Samuele Maramai

Multifunctional cholinesterase and amyloid Beta fibrillization modulators. Synthesis and biological investigation.

In order to identify novel Alzheimers modifying pharmacological tools, we developed bis-tacrines bearing a peptide moiety for specific interference with surface sites of human acetylcholinesterase (hAChE) binding amyloid-beta (Aβ). Accordingly, compounds 2a-c proved to be inhibitors of hAChE catalytic and noncatalytic functions, binding the catalytic and peripheral sites, interfering with Aβ aggregation and with the Aβ self-oligomerization process (2a). Compounds 2a-c in complex with TcAChE span the gorge with the bis-tacrine system, and the peptide moieties bulge outside the gorge in proximity of the peripheral site. These moieties are likely responsible for the observed reduction of hAChE-induced Aβ aggregation since they physically hamper Aβ binding to the enzyme surface. Moreover, 2a was able to significantly interfere with Aβ self-oligomerization, while 2b,c showed improved inhibition of hAChE-induced Aβ aggregation.

Disease modifying anti-Alzheimer’s drugs: inhibitors of human cholinesterases interfering with β-amyloid aggregation

We recently described multifunctional tools (2a–c) as potent inhibitors of human Cholinesterases (ChEs) also able to modulate events correlated with Aβ aggregation. We herein propose a thorough biological and computational analysis aiming at understanding their mechanism of action at the molecular level.

Development and Pharmacological Characterization of Selective Blockers of 2-Arachidonoyl Glycerol Degradation with Efficacy in Rodent Models of Multiple Sclerosis and Pain

We report the discovery of compound 4a, a potent β-lactam-based monoacylglycerol lipase (MGL) inhibitor characterized by an irreversible and stereoselective mechanism of action, high membrane permeability, high brain penetration evaluated using a human in vitro blood-brain barrier model, high selectivity in binding and affinity-based proteomic profiling assays, and low in vitro toxicity. Mode-of-action studies demonstrate that 4a, by blocking MGL, increases 2-arachidonoylglycerol and behaves as a cannabinoid (CB1/CB2) receptor indirect agonist. Administration of 4a in mice suffering from experimental autoimmune encephalitis ameliorates the severity of the clinical symptoms in a CB1/CB2-dependent manner. Moreover, 4a produced analgesic effects in a rodent model of acute inflammatory pain, which was antagonized by CB1 and CB2 receptor antagonists/inverse agonists. 4a also relieves the neuropathic hypersensitivity induced by oxaliplatin. Given these evidence, 4a, as MGL selective inhibitor, could represent a valuable lead for the future development of therapeutic options for multiple sclerosis and chronic pain.

Discovery of potent inhibitors of human and mouse fatty acid amide hydrolases

Fatty acid amide hydrolase (FAAH, EC 3.5.1.99) is the main enzyme catabolizing endocannabinoid fatty acid amides. FAAH inactivation promotes beneficial effects upon pain and anxiety without the side effects accompanying agonists of type-1 cannabinoid receptors. Aiming at discovering new selective FAAH inhibitors, we developed a series of compounds (5a-u) characterized by a functionalized heteroaromatic scaffold. Particularly, 5c and 5d were identified as extremely potent, noncompetitive, and reversible FAAH inhibitors endowed with a remarkable selectivity profile and lacking interaction with the hERG channels. In vivo antinociceptive activity was demonstrated for 5c, 5d, and 5n at a dose much lower than that able to induce either striatal and limbic stereotypies or anxiolytic activity, thus outlining their potential to turn into optimum preclinical candidates. Aiming at improving pharmacokinetic properties and metabolic stability of 5d, we developed a subset of nanomolar dialyzable FAAH inhibitors (5v-z), functionalized by specific polyethereal lateral chains and fluorinated aromatic rings.

Selective kainate receptor (GluK1) ligands structurally based upon 1H-cyclopentapyrimidin-2,4(1H,3H)-dione: synthesis, molecular modeling, and pharmacological and biostructural characterization.

The physiological function of kainate receptors (GluK1-GluK5) in the central nervous system is not fully understood yet. With the aim of developing potent and selective GluK1 ligands, we have synthesized a series of new thiophene-based GluK1 agonists (6a-c) and antagonists (7a-d). Pharmacological evaluation revealed that they are selective for the GluK1 subunit, with 7b being the most subtype-selective ligand reported to date (GluK1 vs GluK3). The antagonist 7a was cocrystallized with the GluK1 ligand binding domain, and an X-ray crystallographic analysis revealed the largest flexibility in GluK1 ligand binding domain opening upon binding of a ligand seen to date. The results provide new insights into the molecular mechanism of GluK1 receptor ligand binding and pave the way to the development of new tool compounds for studying kainate receptor function.

Dopamine D3 Receptor Antagonists as Potential Therapeutics for the Treatment of Neurological Diseases

D3 receptors represent a major focus of current drug design and development of therapeutics for dopamine-related pathological states. Their close homology with the D2 receptor subtype makes the development of D3 selective antagonists a challenging task. In this review, we explore the relevance and therapeutic utility of D3 antagonists or partial agonists endowed with multireceptor affinity profile in the field of central nervous system disorders such as schizophrenia and drug abuse. In fact, the peculiar distribution and low brain abundance of D3 receptors make them a valuable target for the development of drugs devoid of motor side effects classically elicited by D2 antagonists. Recent research efforts were devoted to the conception of chemical templates possibly endowed with a multi-target profile, especially with regards to other G-protein-coupled receptors (GPCRs). A comprehensive overview of the recent literature in the field is herein provided. In particular, the evolution of the chemical templates has been tracked, according to the growing advancements in both the structural information and the refinement of the key pharmacophoric elements. The receptor/multireceptor affinity and functional profiles for the examined compounds have been covered, together with their most significant pharmacological applications.

A stereoselective approach to peptidomimetic BACE1 inhibitors.

Aiming at identifying new scaffolds to generate beta-secretase (BACE1) inhibitors we developed peptidomimetics based on a 1,4-benzodiazepine core (3a-d), their seco-analogs (4a-b), and linear analogs (5a-h), by stereoselective approaches. We herein discuss the synthesis, molecular modeling and in vitro studies for the newly developed ligands. Compounds 5c and 5h behaved as BACE1 inhibitors on the isolated enzyme and in cellular studies. Particularly, for its low molecular weight, inhibitor 5h is a prototypic hit to develop a series of BACE1 inhibitors more potent and active on whole-cells.

Identification of a novel arylpiperazine scaffold for fatty acid amide hydrolase inhibition with improved drug disposition properties

We herein describe the systematic approach used to develop new analogues of compound 2, recently identified as a potent and selective fatty acid amide hydrolase (FAAH) inhibitor. Aiming at identifying new scaffolds endowed with improved drug disposition properties with respect to the phenylpyrrole-based lead, we subjected it to two different structural modification strategies. This process allowed the identification of derivatives 4b and 5c as potent, reversible and non-competitive FAAH inhibitors.

Phenylpyrrole-based HDAC inhibitors: synthesis, molecular modeling and biological studies

AIM Histone deacetylases (HDACs) regulate the expression and activity of numerous proteins involved in the initiation and progression of cancer. Currently, three hydroxamate-containing HDAC pan-inhibitors have been approved as antitumor agents. RESULTS We herein present the development of a series of novel phenylpyrrole-based derivatives stemmed from combined computational and medicinal chemistry efforts to rationally modulate HDAC1/6 isoform selectivity. In vitro activity on HDAC1 and HDAC6 isoforms and the effects of selected analogs on histone H3 and α-tubulin acetylation levels were determined. Cell-based data evidenced, for selected compounds, a promising antitumor potential and low toxicity on normal cells. CONCLUSION The newly developed compounds represent a valuable starting point for the development of novel anticancer agents.

Harnessing the pyrroloquinoxaline scaffold for FAAH and MAGL interaction: definition of the structural determinants for enzyme inhibition

This paper describes the development of piperazine and 4-aminopiperidine carboxamides/carbamates supported on a pharmacogenic pyrroloquinoxaline scaffold as inhibitors of the endocannabinoid catabolizing enzymes fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL). Structure–activity relationships and molecular modelling studies allowed the definition of the structural requirements for dual FAAH/MAGL inhibition and led to the identification of a small set of derivatives (compounds 5e, i, k, m) displaying a balanced inhibitory profile against both enzymes, with compound 5m being the frontrunner of the subset. Favorable calculated physico-chemical properties suggest further investigation for specific analogues.