Novel small molecule antagonists of NPBWR1 (GPR7) are herein reported. A high- throughput screening (HTS) of the Molecular Libraries-Small Molecule Repository library identified 5-chloro-4-(4-methoxyphenoxy)-2-(p-tolyl) pyridazin-3 (2H)-one as a NPBWR1 hit antagonist with micromolar activity. Design, synthesis and structure–activity relationships study of the HTS-derived hit led to the identification of 5-chloro-2-(3, 5-dimethylphenyl)-4-( ...