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Sylvie Julien, Ulrich Schraermeyer; Comparison of intravitreally injected ranibizumab versus aflibercept in the retina and choroid of the primate eye. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4113.
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There is evidence that the Fc domain of anti-VEGF drugs may play a role on their action in the retina and choroid. To establish whether Fc presence affects their distribution in these structures, we used immunohistochemistry to investigate the distribution of aflibercept (with Fc) and ranibizumab (no Fc) in intravitreally injected monkey eyes.
We injected ranibizumab (Lucentis® 0.5mg) or aflibercept (Eylea® 2mg) in the vitreous of eight cynomolgus monkeys, using as controls three untreated animals and one injected with aflibercept's vehicle alone. We studied the distribution of ranibizumab and aflibercept in the retina and choroid, using respectively anti-F(ab) or anti-Fc-fragment antibodies. We further used other antibodies to detect immunoreactivity as follows: glial fibrillary acidic protein (GFAP) for astrocytes and activated Mueller cells; vimentin for Mueller cells; ionized calcium binding adaptor molecule 1(Iba1) for macrophages/microglia; hypoxia-inducible factor (HIF) as a marker for hypoxia.
The distribution of both drugs within the retina and choroid tissue was visualized by their immunoreactivity. Ranibizumab permeated the retina via intercellular clefts (Fig. 1a), whereas aflibercept was taken up already 24 h post-injection by ganglion cells (RGC), cells of the inner and outer retinal layers and retinal pigment epithelium (RPE) (Fig. 1b), leading to individual RPE cell death. Local accumulation and complex formation of both drugs in individual choroidal vessels and choriocapillaris were observed but seemed to be more pronounced after aflibercept treatment. Mueller cells, astrocytes and microglia cells were locally activated after treatment with either drug as well as vehicle alone. HIF was not expressed in retinal cells.
Ranibizumab permeated the retina through intercellular spaces, whereas aflibercept was taken up by neuroretinal cells and RPE, inducing more protein complex formation and individual RPE cell death. The clinical significance and relation of these findings to the Fc domain or to other characteristics of the molecule, remain to be investigated.
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