Development and Validation of Highly Sensitive LC–ESI-MS/MS Method for Bortezomib and Its Applications for Plasma Levels and Drug Content of Branded and Generic Formulations in India

In the present study, a highly sensitive and reproducible bio-analytical method was developed using LC–ESI-MS/MS to assess the lower plasma levels of bortezomib in multiple myeloma patients. The gradient elution was optimized using reverse-phase C18 column with mobile phases consisting of water and acetonitrile in 0.1% formic acid. Multiple reaction monitoring mode was used for quantification using precursor-to-product ion transition for bortezomib and sulfadiamethoxine was used as internal standard. This method was validated with a linearity range of 0.195–25 ng mL −1 . Intra-day and inter-day accuracy was 99.17–101.89% and 95.01–102.92% with precision of < 9.87% and < 8.77%, respectively. Bortezomib was stable in plasma samples stored at − 80 °C for up to 10 months. The lower limit of quantification was found to be 0.195 ng mL −1 . This method was also found to be capable of quantifying bortezomib trough levels (ranging 0.19–0.7 ng mL −1 ) in plasma of multiple myeloma patients post-cycle 1–6. Bortezomib content in the commonly prescribed generic formulations was also studied. The concentration in all formulations was within the 90–110% of the innovator, as prescribed by the USFDA, ruling out their role blood level variation. The study supports the use of this method for trough level estimation and therapeutic drug monitoring of bortezomib in multiple myeloma patients.