Identification, Synthesis, and Control of Process-Related Impurities in the Antipsychotic Drug Substance Brexpiprazole

This article describes the identification, synthesis, and control of several unknown related substances present in the form of critical impurities that were observed during the process development for the antipsychotic drug substance brexpiprazole (BRX). On the basis of liquid chromatography-mass spectrometry (LC-MS) evidence of impurities and analysis of the employed synthetic route of BRX, the structures of the unknown impurities were proposed. Many critical impurities were synthesized, and their chemical structures were established using different spectroscopy techniques. To the best of our knowledge, this is the first report where several new impurities were recognized, addressed, and controlled effectively during the development of a robust and efficient process for the BRX drug substance.