LC-MS/MS characterization of pirtobrutinib impurities and product degradation: stability studies

Abstract

This study examined the fragmentation, degradation pathways and DPs of pirtobrutinib, which have not been previously reported in the literature. The main goal of the current work is to develop, validate, and characterize forced degradation products using LC-MS/MS. An isocratic HPLC methodology was developed for the quantitative measurement of pirtobrutinib at a λ_max of 219 nm. The procedure used was straightforward, well defined, proven, and selective. The samples were subjected to isocratic elution using an Agilent Eclipse C18 column (150 × 4.6 mm, 3.5 μ). The mobile phase was supplied at a flow rate of 1.0 mL per minute in a 30 : 70 v/v ratio, containing 0.1% formic acid and acetonitrile. A linear response was observed within the 0.0–150 μg mL⁻¹ concentration range. It was found that the limits of quantitation and detection for pirtobrutinib were 0.1 and 0.3, respectively. The method was assessed for system suitability, linearity, precision, accuracy, and robustness in accordance with standard ICH guidelines. It was found that the results were within acceptable limits. A variety of stress conditions, such as acids, alkalis, hydrolysis, oxidation, reduction as well as photo- and thermal degradations, were applied to the drug to test the method's efficiency and stability. Acidic, alkaline, peroxide, and reduction conditions showed significant degradation. Degradation products produced during the forced degradation studies were analyzed and characterized using mass spectrometry (MS/MS). Thus, the proposed method can also be used for the quantitation of pirtobrutinib in the presence of its degradation products.