Pharmacokinetics and Retinal Distribution of Ranibizumab, a Humanized Antibody Fragment Directed Against VEGF-A, Following Intravitreal Administration in Rabbits

Purpose: Ranibizumab (Lucentis) is a humanized antigen-binding fragment designed to inhibit all isoforms and active degradation products of vascular endothelial growth factor A (VEGF-A); it is in clinical development for the treatment of neovascular age-related macular degeneration (AMD). This study evaluated its pharmacokinetics (PK) and retinal distribution in rabbits when administered intravitreally (ITV).

Methods: A total of 27 New Zealand white rabbits received a single bilateral ITV injection of ranibizumab 625 muicrog/eye (Group 1, n = 24) or I-labeled ranibizumab 625 microg/eye, 22.5 microCi/eye (Group 2, n = 3). Ranibizumab concentration was determined in the vitreous, aqueous humor, and serum up to 60 days postdose by enzyme-linked immunosorbent assay in Group 1. Group 2 eyes were microautoradiographed on days 1-4.

Results: Ranibizumab has a terminal half-life of 2.9 days in the ocular compartments. Systemic exposure was low, measuring less than 0.01% of vitreous exposure when comparing AUC0-t values. Microautoradiography analysis demonstrated that ranibizumab penetrated all retinal layers, reaching the choriocapillaris on days 1, 2, and 4.

Conclusions: This study demonstrates that following ITV injection, ranibizumab has a vitreous half-life of 2.9 days with minimal systemic exposure. Ranibizumab rapidly penetrates through the retina to reach the choroid, supporting its clinical development for neovascular AMD.