LC and LC-MS/MS studies for identification and characterization of new degradation products of ibrutinib and elucidation of their degradation pathway.

Forced degradation/stress degradation studies of ibrutinib drug were done in hydrolytic (acidic, alkaline and neutral), thermal, photolytic and oxidative degradation conditions in different temperature conditions as per International Conference on Harmonization (ICH) guideline Q1A(R2) in order to identify and characterize degradation products (DPs) of ibrutinib. The study revealed that ibrutinib is extremely sensitive to oxidative degradation even at room temperature. The drug substance is highly sensitive to alkaline hydrolysis and susceptible to acidic hydrolysis at 80 °C temperature condition, whereas found stable in neutral, photolytic and thermal stress conditions. Successful separation of ibrutinib and its ten degradation products formed during stress degradation condition were observed using Waters Acquity UPLC C-18 stationary phase (100 mm × 2.1 mm, 1.7 μm) with gradient elution using mobile phase consisting of Eluent-A: ammonium acetate (20 mm, pH-6) and Eluent-B: acetonitrile. The detection was carried out at 215 nm wavelength. Flow rate was set at 0.3 mL/min with injection volume of 5 μL. The drug substance degraded to one degradation product (DP-I) in acidic hydrolysis, five DPs (DP-I, DP-II, DP-V, DP-VIII and DP-IX) in basic hydrolysis and five DPs (DP-III, DP-IV, DP-VI, DP-VII and DP-X) in oxidative degradation condition. A novel and highly sensitive HRMS/MS/TOF method was developed to identify and characterize all the ten DPs formed during stress study. All the DPs were characterized using ESI positive mode. Except DP-I, all the degradation products formed were found to be new degradation impurities and their fragmentation pathways have never been reported earlier. The proposed mechanism and pathway of degradation products of ibrutinib were discussed and outlined.