Understanding the Stress Testing Characteristics of Apixaban, Structural Elucidation of a Novel Degradation Impurity, and Stability-Indicating Method Development for Quantification of Related Substances

BACKGROUND: People who have non-valvular atrial fibrillation may benefit from taking a new oral anticoagulant called apixaban, which has recently been given the green light by the U.S. Food and Drug Administration. During stress testing, apixaban was found to have a high degree of degradability when subjected to both acidic and basic conditions, and one significant unknown impurity was observed in addition to the major known impurities. OBJECTIVE: Our aim is the isolation and characterization of degradation product observed in stress/forced degradation studies, and also the development of a single HPLC method that is both reliable and accurate for quantifying all 10 related impurities of apixaban. METHODS: Preparative HPLC was used to isolate the degradation product, and 1H NMR, 13C NMR, and MS were used to elucidate the structure of the product. Additionally, a single reverse-phase (RP) HPLC method was developed for quantification of all related impurities of apixaban. RESULTS: Based on the spectral characterization data, the identified unknown degradation impurity was found to be a pH-independent hydrolysis degradation impurity of apixaban. The developed method is specific, linear, accurate, robust, and rugged. CONCLUSION: The isolated and characterized impurities were the same as those found during stress testing. The developed method has been validated for its intended purpose in accordance with the regulatory requirements that were outlined. HIGHLIGHTS: The unknown impurity is a new apixaban degradation impurity that helps us understand its toxicity. The scientific community will benefit from the developed analytical method information as it relates to understanding drug product impurity profiling.