SIX-MONTH STABILITY OF BEVACIZUMAB (AVASTIN) BINDING TO VASCULAR ENDOTHELIAL GROWTH FACTOR AFTER WITHDRAWAL INTO A SYRINGE AND REFRIGERATION OR FREEZING SOPHIE J. BAKRI, MD,* MELISSA R. SNYDER, PHD,† JOSE S. PULIDO, MD, MS, MPH,* COLIN A. MCCANNEL, MD,* WILLIAM T. WEISS, RPH,‡ RAVINDER J. SINGH, PHD† Purpose: To determine the change in anti–vascular endothelial growth factor (VEGF) activity of bevacizumab (Avastin, Genentech, Inc., San Francisco, CA) after refrigeration or freezing. Methods: Samples of bevacizumab were drawn up from new vials into plastic tuberculin syringes and refrigerated at 4°C for 1 week, 3 weeks, 1 month, 3 months, and 6 months. The vials and syringes were stored at 4°C, and the syringes were capped with a needle. One syringe was frozen at -10°C. The bevacizumab concentration was measured, via its binding to VEGF-165. Results: The percentage of degradation of bevacizumab in the previously pierced vials stored at 4°C compared with that in the unpierced vial was 9.6% at 3 months and 12.7% at 6 months. The bevacizumab drawn into the syringe and stored at 4°C was degraded by 1.6% at 1 week, 0% at 3 weeks, 8.8% at 3 months, and 15.9% at 6 months. The bevacizumab frozen in a syringe at -10°C was degraded by 12.0% at 6 months. Conclusion: The anti-VEGF activity of bevacizumab may degrade minimally over time, with storage. RETINA 26:519 –522, 2006 B evacizumab (Avastin, Genentech, Inc., San Fran- cisco, CA) is a recombinant humanized monoclo- nal IgG1 antibody that inhibits human vascular endo- thelial growth factor (VEGF). The drug is approved by the US Food and Drug Administration for intrave- nous use in combination with 5-fluorouracil– based chemotherapy for metastatic colorectal cancer. It has been administered intravitreally in VEGF-mediated diseases, such as choroidal neovascularization, 1,2 cen- tral retinal vein occlusion, 3 proliferative diabetic reti- nopathy, 4 and other retinal diseases. Bevacizumab is a clear to slightly opalescent, col- orless to pale brown solution with a pH of 6.2. It is supplied in 100-mg and 400-mg preservative-free, sin- From the *Department of Ophthalmology, †Division of Clinical Biochemistry and Immunology, Department of Laboratory Medi- cine and Pathology, and ‡Pharmacy Services, Mayo Clinic, Roch- ester, Minnesota. None of the authors have any proprietary interest in any of the products mentioned in this article. Reprint requests: Sophie J. Bakri, MD, or Ravinder J. Singh, PhD, Mayo Clinic, 200 First Street SW, Rochester, MN 55905; e-mail: singh.ravinder@mayo.edu; bakri.sophie@mayo.edu 519