A multi-technique approach using LC–NMR, LC–MS, semi-preparative HPLC, HR–NMR and HR–MS for the isolation and characterization of low-level unknown impurities in GW876008, a novel corticotropin-release factor 1 antagonist

A multi-technique approach was applied in order to fully characterize four low-level unknown impurities of GW876008, a novel CRF1 receptor antagonist. Liquid chromatography (LC)–NMR spectroscopy was used in combination with LC–MS to obtain detailed information regarding the structure of the two major impurities present in batches of GW876008 and observed in the first synthetic scale-up for preclinical use. Two additional impurities were unexpectedly found at greater levels in a large scale synthesis for clinical use and their structure was elucidated by means of high resolution (HR)–MS and HR–NMR, after a small scale preparative HPLC purification step. This structural information was useful in terms of shedding light on the typical impurity profile of this new chemical entity with the aim to support the early development package for Phase I clinical studies.