Neuroscience Letters 488 (2011) 1–5 Contents lists available at ScienceDirect Neuroscience Letters journal homepage: www.elsevier.com/locate/neulet Novel 8-(furan-2-yl)-3-benzyl thiazolo [5,4-e][1,2,4] triazolo [1,5-c] pyrimidine-2(3H)-thione as selective adenosine A 2A receptor antagonist Sandeep Kumar Barodia, Chandra Bhushan Mishra, Amresh Prakash, J.B. Senthil Kumar, Namrata Kumari, Pratibha Mehta Luthra ∗ Medicinal Chemistry Division, Dr. B.R. Ambedkar Center for Biomedical Research, University of Delhi, North Campus, Mall Road, Delhi 110007, India article info Article history: Received 2 March 2010 Received in revised form 31 July 2010 Accepted 4 August 2010 Keywords: Adenosine A 2A receptor Antagonist BTTP G-protein coupled receptors cAMP Dopamine abstract Adenosine A 2A receptor (A 2A R) antagonists have emerged as potential drug candidates to alleviate pro- gression and symptoms of Parkinson’s disease (PD), and reduce the dopaminergic side effects. The synthesis of novel compound 8-(furan-2-yl)-3-benzyl thiazolo [5,4-e][1,2,4] triazolo [1,5-c] pyrimidine- 2-(3H)-thione (BTTP) was carried out to evaluate the potential of BTTP as A 2A R antagonist using SCH58261, a standard A 2A R antagonist. The strong interaction of BTTP with A 2A R(G = -12.46 kcal/mol and K i = 0.6 nM) in silico analysis was confirmed by radioligand receptor binding studies showing high affinity (K i = 0.004 nM) and selectivity with A 2A R(A 2A /A 1 = 1155-fold). The effect of CGS21680 (selective A 2A R agonist) induced cAMP concentration (0.1 pmol/ml) in HEK293 cells was antagonized with BTTP (0.065 pmol/ml) and SCH58261 (0.075 pmol/ml). Furthermore, BTTP pre-treated (5, 10 and 20 mg/kg) haloperidol-induced mice demonstrated significant attenuation in catalepsy and akinesia. BTTP induced elevation in the striatal dopamine concentration (2.90 M/mg of tissue) was comparable to SCH58261 (2.92 M/mg of tissue) at the dose of 10 mg/kg. The results firmly articulate that BTTP possesses potential A 2A R antagonist activity and can be further explored for the treatment of PD. © 2010 Elsevier Ireland Ltd. All rights reserved. Adenosine A 2A receptors (A 2A Rs) are highly expressed in striatopal- lidal neurons and have emerged as prime non-dopaminergic target in the search for improved therapeutics for Parkinson’s disease (PD) [21]. Antagonists of the A 2A R have been proved as a leading candi- date class of non-dopaminergic anti-Parkinsonian agents and also reported to exhibit neuroprotective effects [4,6]. Numerous struc- turally diverse A 2A R antagonists such as xanthine compounds based on the structures of naturally occurring methylxanthines, caffeine and theophylline [12,19] and non-xanthine compounds SCH58261 and ZM241385, have been synthesized. Xanthine and non-xanthine compounds possessed strong binding affinity with A 2A R and high selectivity versus A 1 receptor. However, xanthine compounds such as KW6002 were mostly unsuccessful in clinical trials [3] and non- xanthines such as SCH58261 suffered from lower selectivity, poor solubility and poor pharmacokinetic profile [11]. Therefore, we directed our efforts to search for a novel compound superseding the limitations of known A 2A R antagonists. The structure-based drug design utilizes in silico molecular docking as one of the strate- gies to elucidate putative ligand–receptor interactions [2]. Several agonists and antagonists have been docked in the A 2A R model to ∗ Corresponding author. Tel.: +91 11 27666272; fax: +91 11 27666248. E-mail addresses: pmlsci@yahoo.com, pmluthra@acbr.du.ac.in (P.M. Luthra). predict their interaction with the binding site of A 2A R [10]. In our earlier study, in silico binding of naphtha [1,2-d] thiazol-2-amine with A 2A R was reported using recently solved human A 2A R model [9,15]. In vitro characterization of number of non-xanthine adeno- sine receptor antagonists has been described, primarily by binding studies and cAMP functional assay [20]. Antagonist of dopamine D 2 receptors, haloperidol (an anti-psychotic drug) depletes nigrostri- atal dopamine release [7] to produce motor impairment and is used to evaluate potential antiparkinsonian activity in animal models [14]. Blockade of A 2A Rs with SCH58261 alleviated haloperidol- induced Parkinsonian-like muscle rigidity in rodent models of PD [22]. Based on the pyrazolotriazolopyrimidine core of selective A 2A R antagonist SCH58261, novel ligand BTTP was designed to gen- erate selective antagonist for A 2A R. Pyrazolo ring of the tricyclic core of SCH58261 has been replaced by thiazole ring, retaining the structural necessities of non-xanthine tricyclic triazolopyrim- idine derivatives for antagonistic activity as reported earlier [23]. N-ethylphenyl side chain of SCH58261 was substituted by N-benzyl side chain in BTTP (Fig. 1). The interaction of BTTP with selective amino acid residues of human A 2A R active site was studied by molecular docking anal- ysis. In vitro radioligand binding study was carried to evaluate the binding affinity and selectivity of BTTP with A 2A R. To assess the potential A 2A R antagonistic property of BTTP in vitro, cAMP 0304-3940/$ – see front matter © 2010 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.neulet.2010.08.006