Discovery of Novel and Selective Adenosine A2A Receptor Antagonists for Treating Parkinson's Disease through Comparative Structure-Based Virtual Screening.

Among non-dopaminergic strategies for combating Parkinson's disease (PD), antagonism of the A2A adenosine receptor (AR) has emerged to show great potential. In this study, on the basis of two crystal structures of the A2A AR with the best capability to distinguish known antagonists from decoys, docking-based virtual screening (VS) was conducted to identify novel A2A AR antagonists. A total of 63 structurally diverse compounds identified by VS were submitted to experimental testing, and 11 of them exhibited substantial activity against the A2A AR (Ki < 10 µM), including two compounds with Ki below 1 µM (compound 43, 0.42 µM; compound 51, 0.27 µM) and good A2A/A1 selectivity (fold < 0.1). Compounds 43 and 51 demonstrated antagonistic activity according to the results of cAMP measurements (cAMP IC50 = 1.67 and 1.80 µM, respectively) and showed good efficacy in the haloperidol-induced catalepsy (HIC) rat model for PD at doses of up to 30 mg/kg. Further lead optimization based on a substructure searching strategy led to the discovery of compound 84 as an excellent A2A AR antagonist (A2A Ki = 54 nM, A2A/A1 fold < 0.1, cAMP IC50 = 0.3 µM) that exhibited significant improvement in anti-PD efficacy in the HIC rat model.

Identification of a New Series of Potent Adenosine A2A Receptor Antagonists Based on 4-Amino-5-carbonitrile Pyrimidine Template for the Treatment of Parkinson's Disease.

Adenosine receptor A2A antagonists have emerged as potential treatment for Parkinson's disease in the past decade. We have recently reported a series of adenosine receptor antagonists using heterocycles as bioisosteres for a potentially unstable acetamide. These compounds, while showing excellent potency and ligand efficiency, suffered from moderate cytochrome P450 inhibition and high clearance. Here we report a new series of adenosine receptor A2A antagonists based on a 4-amino-5-carbonitrile pyrimidine template. Compounds from this new template exhibit excellent potency and ligand efficiency with low cytochrome P450 inhibition. Although the clearance remains moderate to high, the leading compound, when dosed orally as low as 3 mg/kg, demonstrated excellent efficacy in the haloperidol induced catalepsy rat model for Parkinson's disease.