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Leslie J. Dickmann, Victor Yip, Cuiwen Li, Juan Abundes, Mauricio Maia, Cynthia Young, Shannon Stainton, Philip E. Hass, Sean B. Joseph, Saileta Prabhu, C. Andrew Boswell; Evaluation of Fluorophotometry to Assess the Vitreal Pharmacokinetics of Protein Therapeutics. Invest. Ophthalmol. Vis. Sci. 2015;56(11):6991-6999. doi: https://doi.org/10.1167/iovs.15-17457.
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In this work, we assessed the ability of fluorophotometry to measure the vitreal pharmacokinetics (PK) of fluorescently-labeled ranibizumab in the rabbit after intravitreal injection. We compared these values to those obtained using enzyme-linked immunosorbent assays (ELISA). Data obtained in this study were also compared to historical ranibizumab ocular PK data, either measured in-house or previously published.
Three individual in vivo studies were performed in New Zealand White rabbits to assess the feasibility of using fluorophotometry to measure rabbit ocular PK of ranibizumab; explore the dynamic range of dosing fluorescently-labeled ranibizumab; and directly compare ranibizumab concentrations and calculated PK parameters measured by vitreal fluorophotometry to those measured using ELISA.
In direct comparisons between fluorophotometry and ELISA, the calculated clearance (CL) values were 0.26 and 0.21 mL/day, the volumes of distribution at steady state (Vss) were 0.80 and 0.94 mL, the half-lives (t1/2) were 3.1 and 2.9 days and the dose normalized areas under the curve (AUC/D) were 4.7 and 3.9 μg·day/mL/μg, respectively. These values fell within the ranges of 0.13 to 0.44 mL/day for CL, 0.5 to 1.8 mL for Vss, 2.8 to 3.5 days for t1/2, and 2.3 to 7.9 μg·day/mL/μg for AUC/D that have been either measured previously in-house or published elsewhere.
Although not suitable for measuring retinal concentrations, fluorophotometry is a valuable, noninvasive method to measure vitreous concentrations of protein therapeutics after intravitreal injection.
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