell populations, a polypharmacological approach is very often needed. Instead of the simultaneous administration of different classes of drugs, the use of one molecule that interacts with diverse pharmacological targets, namely MultiTarget Directed Ligand (MTDL), is a promising and currently pursued strategy, that may overcome the pharmacokinetic problems associated with the administration of multiple molecules. This review aims to point out the progress regarding the σ2 ligands in the oncology field, with a focus on MTDLs directed towards σ2 receptors as promising weapons against (resistant) cancer diseases.

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.

Pan-Sigma Receptor Modulator RC-106 Induces Terminal Unfolded Protein Response In In Vitro Pancreatic Cancer Model

Pancreatic cancer (PC) remains one of the most lethal cancers worldwide. Sigma receptors (SRs) have been proposed as cancer therapeutic targets. Their main localization suggests they play a potential role in ER stress and in the triggering of the unfolded protein response (UPR). Here, we investigated the mechanisms of action of RC-106, a novel pan-SR modulator, to characterize therapeutically exploitable role of SRs in tumors. Two PC cell lines were used in all the experiments. Terminal UPR activation was evaluated by quantifying BiP, ATF4 and CHOP by Real-Time qRT-PCR, Western Blot, immunofluorescence and confocal microscopy. Cell death was studied by flow cytometry. Post-transcriptional gene silencing was performed to study the interactions between SRs and UPR key proteins. RC-106 activated ER stress sensors in a dose- and time-dependent manner. It also induced ROS production accordingly with ATF4 upregulation at the same time reducing cell viability of both cell lines tested. Moreover, RC-106 exerted its effect through the induction of the terminal UPR, as shown by the activation of some of the main transducers of this pathway. Post-transcriptional silencing studies confirmed the connection between SRs and these key proteins. Overall, our data highlighted a key role of SRs in the activation of the terminal UPR pathway, thus indicating pan-SR ligands as candidates for targeting the UPR in pancreatic cancer.

Synthesis and Pharmacological Evaluation of σ2 Receptor Ligands Based on a 3-Alkoxyisoxazole Scaffold: Potential Antitumor Effects against Osteosarcoma

Since its initial discovery as the basis for nicotinic acetylcholine receptor ligands, the 3-alkoxyisoxazole scaffold has been shown to be a versatile platform for the development of potent σ1 and σ2 receptor ligands. Herein we report a further SAR exploration of the 3-alkoxyisoxazole scaffold with the aim of obtaining potent σ2 receptor ligands. Various substitutions on the benzene ring and at the basic amino regions resulted in a total of 21 compounds that were tested for their binding affinities for the σ2 receptor. In particular, compound 51 [(2S)-1-(4-ammoniobutyl)-2-(((5-((3,4-dichlorophenoxy)methyl)isoxazol-3-yl)oxy)methyl)pyrrolidin-1-ium chloride] was identified as one of the most potent σ2 ligands within the series, with a K_i value of 7.9 nM. It demonstrated potent antiproliferative effects on both osteosarcoma cell lines 143B and MOS-J (IC₅₀ values of 0.89 and 0.71 μM, respectively), relative to siramesine (IC₅₀ values of 1.81 and 2.01 μM). Moreover, compound 51 inhibited clonal formation of osteosarcoma 143B cells at 1 μM, corresponding to half the dose required of siramesine for similar effects. The general cytotoxicity profile of compound 51 was assessed in a number of normal cell lines, including HaCaT, HAF, and LO2 cells. Furthermore, FACS analysis showed that compound 51 likely inhibits osteosarcoma cell growth by disruption of the cell cycle and promotion of apoptosis.

Exploring the RC-106 Chemical Space: Design and Synthesis of Novel (E)-1-(3-Arylbut-2-en-1-yl)-4-(Substituted) Piperazine Derivatives as Potential Anticancer Agents

Despite the fact that significant advances in treatment of common cancers have been achieved over the years, orphan tumors still represent an important unmet medical need. Due to their complex multifactorial origin and limited number of cases, such pathologies often have very limited treatment options and poor prognosis. In the search for new anticancer agents, our group recently identified RC-106, a Sigma receptor modulator endowed with proteasome inhibition activity. This compound showed antiproliferative activity toward different cancer cell lines, among them glioblastoma (GB) and multiple myeloma (MM), two currently unmet medical conditions. In this work, we directed our efforts toward the exploration of chemical space around RC-106 to identify new active compounds potentially useful in cancer treatment. Thanks to a combinatorial approach, we prepared 41 derivatives of the compound and evaluated their cytotoxic potential against MM and GB. Three novel potential anticancer agents have been identified.

Sigma-1 receptor antagonists: promising players in fighting neuropathic pain

Sigma-1 receptors (S1Rs) are strongly correlated to neuropathic pain (NP), since their inactivation may decrease allodynia or dysesthesia, promoting analgesic effects. In the recent patent landscape, S1R antagonists endowed with nanomolar S1Rs affinity emerged as potent antinociceptive agents. So far, three patented compounds have been proposed for counteracting NP. Particularly PV-752 and AV1066, disclosed by the University of Pavia (Italy) and Anavex, respectively, showed good analgesic activity in preclinical studies. Moreover, E-52862 developed by Esteve (Spain) has been proved to be effective, both in preclinical and Phase II clinical trials, against several symptoms of NP. These patents ascertain S1R antagonists as potential drugs, alone or in combination with other analgesic drugs, for managing NP in humans.

Piperidine propionamide as a scaffold for potent sigma-1 receptor antagonists and mu opioid receptor agonists for treating neuropathic pain

We designed and synthesized a novel series of piperidine propionamide derivatives as potent sigma-1 (σ1) receptor antagonists and mu (μ) opioid receptor agonists, and measured their affinity for σ1 and μ receptors in vitro through binding assays. The basic scaffold of the new compounds contained a 4-substituted piperidine ring and N-aryl propionamide. Compound 44, N-(2-(4-(4-fluorobenzyl) piperidin-1-yl) ethyl)-N-(4-methoxy-phenyl) propionamide, showed the highest affinity for σ1 receptor (Ki σ1 = 1.86 nM) and μ receptor (Ki μ = 2.1 nM). It exhibited potent analgesic activity in the formalin test (ED50 = 15.1 ± 1.67 mg/kg) and had equivalent analgesic effects to S1RA (σ1 antagonist) in a CCI model. Therefore, Compound 44, which has mixed σ1/μ receptor profiles, may be a potential candidate for treating neuropathic pain.

Design and Synthesis of Benzimidazole-Chalcone Derivatives as Potential Anticancer Agents

Numerous reports have shown that conjugated benzimidazole derivatives possess various kinds of biological activities, including anticancer properties. In this report, we designed and synthesized 24 new molecules comprising a benzimidazole ring, arene, and alkyl chain-bearing cyclic moieties. The results showed that the N-substituted benzimidazole derivatives bearing an alkyl chain and a nitrogen-containing 5- or 6-membered ring enhanced the cytotoxic effects on human breast adenocarcinoma (MCF-7) and human ovarian carcinoma (OVCAR-3) cell lines. Among the 24 synthesized compounds, (2E)-1-(1-(3-morpholinopropyl)-1H-benzimidazol-2 -yl)-3-phenyl-2-propen-1-one) (23a) reduced the proliferation of MCF-7 and OVCAR-3 cell lines demonstrating superior outcomes to those of cisplatin.

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.

Anti-tumor Efficacy Assessment of the Sigma Receptor Pan Modulator RC-106. A Promising Therapeutic Tool for Pancreatic Cancer

Introduction: Pancreatic cancer (PC) is one of the most lethal tumor worldwide, with no prognosis improvement over the past 20-years. The silent progressive nature of this neoplasia hampers the early diagnosis, and the surgical resection of the tumor, thus chemotherapy remains the only available therapeutic option. Sigma receptors (SRs) are a class of receptors proposed as new cancer therapeutic targets due to their over-expression in tumor cells and their involvement in cancer biology. The main localization of these receptors strongly suggests their potential role in ER unfolded protein response (ER-UPR), a condition frequently occurring in several pathological settings, including cancer. Our group has recently identified RC-106, a novel pan-SR modulator with good in vitro antiproliferative activities toward a panel of different cancer cell lines. In the present study, we investigated the in vitro properties and pharmacological profile of RC-106 in PC cell lines with the aim to identify a potential lead candidate for the treatment of this tumor. Methods: Pancreatic cancer cell lines Panc-1, Capan-1, and Capan-2 have been used in all experiments. S1R and TMEM97/S2R expression in PC cell lines was quantified by Real-Time qRT-PCR and Western Blot experiments. MTS assay was used to assess the antiproliferative effect of RC-106. The apoptotic properties of RC-106 was evaluated by TUNEL and caspase activation assays. GRP78/BiP, ATF4, and CHOP was quantified to evaluate ER-UPR. Proteasome activity was investigated by a specific fluorescent-based assay. Scratch wound healing assay was used to asses RC-106 effect on cell migration. In addition, we delineated the in vivo pharmacokinetic profile and pancreas distribution of RC-106 in male CD-1 mice. Results: Panc-1, Capan-1, and Capan-2 express both SRs. RC-106 exerts an antiproliferative and pro-apoptotic effect in all examined cell lines. Cells exposure to RC-106 induces the increase of the expression of ER-UPR related proteins, and the inhibition of proteasome activity. Moreover, RC-106 is able to decrease PC cell lines motility. The in vivo results show that RC-106 is more concentrated in pancreas than plasma. Conclusion: Overall, our data evidenced that the pan-SR modulator RC-106 is an optimal candidate for in vivo studies in animal models of PC.

Sigma Receptors as Endoplasmic Reticulum Stress "Gatekeepers" and their Modulators as Emerging New Weapons in the Fight Against Cancer

Despite the interest aroused by sigma receptors (SRs) in the area of oncology, their role in tumor biology remains enigmatic. The predominant subcellular localization and main site of activity of SRs are the endoplasmic reticulum (ER). Current literature data, including recent findings on the sigma 2 receptor subtype (S2R) identity, suggest that SRs may play a role as ER stress gatekeepers. Although SR endogenous ligands are still unknown, a wide series of structurally unrelated compounds able to bind SRs have been identified. Currently, the identification of novel antiproliferative molecules acting via SR interaction is a challenging task for both academia and industry, as shown by the fact that novel anticancer drugs targeting SRs are in the preclinical-stage pipeline of pharmaceutical companies (i.e., Anavex Corp. and Accuronix). So far, no clinically available anticancer drugs targeting SRs are still available. The present review focuses literature advancements and provides a state-of-the-art overview of SRs, with emphasis on their involvement in cancer biology and on the role of SR modulators as anticancer agents. Findings from preclinical studies on novel anticancer drugs targeting SRs are presented in brief.

PEG 400/Cerium Ammonium Nitrate Combined with Microwave-Assisted Synthesis for Rapid Access to Beta-Amino Ketones. An Easy-to-Use Protocol for Discovering New Hit Compounds

Compound libraries are important requirement in target-based drug discovery. In the present work, a small focused compound library based on β-aminoketone scaffold has been prepared combining microwave-assisted organic synthesis (MAOS) with polymer-assisted solution phase synthesis (PASPS) and replacing reaction workup standard purification procedures with solid phase extraction (SPE). Specifically, the effects of solvent, such as dioxane, dimethylformamide (DMF), polyethylene glycol 400 (PEG 400), temperature, irradiation time, stoichiometric ratio of reagents, and catalysts (HCl, acetic acid, cerium ammonium nitrate (CAN)) were investigated to maximize both conversion and yield. The optimized protocol generally afforded the desired products in satisfying yields and purities. The designed library is a part of our current research on sigma 1 receptor modulators, a valuable tool for the identification of novel potential hit compounds.

Novel Sigma-1 receptor antagonists: from opioids to small molecules: what is new?

Sigma-1 (σ1) receptor has been identified as a chaperone protein that interacts with other proteins, such as N-methyl-D-aspartate (NMDA) and opioid receptors, modulating their activity. σ1 receptor antagonists have been developed to obtain useful compounds for the treatment of psychoses, pain, drug abuse and cancer. Some interesting compounds such as E-5842 (5) and MS-377 (24), haloperidol and piperazine derivatives, respectively, were endowed with high affinity for σ1 receptors (Ki σ1 = 4 and 73 nM; Ki σ2 = 220 and 6900, respectively). They were developed for the treatment of psychotic disorders and 5 also underwent Phase II clinical trials suggesting interesting potential therapeutic applications. Here, σ1 receptor antagonists have been grouped based on chemical structure and reviewed according to structure-activity relationship and potential therapeutic role.

Are sigma receptor modulators a weapon against multiple sclerosis disease?

Effective therapies for multiple sclerosis (MS) are still missing. This neurological disease affects more than 2.5 million people worldwide. To date, biological immunomodulatory drugs are effective and safe during short-term treatment, but they are suitable only for parenteral administration and they are expensive. Accordingly, academic and industrial environments are still focusing their efforts toward the development of new MS drugs. Considering that neurodegeneration is a contributory factor in the onset of MS, herein we will focus on the crucial role played by sigma 1 receptors (S1Rs) in MS. A pilot study was performed, evaluating the effect of the S1R agonist (R)-RC33 on rat dorsal root ganglia experimental model. The encouraging results support the potential of S1R agonists for MS treatment.

Sigma Receptor (σR) Ligands with Antiproliferative and Anticancer Activity

Sigma receptor (σR) ligands have proven to be useful as cancer diagnostics and anticancer therapeutics and their ligands have been developed as molecular probes in oncology. Moreover, various σR ligands generate cancer cell death in vitro and in vivo. These σR ligands have exhibited promising results against numerous human and rodent cancers and are investigated under preclinical and clinical study trials, indicating a new category of drugs in cancer therapy.

Synthesis and pharmacological evaluation of benzamide derivatives as potent and selective sigma-1 protein ligands

A series of novel benzamide-derived compounds was designed, synthesized and pharmacologically evaluated. Among all 37 synthesized compounds, two series were developed with the modulation of the nature, the position of atoms or groups on the benzamide scaffold, but also the nature of the amine group separated from the benzamide with 2, 3 or 4 methylene groups. In vitro competition binding assays against sigma proteins (sigma-1 S1R and sigma-2 S2R) revealed that most of them conferred S2R/S1R selectivity toward without cytotoxic effects on SY5Y cells, especially with the first series with compounds 7a-z. Some selected compounds were also evaluated for their agonist and antagonist activities on a panel of 40 receptors. Results showed the importance of the nature and the position with halogeno atom on the benzamide scaffold, the length chain but also the contribution of the hydrophobic part on the amine group. Among them, compounds 7i, w, y with Cl, CN or NO₂ groups at the 4-position of the benzamide scaffold showed excellent affinity for S1R (Ki = 1.2-3.6 nM), selectivity for S2R (Ki up to 1400 nM) and high selectivity index (IC_50(SY5Y)/Ki_(S1R) ratio from 28 000 to 83 000). Futhermore, these compounds presented an excellent safety profile over 40 other receptors. These derivatives will be selected for further biological investigations.

Are sigma modulators an effective opportunity for cancer treatment? A patent overview (1996-2016)

INTRODUCTION

Although several molecular targets against cancer have been identified, there is a continuous need for new therapeutic strategies. Sigma Receptors (SRs) overexpression has been recently associated with different cancer conditions. Therefore, novel anticancer agents targeting SRs may increase the specificity of therapies, overcoming some of the common drawbacks of conventional chemotherapy. Areas covered: The present review focuses on patent documents disclosing SR modulators with possible application in cancer therapy and diagnosis. The analysis reviews patents of the last two decades (1996-2016); patents were grouped according to target subtypes (S1R, S2R, pan-SRs) and relevant Applicants. The literature was searched through Espacenet, ISI Web, PatentScope and PubMed databases. Expert opinion: The number of patents related to SRs and cancer has increased in the last twenty years, confirming the importance of this receptor family as valuable target against neoplasias. Despite their short history in the cancer scenario, many SR modulators are at pre-clinical stage and one is undergoing a phase II clinical trial. SRs ligands may represent a powerful source of innovative antitumor therapeutics. Further investigation is needed for validating SR modulators as anti-cancer drugs. We strongly hope that this review could stimulate the interest of both Academia and pharmaceutical companies.

Recent advancements on the use of 2-methyltetrahydrofuran in organometallic chemistry

ABSTRACT

Since the introduction of 2-methyltetrahydrofuran as an useful alternative to the classical tetrahydrofuran, there has been a continuous interest in the synthetic community operating at academic and industrial towards it. In particular, the much higher stability that basic organometallic reagents display in 2-methyltetrahydrofuran makes it suitable for processes involving such sensitive species including asymmetric transformations. The easy formation of an azeotropic mixture with water, the substantial immiscibility with water, and the fact it derives from natural sources (corncobs or bagasse), allow to consider it in agreement with the Anastas' Geen Chemistry principles. In this minireview, selected examples of its employment in organometallic transformations ranging from carbanions to radical and transition metal-catalyzed processes are provided.

GRAPHICAL ABSTRACT