Marco Catto

Discovery of a novel class of potent coumarin monoamine oxidase B inhibitors: development and biopharmacological profiling of 7-[(3-chlorobenzyl)oxy]-4-[(methylamino)methyl]-2H-chromen-2-one methanesulfonate (NW-1772) as a highly potent, selective, reversible, and orally active monoamine oxidase B inhibitor.

In an effort to discover novel selective monoamine oxidase (MAO) B inhibitors with favorable physicochemical and pharmacokinetic profiles, 7-[(m-halogeno)benzyloxy]coumarins bearing properly selected polar substituents at position 4 were designed, synthesized, and evaluated as MAO inhibitors. Several compounds with MAO-B inhibitory activity in the nanomolar range and excellent MAO-B selectivity (selectivity index SI > 400) were identified. Structure-affinity relationships and docking simulations provided valuable insights into the enzyme-inhibitor binding interactions at position 4, which has been poorly explored. Furthermore, computational and experimental studies led to the identification and biopharmacological characterization of 7-[(3-chlorobenzyl)oxy]-4-[(methylamino)methyl]-2H-chromen-2-one methanesulfonate 22b (NW-1772) as an in vitro and in vivo potent and selective MAO-B inhibitor, with rapid blood-brain barrier penetration, short-acting and reversible inhibitory activity, slight inhibition of selected cytochrome P450s, and low in vitro toxicity. On the basis of this preliminary preclinical profile, inhibitor 22b might be viewed as a promising clinical candidate for the treatment of neurodegenerative diseases.

9,10-Anthraquinone hinders β-aggregation: How does a small molecule interfere with Aβ-peptide amyloid fibrillation?

Amyloid aggregation is linked to a number of neurodegenerative syndromes, the most prevalent one being Alzheimers disease. In this pathology, the β‐amyloid peptides (Aβ) aggregate into oligomers, protofibrils, and fibrils and eventually into plaques, which constitute the characteristic hallmark of Alzheimers disease. Several low‐molecular‐weight compounds able to impair the Aβ aggregation process have been recently discovered; yet, a detailed description of their interactions with oligomers and fibrils is hitherto missing. Here, molecular dynamics simulations are used to investigate the influence of two relatively similar tricyclic, planar compounds, that is, 9, 10‐anthraquinone (AQ) and anthracene (AC), on the early phase of the aggregation of the Aβ heptapeptide segment H14QKLVFF20, the hydrophobic stretch that promotes the Aβ self‐assembly. The simulations show that AQ interferes with β‐sheet formation more than AC. In particular, AQ intercalates into the β‐sheet because polar interactions between the compound and the peptide backbone destabilize the interstrand hydrogen bonds, thereby favoring disorder. The thioflavin T‐binding assay indicates that AQ, but not AC, sensibly reduces the amount of aggregated Aβ1–40 peptide. Taken together, the in silico and in vitro results provide evidence that structural perturbations by AQ can remarkably affect ordered oligomerization. Moreover, the simulations shed light at the atomic level on the interactions between AQ and Aβ oligomers, providing useful insights for the design of small‐molecule inhibitors of aggregation with therapeutic potential in Alzheimers disease.

Applicability Domain for QSAR models: where theory meets reality

Quantitative Structure-Activity Relationships are widely acknowledged predictive methods employed, for years, in organic and medicinal chemistry. More recently, they have assumed a central role also in the context of the explorative toxicology for the protection of environment and human health. However, their real-life application has not been always enthusiastically welcomed, being often retrospectively used and, thus, of limited importance for prospective goals. The need of making more trustable predictions has thus addressed studies on the so-called Applicability Domain, which represents the chemical space from which a model is derived and where a prediction is considered to be reliable. In the present study, the authors survey a number of approaches used to build the Applicability Domain. In particular, they will focus on strategies based on: a) physico-chemical, b) structural and c) response domains. Moreover, some examples integrating different strategies will be also discussed to meet the needs of both model developers and downstream users. KeyWoRDS Applicability Domain, Interpolation Space, QSAR, Similarity, Structural Fragments

Design, Synthesis, and Biological Evaluation of Coumarin Derivatives Tethered to an Edrophonium‐like Fragment as Highly Potent and Selective Dual Binding Site Acetylcholinesterase Inhibitors

A large series of substituted coumarins linked through an appropriate spacer to 3‐hydroxy‐N,N‐dimethylanilino or 3‐hydroxy‐N,N,N‐trialkylbenzaminium moieties were synthesized and evaluated as acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitors. The highest AChE inhibitory potency in the 3‐hydroxy‐N,N‐dimethylanilino series was observed with a 6,7‐dimethoxy‐3‐substituted coumarin derivative, which, along with an outstanding affinity (IC50=0.236 nM) exhibits excellent AChE/BChE selectivity (SI>300 000). Most of the synthesized 3‐hydroxy‐N,N,N‐trialkylbenzaminium salts display an AChE affinity in the sub‐nanomolar to picomolar range along with excellent AChE/BChE selectivities (SI values up to 138 333). The combined use of docking and molecular dynamics simulations permitted us to shed light on the observed structure–affinity and structure–selectivity relationships, to detect two possible alternative binding modes, and to assess the critical role of π–π stacking interactions in the AChE peripheral binding site.

Design, Synthesis, and Biological Evaluation of Imidazolyl Derivatives of 4,7-Disubstituted Coumarins as Aromatase Inhibitors Selective over 17-α-Hydroxylase/C17-20 Lyase

The design, synthesis, and biological evaluation of a series of new aromatase (AR, CYP19) inhibitors bearing an imidazole ring linked to a 7-substituted coumarin scaffold at position 4 (or 3) are reported. Many compounds exhibited an aromatase inhibitory potency in the nanomolar range along with a high selectivity over 17-α-hydroxylase/C17-20 lyase (CYP17). The most potent AR inhibitor was the 7-(3,4-difluorophenoxy)-4-imidazolylmethyl coumarin 24 endowed with an IC(50) = 47 nM. Docking simulations on a selected number of coumarin derivatives allowed the identification of the most important interactions driving the binding and clearly indicated the allowed and disallowed regions for appropriate structural modifications of coumarins and closely related heterocyclic molecular scaffolds.

Homo- and hetero-bivalent edrophonium-like ammonium salts as highly potent, dual binding site AChE inhibitors

A number of mono- and bis-quaternary ammonium salts, containing edrophonium-like and coumarin moieties tethered by an appropriate linker, proved to be highly potent and selective dual binding site acetylcholinesterase inhibitors with good selectivity over butyrylcholinesterase. Homobivalent bis-quaternary inhibitors 11 and 12, differing by only one methylene unit in the linker, were the most potent and selective inhibitors exhibiting a sub-nanomolar affinity (IC(50)=0.49 and 0.17 nM, respectively) and a high butyryl-/acetylcholinesterase affinity ratio (SI=1465 and 4165, respectively). The corresponding hetero-bivalent coumarinic inhibitors 13 and 14 were also endowed with excellent inhibitory potency but a lower AChE selectivity (IC(50)=2.1 and 1.0 nM, and SI=505 and 708, respectively). Docking simulations enabled clear interpretation of the structure-affinity relationships and detection of key binding interactions at the primary and peripheral AChE binding sites.

Design, synthesis and biological evaluation of coumarin alkylamines as potent and selective dual binding site inhibitors of acetylcholinesterase.

Acetylcholinesterase inhibitors (AChEIs) are currently the drugs of choice, although only symptomatic and palliative, for the treatment of Alzheimers disease (AD). Donepezil is one of most used AChEIs in AD therapy, acting as a dual binding site, reversible inhibitor of AChE with high selectivity over butyrylcholinesterase (BChE). Through a combined target- and ligand-based approach, a series of coumarin alkylamines matching the structural determinants of donepezil were designed and prepared. 6,7-Dimethoxycoumarin derivatives carrying a protonatable benzylamino group, linked to position 3 by suitable linkers, exhibited fairly good AChE inhibitory activity and a high selectivity over BChE. The inhibitory potency was strongly influenced by the length and shape of the spacer and by the methoxy substituents on the coumarin scaffold. The inhibition mechanism, assessed for the most active compound 13 (IC(50) 7.6 nM) resulted in a mixed-type, thus confirming its binding at both the catalytic and peripheral binding sites of AChE.

Targeting monoamine oxidases with multipotent ligands: an emerging strategy in the search of new drugs against neurodegenerative diseases.

The socioeconomic burden of multi-factorial pathologies, such as neurodegenerative diseases (NDs), is enormous worldwide. Unfortunately, no proven disease-modifying therapy is available yet and in most cases (e.g., Alzheimers and Parkinsons disease) the approved drugs exert only palliative and symptomatic effects. Nowadays, an emerging strategy for the discovery of disease-modifying drugs is based on the multi-target directed ligand (MTDL) design, an innovative shift from the traditional approach one-drug-one-target to the more ambitious one-drug-more-targets goal. Herein, we review the discovery strategy, the mechanism of action and the biopharmacological evaluation of multipotent ligands exhibiting monoamine oxidase (MAO) inhibition as the core activity with a potential for the treatment of NDs. In particular, MAO inhibitors exhibiting additional acetylcholinesterase (AChE) or nitric oxide synthase (NOS) inhibition, or ion chelation/antioxidant-radical scavenging/anti-inflammatory/A2A receptor antagonist/APP processing modulating activities have been thoroughly examined.

CE can identify small molecules that selectively target soluble oligomers of amyloid β protein and display antifibrillogenic activity

Soluble and toxic oligomers of amyloid β (Aβ) protein have been identified as the true neurotoxic species involved in Alzheimers disease and considering them as targets to inhibit Aβ aggregation might have a therapeutic value. We previously set up a CE method that enables the separation and quantification of transient oligomers of Aβ protein‐containing 42 amino acids (Aβ1–42) along the pathway leading to fibrils and we now demonstrate how this method can be successfully applied to examine the in vitro inhibitory effects of small molecules on Aβ oligomerization. To this end, we investigated mitoxantrone and pixantrone, two well‐known anticancer drugs, as well as suramin and a suramin‐like compound. By using CE, it is here shown how mitoxantrone and pixantrone either reduce or block Aβ1–42 oligomerization, while Thioflavin T spectrofluorimetric assay and transmission electron microscopy demonstrate how these two compounds also display antifibrillogenic activity. Interestingly, in vitro cell viability experiments indicated that pixantrone significantly reduces Aβ1–42 neurotoxicity.

Quinolizidinyl derivatives of bi- and tricyclic systems as potent inhibitors of acetyl- and butyrylcholinesterase with potential in Alzheimer's disease

On the pattern of the potent and selective butyrylcholinesterase (BChE) inhibitors ethopropazine and Astra1397, sets of quinolizidinyl derivatives of bi- and tricyclic (hetero)aromatic systems were studied as dual, or BChE-selective inhibitors. All compounds exhibited activity against both cholinesterases, but inhibition of BChE was generally stronger, with submicromolar IC50 values for most of them (e.g. 15: IC50 versus BChE=0.15 μM; SI=47). However, in a subset of quinolizidinyl derivatives of 6-hydroxycoumarin an inverted selectivity for acetylcholinesterase (AChE) was observed (e.g. 46: IC50 versus AChE=0.35 μM; SI=0.06). Docking studies furnished a sound interpretation of the observed different enzyme activity. Several of the studied compounds have shown, in the past, additional pharmacological properties (as antagonism on presynaptic muscarinic autoreceptor; inhibition of enkephaline aminopeptidase and antipsychotic activity) of some relevance in Alzheimers disease, and may, therefore, represent hits for the development of interesting single-entity multi-target drugs.