Development and Validation of a LC‐MS/MS Method for Ripretinib and Its Metabolite: Example of a Journey From Laboratory Bench to Routine Application With a Greenness Assessment

Therapeutic drug monitoring of protein kinase inhibitors is widely practiced worldwide. Based on the example of ripretinib dosage requested by a clinician, we detailed the process of method development, using a literature‐based approach while ensuring the sustainability of the method to be as environmentally friendly as possible. Therefore, a UPLC‐MS/MS method for ripretinib and its active metabolite was optimized and validated using the corresponding stable isotopic internal standards in human plasma. The procedure employed a mobile phase mixture of water with 1% acetic acid and 0.1% formic acid, and acetonitrile. Positive electrospray ionization was performed, coupling with multiple reaction monitoring of m / z 510.4 → 417.4 and 510.4 → 389.4 for ripretinib, and 496.3 → 403.3 and 496.3 → 375.3 for N ‐desmethyl‐ripretinib. The method was successfully validated according to the current version of the ICH Guideline provided by the EMA. The greenness assessment score of this procedure was better than previously published approaches using the AGREE metric. The validated UPLC‐MS/MS method successfully monitored ripretinib and its metabolite concentrations in clinical and preclinical models.