Identification of non-furan containing A2A antagonists using database mining and molecular similarity approaches

Synthesis, characterization, and in silico studies of 1,8-naphthyridine derivatives as potential anti-Parkinson's agents

1,8-Naphthyridine scaffold is a nitrogen-containing heterocyclic compound known for its versatile biological activities. The structure-activity relationship (SAR) has shown that modification at the 3rd position of the nucleus with various secondary amines enhances the binding efficiency and potency towards the Adenosine receptor (A2A type). In this paper, we have reported some newly synthesized derivatives of 1,8- Naphthyridine, and the prepared compounds were assessed for their potential to constrain A2A receptors through molecular docking. Based on the SAR studies, modifications were done at the 3rd position of the nucleus by incorporating secondary amines. The synthesized compounds were characterized by FT-IR, ¹H and ¹³C NMR. All the synthesized compounds 10a-f and 13a-e showed good binding efficiency towards the A2A receptors and might act as an A2A receptor antagonist, as predicted by in-silico studies. 1-Ethyl-7-methyl-3-(pyrrolidine-1-carbonyl)-1,8-naphthyridine-4(1H)-one (10c) in first series showed the highest docking score of -8.407 and binding energy (MMGBSA dG bind) of -56.60 kcal/mol and N-(4-2-diethylaminoethoxyphenyl)-1-ethyl-7-methyl-4-oxo-1, 4, 4a, 8a- tetrahydro-1,8-naphthyridine-3-carboxamide (13b) showed the highest docking score of -8.562 and free binding energy (MMGBSA dG bind) score of -64.13 kcal/mol which was comparable to the bound ligand. MD simulations study also suggested that compounds 10c and 13b would form stable complex human A2A receptor. These findings need to be validated by further in vitro assays.Communicated by Ramaswamy H. Sarma.

X-Ray Crystallography and Free Energy Calculations Reveal the Binding Mechanism of A2A Adenosine Receptor Antagonists

We present a robust protocol based on iterations of free energy perturbation (FEP) calculations, chemical synthesis, biophysical mapping and X-ray crystallography to reveal the binding mode of an antagonist series to the A2A adenosine receptor (AR). Eight A2A AR binding site mutations from biophysical mapping experiments were initially analyzed with sidechain FEP simulations, performed on alternate binding modes. The results distinctively supported one binding mode, which was subsequently used to design new chromone derivatives. Their affinities for the A2A AR were experimentally determined and investigated through a cycle of ligand-FEP calculations, validating the binding orientation of the different chemical substituents proposed. Subsequent X-ray crystallography of the A2A AR with a low and a high affinity chromone derivative confirmed the predicted binding orientation. The new molecules and structures here reported were driven by free energy calculations, and provide new insights on antagonist binding to the A2A AR, an emerging target in immuno-oncology.

Antioxidant Properties of Synthesized Bicyclic Thiazolopyrimidine Derivatives as Possible Therapeutic Agents

Oxidant/antioxidant imbalance in the body has been implicated as one of the pathophysiological mechanisms leading to disease development. Therefore, we searched for a good antioxidant candidate that can be used as a therapeutic agent alone or in combination with other reported drugs. Earlier, we reported the A2A receptor antagonist properties of 7-Imino-3-substituted-2-thioxo-3,7-dihydro-2H-thiazolo[4,5-d]pyrimidin-6-yl)-urea derivatives (compounds 1–12) and the neuroprotective effect of compound 2. Therefore, in the present work, the antioxidant potential of compounds 1–12 was studied. Compounds 1–12 were screened using different (red/ox) tests, such as the Ferric Reducing Antioxidant Power (FRAP) assay, to determine total antioxidant activity, redox status tests (with and without prooxidants) such as Advanced Oxidation Protein Products (AOPP) and Total Oxidative Status (TOS) which measures H2O2 and lipid hydroperoxides, Paraoxonase-1 Enzyme Activity (PON1), Total SH-groups content, and Total Antioxidative Status (TAS) for antioxidant determination. The Prooxidative Score, Antioxidative Score, and Oxy Score were also calculated. From the obtained results, compounds 6 (8720 FRAP value and 39.31 Oxy Score) and 12 (7866 FRAP value and 36.41 Oxy Score) were found to possess significant antioxidant activity with reasonable potential for therapeutic activity.

Lewis acid activation of pyridines for nucleophilic aromatic substitution and conjugate addition

A clean, mild and sustainable method for the functionalization of pyridines and their analogues is reported. A zinc-based Lewis acid is used to activate pyridine and its analogues towards nucleophilic aromatic substitution, conjugate addition, and cyclization reactions by binding to the nitrogen on the pyridine ring and activating the pyridine ring core towards further functionalization.

Inhibitors of SARS-3CLpro: virtual screening, biological evaluation, and molecular dynamics simulation studies

SARS-CoV from the coronaviridae family has been identified as the etiological agent of Severe Acute Respiratory Syndrome (SARS), a highly contagious upper respiratory disease that reached epidemic status in 2002. SARS-3CL(pro), a cysteine protease indispensible to the viral life cycle, has been identified as one of the key therapeutic targets against SARS. A combined ligand and structure-based virtual screening was carried out against the Asinex Platinum collection. Multiple low micromolar inhibitors of the enzyme were identified through this search, one of which also showed activity against SARS-CoV in a whole cell CPE assay. Furthermore, multinanosecond explicit solvent simulations were carried out using the docking poses of the identified hits to study the overall stability of the binding site interactions as well as identify important changes in the interaction profile that were not apparent from the docking study. Cumulative analysis of the evaluated compounds and the simulation studies led to the identification of certain protein-ligand interaction patterns which would be useful in further structure based design efforts.

Antagonists of the human A(2A) adenosine receptor. 4. Design, synthesis, and preclinical evaluation of 7-aryltriazolo[4,5-d]pyrimidines

Antagonism of the human A(2A) receptor has been implicated as a point of therapeutic intervention in the alleviation of the symptoms associated with Parkinson's disease. This is thought to occur, at least in part, by increasing the sensitivity of the dopaminergic neurons to the residual, depleted levels of striatal dopamine. We herein describe a novel series of functionalized triazolo[4,5-d]pyrimidine derivatives that display functional antagonism of the A(2A) receptor. Optimization of these compounds has resulted in improvements in potency, selectivity, and the pharmacokinetic properties of key derivatives. These efforts have led to the discovery of 60 (V2006/BIIB014), which demonstrates strong oral activity in commonly used models of Parkinson's disease. Furthermore, this derivative has shown excellent preclinical pharmacokinetics and has successfully completed phase I clinical studies. This compound is presently undergoing further clinical evaluation in collaboration with Biogen Idec.

2-Amino-6-furan-2-yl-4-substituted nicotinonitriles as A2A adenosine receptor antagonists

A 2A adenosine receptor antagonists usually have bi- or tricyclic N aromatic systems with varying substitution patterns to achieve desired receptor affinity and selectivity. Using a pharmacophore model designed by overlap of nonxanthine type of previously known A 2A antagonists, we synthesized a new class of compounds having a 2-amino nicotinonitrile core moiety. From our data, we conclude that the presence of at least one furan group rather than phenyl is beneficial for high affinity on the A 2A adenosine receptor. Compounds 39 (LUF6050) and 44 (LUF6080) of the series had K i values of 1.4 and 1.0 nM, respectively, with reasonable selectivity toward the other adenosine receptor subtypes, A 1, A 2B, and A 3. The high affinity of 44 was corroborated in a cAMP second messenger assay, yielding subnanomolar potency for this compound.

Antagonists of the human adenosine A2A receptor. Part 3: Design and synthesis of pyrazolo[3,4-d]pyrimidines, pyrrolo[2,3-d]pyrimidines and 6-arylpurines

A series of pyrazolo[3,4-d]pyrimidine, pyrrolo[2,3-d]pyrimidine and 6-arylpurine adenosine A(2A) antagonists is described. Many examples were highly selective against the human A(1) receptor sub-type and were active in an in vivo model of Parkinson's disease.