Stability of unused reconstituted bortezomib in original manufacturer vials

Background. Bortezomib is a modified dipeptidyl boronic acid analogue used to treat multiple myeloma, mantle cell lymphoma, and, more recently, renal transplantation graft rejection. As per manufacturer recommendations, bortezomib is to be administered within 8h of preparation or may be stored for up to 8h in the vial or a syringe following reconstitution. Preserving unused reconstituted bortezomib beyond these 8h may allow for cost savings. This study aims to examine the stability of unused reconstituted bortezomib when stored at 4°C for up to 15 days.Methods. Using an LC-MS/MS assay, the concentration of reconstituted bortezomib was measured at predetermined time points following storage at 4°C in the manufacturer vial. Percent bortezomib remaining at a time point was calculated versus initial bortezomib concentration.Results. The concentrations of bortezomib were found to be 51.93ng/mL±4.60 after 1 day of storage, 57.40ng/mL±4.77 after 8 days of storage, and 49.43ng/mL±2.85 after 15 days of storage. The percent of bortezomib remaining was 110.53% and 95.19% after 8 days and 15 days, respectively. Conclusion. Unused reconstituted bortezomib is stable for up to 15 days stored at 4°C in the original manufacturer vial. Such use of bortezomib may improve cost efficiency by reducing bortezomib waste.