Purpose:
To investigate a fluorescent molecular probe linked to a humanized monoclonal antibody against vascular endothelial growth factor (VEGF) for in vivo imaging of VEGF within the retina.
Methods:
Bevacizumab was covalently attached to a near-infrared indocyanine dye yielding a soluble conjugate. Its binding properties were assessed by an in vitro proliferation assay. Retinal laser lesions were placed around the optic nerve head in Dark Agouti rats. The dye conjugate was intraperitoneally, intravenously or intravitreally injected. Its uptake was recorded in vivo using confocal scanning laser ophthalmoscopy (cSLO) at pre-defined time intervals for up to 60 days
Results:
No significant difference of cellular activity could be found between the conjugated and the unconjugated antibody in the proliferation assay in vitro (71%, 75% respectively; control=100%). Following intraperitoneal injection, no fluorescence was visible on the same day, while one day later a strong signal became present in the retinal vasculature and within roundish laser lesions. Furthermore, multiple hyperfluorescent spots were visible. By contrast, strong fluorescence became visible immediately after intravenous and intravitreal injection. With all three different modes of application, signal intensity continuously decreased after injection. Few fluorescent spots were still visible on day 60.
Conclusions:
Pharmacokinetics of fluorescent-labeled bevacizumab can be investigated in vivo following intraperitoneal, intravenous and intravitreal injection. Following extensive investigations, the ability of monitoring VEGF spatially and temporally in vivo may be applicable in patients for earlier diagnosis and more refined individualized anti-VEGF therapies with the aim of optimizing functional outcomes.
Keywords: vascular endothelial growth factor • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • retinal neovascularization