Analytical method development, identification, and characterization of stress degradation products of idelalisib by ultrahigh‐performance liquid chromatography with photodiode array and ultrahigh‐performance liquid chromatography with electrospray ionization quadrupole time‐of‐flight mass spectrometry studies

Rationale As per International Council for Harmonization (ICH) drug stability test guideline Q1A(R2), inherent stability characteristics of a drug should be studied. This work was designed to investigate inherent degradation characteristics of the drug idelalisib under ICH prescribed stress conditions, identify its degradation products, and postulate their corresponding degradation pathways. Methods Idelalisib was subjected to the ICH prescribed conditions of hydrolytic (neutral, acidic, and alkaline), photolytic, oxidative, and thermal stress according to ICH guideline Q1A(R2). An ultrahigh‐performance liquid chromatography with photodiode array (UHPLC‐PDA) method was developed to adequately resolve the drug from its degradation products, validated as per the ICH guidelines, and subsequently extended to UHPLC with electrospray ionization quadrupole time‐of‐flight mass spectrometry (ESI‐QTOFMS) studies to identify the degradation products. Results Significant degradation was noted under conditions of acidic/alkaline hydrolysis, acid photolysis, and oxidative stress. The UHPLC/ESI‐QTOFMS studies revealed the generation of four degradation products (I–IV), which were satisfactorily resolved from the drug by UHPLC on a Kinetex® C18 (100 × 4.6 mm; 2.6 μm) column by the developed isocratic elution method. Detection wavelength was selected as 270 nm. All the degradation products (I–IV) could be identified and characterized from their mass spectral data. The degradation pathways for the generation of various products from the drug were postulated. Conclusions A UHPLC‐PDA method was developed and validated for idelalisib. Four degradation products of idelalisib were revealed through UHPLC/ESI‐QTOFMS studies, and corresponding degradation pathways were postulated for the same.