Stability of Generic Formulations of Bortezomib 1.0 and 2.5 mg/mL in Vials and Syringes Stored at 4°C and Room Temperature (23°C or 25°C).

Background: The availability of generic versions of bortezomib raises questions about the reliability of extrapolating stability data from one brand to another.

Objective: To evaluate the stability of bortezomib formulations available from Janssen, Teva Canada, Actavis Pharma, Dr. Reddy's Laboratories, Apotex, and MDA, reconstituted with 0.9% sodium chloride (normal saline) to produce solutions of either 1.0 or 2.5 mg/mL and stored over at least 21 days under refrigeration (4°C) or at room temperature (either 23°C or 25°C) in the manufacturer's original glass vials or in polypropylene syringes.

Methods: On study day 0, solutions with concentration 1.0 mg/mL or 2.5 mg/mL of the Teva, Actavis, Dr. Reddy's, Apotex, and MDA generic formulations were prepared. Three units of each type of container (glass vials and syringes) were stored at 4°C and 3 units at room temperature. Concentration and physical inspection were completed on at least 8 study days (including day 0) over a 21- to 84-day study period. Bortezomib concentrations were determined by a validated stability-indicating liquid chromatographic method with ultraviolet detection. The end point of these studies was the time to reach 90% of the initial concentration (T-90) with 95% confidence, which is expressed as "T-90", where CI refers to the confidence interval. In addition to estimating the T-90, differences in stability among products from all manufacturers were compared using multiple linear regression. Previously published data for the Janssen product were included in the overall comparisons.

Results: In all of the studies, the analytical method separated degradation products from bortezomib, such that the concentration of bortezomib was measured specifically, accurately (deviations < 2.5%), and reproducibly (average replicate error 2.5%). During all studies, solutions retained more than 94% of the initial concentration at 4°C. The T-90 exceeded the study period for all formulations under all combinations of concentration, container, and temperature, except the 84-day study for the MDA product. Multiple linear regression showed no significant differences among manufacturers ( = 0.57).

Conclusions: In this study, formulations of bortezomib currently marketed in Canada (by Janssen, Teva Canada, Actavis Pharma, Dr. Reddy's Laboratories, Apotex, and MDA) were pharmaceutically equivalent and interchangeable. Given that there was no difference in stability related to manufacturer, nominal concentration, or container, we conclude that these formulations are physically and chemically stable for at least 35 days under refrigeration and at least 25 days at room temperature.