Background Bevacizumab (BVZ), the active substance of Avastin (25 mg/mL BVZ), is a humanised anti-vascular endothelial growth factor (VEGF) monoclonal antibody indicated in the treatment of several cancers.

Purpose To evaluate the biological activity (BA) that remains in the medicine Avastin after opening single-use vials in a long-term study.

Material and methods An indirect non-competitive ELISA was developed for this and validated to test the stability of BA of BVZ. Cross-reaction with other monoclonal antibodies was tested. ELISA plates were sensitised with recombinant VEGF. Calibration function was between 0.01 and 25.0 µg/mL; detection and quantification limits were 0.10 and 0.35 µg/mL; precision – as intraday and interday reproducibility (%RSD) – was <10% and accuracy (% of recovery) >95%. Stress study included mild basic, acidic, oxidative and ionic-strength conditions; temperature 50 and 70°C and light exposure. Surplus samples of Avastin from the daily use of the Hospital Pharmacy Unit were stored at 4°C and -20°C in the dark. The BA was tested up to 57 days.

Results The BA of Avastin was higher than 98% at day 1, and higher than 95% at day 2, but decreased by 15% of the initial BA at day 3. This value was maintained throughout the study (57 days) for the two storage conditions tested. Residual BA remained in all samples submitted to the stress except in samples heated at 70°C. There were no cross reactions with similar IgG1.

Conclusion Regarding BA, the stability of Avastin in the conditions used both refrigerated (4°C) and frozen (-20°C) was maintained for two days. Considering the limit of ±10% used in practical stability studies, it cannot be considered stable from day 3 since the loss of BA was 15%. These results will be further investigated by flow cytometry.

References and/or acknowledgements

1. Financial support: PI10/00201 (MICINN, Government of Spain).

References and/or acknowledgementsNo conflict of interest.