BS148 Reduces the Aggressiveness of Metastatic Melanoma via Sigma-2 Receptor Targeting.

The management of advanced-stage melanoma is clinically challenging, mainly because of its resistance to the currently available therapies. Therefore, it is important to develop alternative therapeutic strategies. The sigma-2 receptor (S2R) is overexpressed in proliferating tumor cells and represents a promising vulnerability to target. Indeed, we have recently identified a potent S2R modulator (BS148) that is effective in melanoma. To elucidate its mechanism of action, we designed and synthesized a BS148 fluorescent probe that enters SK-MEL-2 melanoma cells as assessed using confocal microscopy analysis. We show that S2R knockdown significantly reduces the anti-proliferative effect induced by BS148 administration, indicating the engagement of S2R in BS148-mediated cytotoxicity. Interestingly, BS148 treatment showed similar molecular effects to S2R RNA interference-mediated knockdown. We demonstrate that BS148 administration activates the endoplasmic reticulum stress response through the upregulation of protein kinase R-like ER kinase (PERK), activating transcription factor 4 (ATF4) genes, and C/EBP homologous protein (CHOP). Furthermore, we show that BS148 treatment downregulates genes related to the cholesterol pathway and activates the MAPK signaling pathway. Finally, we translate our results into patient-derived xenograft (PDX) cells, proving that BS148 treatment reduces melanoma cell viability and migration. These results demonstrate that BS148 is able to inhibit metastatic melanoma cell proliferation and migration through its interaction with the S2R and confirm its role as a promising target to treat cancer.

Investigation of the effect of different linker chemotypes on the inhibition of histone deacetylases (HDACs).

Histone Deacetylases (HDACs) are among the most attractive and interesting targets in anticancer drug discovery. The clinical relevance of HDAC inhibitors (HDACIs) is testified by four FDA-approved drugs for cancer treatment. However, one of the main drawbacks of these drugs resides in the lack of selectivity against the different HDAC isoforms, resulting in severe side effects. Thus, the identification of selective HDACIs represents an exciting challenge for medicinal chemists. HDACIs are composed of a cap group, a linker region, and a metal-binding group interacting with the catalytic zinc ion. While the cap group has been extensively investigated, less information is available about the effect of the linker on isoform selectivity. To this aim, in this work, we explored novel linker chemotypes to direct isoform selectivity. A small library of 25 hydroxamic acids with hitherto unexplored linker chemotypes was prepared. In vitro tests demonstrated that, depending on the linker type, some candidates selectively inhibit HDAC1 over HDAC6 isoform or vice versa. Docking calculations were performed to rationalize the effect of the novel linker chemotypes on biologic activity. Moreover, four compounds were able to increase the levels of acetylation of histone H3 or tubulin. These compounds were also assayed in breast cancer MCF7 cells to test their antiproliferative effect. Three compounds showed a significant reduction of cancer proliferation, representing valuable starting points for further optimization.

Exhaustive CoMFA and CoMSIA analyses around different chemical entities: a ligand-based study exploring the affinity and selectivity profiles of 5-HT1A ligands.

The 5-hydroxytryptamine (5-HT1A) receptors represent an attractive target in drug discovery. In particular, 5-HT1A agonists and partial agonists are deeply investigated for their potential role in the treatment of anxiety, depression, ischaemic brain disorder and more recently, of pain. On the other hand, 5-HT1A antagonists have been revealed promising compounds in cognition disorders and, lately, in cancer. Thus, the discovery of 5HT1A ligands is nowadays an appealing research activity in medicinal chemistry. In this work, Comparative Molecular Fields Analysis (CoMFA) and Comparative Molecular Similarity Index Analysis (CoMSIA) were applied on an in-house library of 5-HT1A ligands bearing different chemical scaffolds in order to elucidate their affinity and selectivity for the target. Following this procedure, a number of structural modifications have been drawn for the development of much more effective 5-HT1AR ligands. [Formula: see text].

Evaluation of stereo and chemical stability of chiral compounds.

A stopped-flow bidimensional recycle HPLC (sf-BD-rHPLC) configuration has been used to investigate simultaneously the stereo and chemical stability of labile chiral compounds. The single enantiomers of a racemate can be separated on chiral column (first dimension) and each one can be trapped in the achiral column (second dimension) that works as reactor.By filling the achiral column with the appropriate aqueous buffers it is possible to evaluate the stability of the trapped enantiomer toward aqueous buffer itself. It was possible to recycle the reaction products formed in the chiral column (first dimension) where they are separated by a second six valve port. The reaction rate constants were calculated for the different processes occurred in the achiral column by means of corresponding peak areas. The method was applied to a pharmacological active compound: (±)7-chloro-5-ethyl-3-methyl-3,4-dihydro-2H-benzo[1,2,4]thiadiazine 1,1-dioxide ((±)-1) to evaluate enantiostability and hydrolysis in conditions similar to those of biological fluid. A classical batchwise kinetic method was used to calculate rate constants of hydrolysis and enantiomerization at the same temperature and in the same solvents used in sf-BD-rHPLC. The good agreement of the results obtained validate the novel procedure developed. Furthermore, the results generated off-line were used to determine the influence of solvents on the racemization of (±)-1.

Discovery of a new series of 5-HT1A receptor agonists.

Starting from compounds previously identified as alpha(1)-adrenoceptor antagonists that were also found to bind to the 5-HT(1A) receptor, in an attempt to separate the two activities, a new series of 5-HT(1A) receptor agonists was identified and shown to have high potency and/or high selectivity. Of these, compound 13, which combines high selectivity (5-HT(1A)/alpha(1)=151) and good agonist potency (pD(2)=7.82; E(max)=76), was found to be the most interesting.

Spiroxatrine derivatives towards 5-HT1A receptor selectivity.

BACKGROUND: In our previous work, spiroxatrine was taken as reference compound to develop selective NOP ligands. Therefore, several triazaspirodecanone derivatives were synthesized. Here, we verify their selectivity towards other 5-HT1 receptor subtypes and with respect to α2-AR (Adrenergic Receptors). METHODS: Binding affinities were determined on cells expressing human cloned receptors for 5-HT1A/B/D and α2A/B/C subtypes. The Ki values were determined for those with at least 50% radioligand inhibition. RESULTS: All our derivatives show a moderate affinity for α2 subtypes, spanning from 5 to 7.5 pKi values. Moreover, they show affinity values in a µM-nM range at the 5-HT1A receptor, while they are practically inactive at 5-HT1B and 5-HT1D subtypes. Compound 11, the best of the series, has a 5-HT1A pKi value of 8.43 similar to spiroxatrine but, notably, it has a 5-HT1A favorable selectivity ratio of 52, 8 and 29, respectively over α2A, α2B and α2C adrenoceptor subtypes. CONCLUSIONS: In this SAR study, a 5-HT1A selective ligand has been identified in which a tetralone moiety replaced the 1,4-benzodioxane of spiroxatrine and the methylene linker to the triazaspirodecanone portion was maintained in position 2.

Novel Dithiolane-Based Ligands Combining Sigma and NMDA Receptor Interactions as Potential Neuroprotective Agents.

Sigma receptors (SRs) are recognized as valuable targets for the treatment of neurodegenerative disorders. A series of novel SRs ligands were designed by combining key pharmacophoric amines (i.e., benzylpiperidine or benzylpiperazine) with new 1,3-dithiolane-based heterocycles and their bioisosters. The new compounds exhibited a low nanomolar affinity for sigma-1 and sigma-2 receptors. Five selected compounds were evaluated for their neuroprotective capacity on SH-SY5Y neuroblastoma cell line. They were able to counteract the neurotoxicity induced by rotenone, oligomycin and NMDA. Competition studies with PB212, a S1R antagonist, confirmed the involvement of S1R in neuroprotection from the oxidative stress induced by rotenone. Electrophysiological experiments performed on cortical neurons in culture highlighted the compounds ability to reduce NMDA-evoked currents, suggesting a negative allosteric modulator activity toward the NMDA receptor. Altogether these results qualify our novel dithiolane derivatives as potential agents for fighting neurodegeneration.

Identification of a Potent and Selective 5-HT1A Receptor Agonist with In Vitro and In Vivo Antinociceptive Activity.

Opioids are the gold standard drugs for the treatment of acute and chronic severe pain, although their serious side effects constitute a big limitation. In the search for new and safer drugs, 5-HT1AR agonists are emerging as potential candidates in pain relief therapy. In this work, we evaluated the affinity and activity of enantiomers of the two newly synthesized, potent 5-HT1AR agonists N-[(2,2-diphenyl-1,3-dioxolan-4-yl)methyl]-2-[2-(pyridin-4-yl)phenoxy]ethan-1-ammonium hydrogenoxalate (rac-1) and N-((2,2-diphenyl-1,3-dioxolan-4-yl)methyl)-2-(2-(1-methyl-1H-imidazol-5-yl)phenoxy)ethan-1-ammonium hydrogenoxalate (rac-2) in vitro and in vivo. The role of chirality in the interaction with 5-HT1AR was evaluated by molecular docking. The activity of the rac-1 was tested in mouse models of acute pain (hot plate) and severe tonic nociceptive stimulation (intraplantar formalin test). Rac-1 was active in the formalin test with a reduction in paw licking in both phases at 10 mg/kg, and its effect was abolished by the selective 5-HT1AR antagonist, WAY-100635. The eutomer (S)-1, but not the racemate, was active during the hot plate test at 10 and 20 mg/kg, and this effect was abolished by 30 min treatment with WAY-100635 at 30 min. Similarly to 8-OH-DPAT, (S)-1 evoked a slow outward current and depressed spontaneous glutamatergic transmission in superficial dorsal horn neurons, more effectively than rac-1. The eutomer (S)-1 showed promising developability properties, such as high selectivity over 5-HT subtypes, no interaction with the µ receptors, and low hepato- and cardiotoxicity. Therefore, (S)-1 may represent a potential candidate for the treatment of acute and chronic pain without having the adverse effects that are commonly associated with the classic opioid drugs.

1,3-Dioxane as a scaffold for potent and selective 5-HT1AR agonist with in-vivo anxiolytic, anti-depressant and anti-nociceptive activity.

A series of compounds generated by ring expansion/opening and molecular elongation/simplification of the 1,3-dioxolane scaffold were prepared and tested for binding affinity at 5-HT1AR and α1 adrenoceptors. The compounds with greater affinity were selected for further functional studies. N-((2,2-diphenyl-1,3-dioxan-5-yl)methyl)-2-(2-methoxyphenoxy)ethan-1-ammonium hydrogen oxalate (12) emerged as highly potent full agonist at the 5-HT1AR (pKi 5-HT1A = 8.8; pD2 = 9.22, %Emax = 92). The pharmacokinetic data in rats showed that the orally administered 12 has a high biodistribution in the brain compartment. Thus, 12 was further investigated in-vivo, showing an anxiolytic and antidepressant effect. Moreover, in the formalin test, 12 was able to decrease the late response to the noxious stimulus, indicating a potential use in the treatment of chronic pain.

Synthesis and biological evaluation of 1,3-dioxolane-based 5-HT1A receptor agonists for CNS disorders and neuropathic pain.

AIM: Targeting 5-HT1A receptor (5-HT1AR) as a strategy for CNS disorders and pain control. METHODOLOGY: A series of 1,3-dioxolane-based 2-heteroaryl-phenoxyethylamines was synthesized by a convergent approach and evaluated at α1-adrenoceptors and 5-HT1AR by binding and functional experiments. Absorption, distribution, metabolism, excretion and toxicity prediction studies were performed to explore the drug-likeness of the compounds. RESULTS & CONCLUSION: The most promising compound, the pyridin-4-yl derivative, emerged as a potent and selective 5-HT1AR agonist (pKi = 9.2; pD2 = 8.83; 5-HT1A/α1 = 135). In vitro it was able to permeate by passive diffusion MDCKII-MDR1 monolayer mimicking the blood-brain barrier and showed promising neuroprotective activity.

Synthesis, structural characterization and biological evaluation of 4'-C-methyl- and phenyl-dioxolane pyrimidine and purine nucleosides.

Nucleoside analogues play an important role in antiviral, antibacterial and antineoplastic chemotherapy. Herein we report the synthesis, structural characterization and biological activity of some 4'-C -methyl- and -phenyl dioxolane-based nucleosides. In particular, α and ß anomers of all natural nucleosides were obtained and characterized by NMR, HR-MS and X-ray crystallography. The compounds were tested for antimicrobial activity against some representative human pathogenic fungi, bacteria and viruses. Antitumor activity was evaluated in a large variety of human cancer cell-lines. Although most of the compounds showed non-significant activity, 23α weakly inhibited HIV-1 multiplication. Moreover, 22α and 32α demonstrated a residual antineoplastic activity, interestingly linked to the unnatural α configuration. These results may provide structural insights for the design of active antiviral and antitumor agents.

Synthesis, biological evaluation and molecular modeling of 1-oxa-4-thiaspiro- and 1,4-dithiaspiro[4.5]decane derivatives as potent and selective 5-HT1A receptor agonists.

Recently, 1-(1,4-dioxaspiro[4,5]dec-2-ylmethyl)-4-(2-methoxyphenyl)piperazine (1) was reported as a potent 5-HT1AR agonist with a moderate 5-HT1AR selectivity. In an extension of this work a series of derivatives of 1, obtained by combining different heterocyclic rings with a more flexible amine chain, was synthesized and tested for binding affinity and activity at 5-HT1AR and α1 adrenoceptors. The results led to the identification of 14 and 15 as novel 5-HT1AR partial agonists, the first being outstanding for selectivity (5-HT1A/α1d = 80), the latter for potency (pD2 = 9.58) and efficacy (Emax = 74%). Theoretical studies of ADME properties shows a good profile for the entire series and MDCKII-MDR1 cells permeability data predict a good BBB permeability of compound 15, which possess a promising neuroprotective activity. Furthermore, in mouse formalin test, compound 15 shows a potent antinociceptive activity suggesting a new strategy for pain control.

Structure-Activity Relationships within a Series of σ1 and σ2 Receptor Ligands: Identification of a σ2 Receptor Agonist (BS148) with Selective Toxicity against Metastatic Melanoma.

A new series of spirocyclic σ receptor (σR) ligands were prepared and studied. Most were found to have a high affinity and selectivity for σ1 R; three compounds were shown to be σ1 R agonists, while another proved to be the only σ1 R antagonist. Only one of the σ1 R agonists (BS148) also exhibited σ2 R selectivity and was able to inhibit the growth of metastatic malignant melanoma cell lines without affecting normal human melanocytes. The antiproliferative activity of this compound suggested an σ2 R agonist profile. Further, preliminary investigations indicated that the mechanism of metastatic malignant melanoma cell death induced by BS148 is due, at least in part, to apoptosis.

Scouting new sigma receptor ligands: Synthesis, pharmacological evaluation and molecular modeling of 1,3-dioxolane-based structures and derivatives.

Herein we report the synthesis and biological activity of new sigma receptor (σR) ligands obtained by combining different substituted five-membered heterocyclic rings with appropriate σR pharmacophoric amines. Radioligand binding assay, performed on guinea pig brain membranes, identified 25b (1-(1,4-dioxaspiro[4.5]decan-2-ylmethyl)-4-benzylpiperazine) as the most interesting compound of the series, displaying high affinity and selectivity for σ1R (pKiσ1 = 9.13; σ1/σ2 = 47). The ability of 25b to modulate the analgesic effect of the κ agonist (-)-U-50,488H and µ agonist morphine was evaluated in vivo by radiant heat tail-flick test. It exhibited anti-opioid effects on both κ and µ receptor-mediated analgesia, suggesting an agonistic behavior at σ1R. Docking studies were performed on the theoretical σ1R homology model. The present work represents a new starting point for the design of more potent and selective σ1R ligands.

Synthesis and structure-activity relationships of 1-aralkyl-4-benzylpiperidine and 1-aralkyl-4-benzylpiperazine derivatives as potent sigma ligands.

In the attempt to define more accurately structure-affinity relationships for sigma(1) and sigma(2) ligands, we synthesized and tested on sigma subtype receptors a series of aralkyl derivatives of 4-benzylpiperidine, in which the effect of modifications on the aralkyl moiety was studied in a systematic way. The affinity of the compounds here described varied to a great extent, with a sigma(2)/sigma(1) selectivity ranging from 0.1 to 9. Thus, to confirm the ability of the piperazine derivative to bind to sigma(1) receptors in a different way than piperidines, we synthesized and tested a series of piperazine compounds; the comparison of their affinity with that of the corresponding piperidines strongly supports the possibility of a different binding mode. While the compounds here described are on the whole selective for sigma vs serotonin 5-HT(1A) and dopamine D(2) receptors, 9aa, 9ba and 9ab possess a remarkable affinity for both sigma and 5-HT(1A) receptors, with K(i) in the nanomolar range, and are selective with respect to D(2) receptors. They displayed also a partial agonist profile in a human 5-HT(1A) [(35)S]GTP gamma S binding assay, suggesting their potential use as atypical antipsychotic agents.

Synthesis and Structure-Activity Relationships of Triazaspirodecanone Derivatives as Nociceptin/Orphanin FQ Receptor Ligands.

Several spiroxatrine derivatives were synthesized and evaluated as potential NOP receptor ligands. Structural modifications of the 1,4-benzodioxane moiety of spiroxatrine have been the focus of this research project. The structure-activity relationships that emerged indicate that the presence of an H-bond donor group (hydroxyl group) is more favorable for NOP activity when it is positioned α with respect to the CH2 linked to the 1-phenyl-1,3,8-triaza-spiro[4.5]decan-4-one portion. Moreover, cis diastereoisomers of the hydroxyl derivatives4 and 22 show a moderately higher degree of stereoselectivity than trans isomers. In particular, the spiropiperidine derivative cis-4 has submicromolar agonistic activity, and it will be the reference compound for the design and synthesis of new NOP agonists.

1,3-dioxolane-based ligands as a novel class of alpha1-adrenoceptor antagonists.

1,3-Dioxolane-based compounds (2-14) were synthesized, and the pharmacological profiles at alpha(1)-adrenoceptor subtypes were assessed by functional experiments in isolated rat vas deferens (alpha(1A)), spleen (alpha(1B)), and aorta (alpha(1D)). Compound 9, with a pA(2) of 7.53, 7.36, and 8.65 at alpha(1A), alpha(1B), and alpha(1D), respectively, is the most potent antagonist of the series, while compound 10 with a pA(2) of 8.37 at alpha(1D) subtype and selectivity ratios of 162 (alpha(1D)/alpha(1A)) and 324 (alpha(1D)/alpha(1B)) is the most selective. Binding assays in CHO cell membranes expressing human cloned alpha(1)-adrenoceptor subtypes confirm the pharmacological profiles derived from functional experiments, although the selectivity values are somewhat lower. Therefore, it is concluded that 1,3-dioxolane-based ligands are a new class of alpha(1)-adrenoceptor antagonists.

Imidazoline binding sites (IBS) profile modulation: key role of the bridge in determining I1-IBS or I2-IBS selectivity within a series of 2-phenoxymethylimidazoline analogues.

The alpha- and beta-methyl derivatives of 2-phenylethylimidazoline (compounds 7 and 8) and the corresponding enantiomers were prepared and tested with the purpose of studying the role played by the ethylene bridge in modulating I(1)- and I(2)-IBS selectivity. The alpha-methylation appeared to be extremely critical regarding the affinity and selectivity for the I1-IBS subtypes (I1/I2 = 186 for imidazoline 7) and the stereospecificity of interaction (eudismic ratio (S)-(-)-7/(R)-(+)-7 = 5888). Instead, even if in a more limited fashion, the -methylation tended toward I2-IBS selectivity (I2/I1 = 50 for imidazoline 8). The unsubstituted compound 4 (I2/I1 = 1479) proved to be considerably more potent and selective with respect to I2-IBS subtypes.

Alpha2-adrenoreceptors profile modulation and high antinociceptive activity of (S)-(-)-2-[1-(biphenyl-2-yloxy)ethyl]-4,5-dihydro-1H-imidazole.

A number of derivatives structurally related to cirazoline (1) were synthesized and studied with the purpose of modulating alpha2-adrenoreceptors selectivity versus both alpha1-adrenoreceptors and I2 imidazoline binding sites. The most potent alpha2-agonist was 2-[1-(biphenyl-2-yloxy)ethyl]-4,5-dihydro-1H-imidazole (7), whose key pharmacophoric features closely matched those found in the alpha2-agonist 2-(3-exo-(3-phenylprop-1-yl)-2-exo-norbornyl)amino-2-oxazoline (15). (S)-(-)-7 was the most potent of the two enantiomers, confirming the stereospecificity of the interaction with alpha2-adrenoreceptors. This eutomer was tested on two algesiometric paradigms and, because of the interaction with alpha2-adrenoreceptors, showed a potent and long-lasting antinociceptive activity, since it was abolished by the selective alpha2-antagonist RX821002.

Development, validation and application of an LC-MS/MS bioanalytical method for the quantification of GF449, a novel 5-HT1A agonist, in rat plasma and brain.

We have recently reported a novel class of selective 5-HT1A agonists among which GF449 emerged for its high potency and almost full agonist activity (pKi 5-HT1A = 8.8; pD2 = 9.22, %Emax = 91.6). In order to quantify GF449 in rat plasma and brain, a sensitive LC-MS/MS method was developed and validated. Solid phase extraction (SPE) or a combined protein precipitation SPE permitted an efficient analyte recovery and sample clean-up. Multiple reaction monitoring (MRM) was used to track both GF449 and its internal standard (IS), MM189. GF449 was determined and quantitated to nanomolar concentrations in both plasma and brain matrix (LOQs = 0.0025 nmol/mL). Specificity was ensured using three further MRM qualifier transitions for both analyte and IS. Linearity was found in the range of 0.0025 nmol/mL to 1.00 nmol/mL (R(2) = 0.9965) and from 0.0025 nmol/mL to 50 nmol/mL (R(2) = 0.9999) for plasma and brain respectively. Intraday trueness ranged from 94.0% to 117.5% for brain and from 93.7% to 108.1% for plasma, while precision values were within 3.0% - 6.7% and 2.5% - 9.2% for plasma and brain respectively. The interday trueness of plasma ranged from 89.6% to 107.7% and the precision values (CV%) ranged from 4.6% to 7.5%. Interday trueness and precision (CV%) of the brain ranged from 94.3% to 101.2% and from 1.6% to 11.5% respectively. The method was validated in accordance with the EMEA guidelines and was successfully applied to plasma and brain samples obtained from rats treated with a 10 mg/kg single oral dose of GF449, thus demonstrating its applicability to preclinical pharmacokinetic studies.