Vitreous Levels of Unbound Bevacizumab and Unbound Vascular Endothelial Growth Factor in Two Patients

In Brief Background: Vitreous levels of unbound bevacizumab (Avastin) and unbound vascular endothelial growth factor (VEGF) were determined in two patients. Patient 1 underwent repair of an 8-day-old rhegmatogenous retinal detachment 4 weeks after a single intravitreal bevacizumab injection, and Patient 2 underwent vitreous biopsy for endophthalmitis 48 hours after a combined bevacizumab and triamcinolone injection. Methods: The samples of vitreous fluid were analyzed for unbound bevacizumab and unbound VEGF levels using microsphere immunoassays targeted for bevacizumab and VEGF. Results: In Patient 1, the unbound bevacizumab level was 0.16% of the loading dose (or 500,000 pg/mL) and the unbound VEGF concentration was <41 pg/mL 4 weeks after the bevacizumab injection. In Patient 2, the unbound bevacizumab level was 53% of the loading dose (or 166,000,000 pg/mL) at 48 hours, with an unbound VEGF level of <41 pg/mL. Conclusion: A single dose of intravitreal bevacizumab is likely to provide complete intravitreal VEGF blockade for a minimum of 4 weeks, with an intravitreal bevacizumab half-life of ≈3 days. Determination of vitreous levels of unbound vascular endothelial growth factor (VEGF) and unbound bevacizumab in two patients who developed complications after intravitreal bevacizumab injections demonstrated effective intravitreal VEGF blockade for 4 weeks and an intravitreal bevacizumab half-life of ≈3 days.