In this study, we report the identification of potent pyrimidoindazoles as phosphodiesterase10A (PDE10A) inhibitors by using the method of fragment-based drug discovery (FBDD). The pyrazolopyridine derivative 2 was found to be a fragment hit compound which could occupy a part of the binding site of PDE10A enzyme by using the method of the X-ray co-crystal structure analysis. On the basis of the crystal
Provided is a compound having a PDE10A inhibitory action, and useful as a medicament for the prophylaxis or treatment of mental diseases such as schizophrenia and the like, and the like. A compound represented by the formula (I):
wherein each symbol is as defined in the DESCRIPTION, or a salt thereof.