Forced Degradation Studies to Assess the Stability of a Janus Kinase Inhibitor Using RPLC Method

In optimization studies, it is important to study the retention behavior of the compounds containing the ionizable functional groups under the intended chromatographic conditions. In this study, the influence of pH and acetonitrile (ACN) composition in the mobile phase on chromatographic behavior of tofacitinib (TOF), a Janus kinase (JAK) inhibitor, was investigated in details. First, the chromatographic conditions were optimized using retention factors and pKa values. Then, the developed method was used for the stability studies under various stress conditions, and for the estimation of TOF concentration in tablets. Finally, the method was validated using the International Conference on Harmonization (Q2) guidelines and it was successfully used to separate the TOF degradation products. A linearity range, limit of detection and limit of quantification were determined as 2.0-12.0, 0.416, and 1.260 μg/mL, respectively. Between-day and within-day precisions were found to be as 0.290 and 0.462 for 4 μg/mL, respectively. The result indicates that the developed method is rather effective to separate the parent drug from the degradation products.