LC-MS/MS studies for identification and characterization of new forced degradation products of dabrafenib and establishment of their degradation pathway

Dabrafenib (Tafinlar) is used for the treatment of patients with BRAF V600 mutation positive unresectable or metastatic melanoma. Forced degradation study of the drug product and drug substance is very much important in drug development and drug discovery to establish the intrinsic stability and understand its behaviors towards different stress conditions. In the current study, compressive stress testing of dabrafenib has been performed as per the recommendation of ICH guidelines to identify and characterize all major degradation products of dabrafenib (DPD) formed. Drug substances were exposed to different stressed conditions as per ICH recommendations. The present study observed that the dabrafenib drug substance is very much sensitive when exposed to oxidative degradation conditions at 80 °C temperature conditions and also sensitive to photolytic degradation conditions. Dabrafenib is stable when treated in acidic, alkaline, neutral and thermal degradation environments as there is no degradation observed in signification percentage under these stressed conditions. The best separation of eight degradation products and dabrafenib drug substance was obtained in Waters BEH (Ethylene Bridge Hybrid) C-18 column (1.7 µm, 100 mm × 2.1 mm) having mobile phase composed of Formic acid (0.1%) and methanol as Eluent A and Eluent B respectively using 225 nm wavelengths. The volume of injection (5 µL) and flow rate (0.3 mL/min) was set throughout the study. Dabrafenib is highly unstable to oxidative stressed conditions as five major degradation products (DPD-II, DPD-III, DPD-IV, DPD-V and DPD-VII) were obtained when exposed to hydrogen peroxide. When dabrafenib is treated under photolytic degradation conditions, three major DPs were formed (DPD-I, DPD-VI and DP-VIII). These DPs were further identified and characterized on sophisticated HRMS/MS/TOF technique for accurate mass measurement. Characterization of all the degradation products was carried out in the ESI positive mode of ionization. The establishment of the degradation pathway of drug substance and fragmentation pathway of DPs were explained in the present study which was never reported in any literature.