title: Evaluation of Fluorophotometry to Assess the Vitreal Pharmacokinetics of Protein Therapeutics.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  Although not suitable for measuring retinal concentrations, fluorophotometry is a valuable, noninvasive method to measure vitreous concentrations of protein therapeutics after intravitreal injection.
authors.affiliation: Department of Preclinical and Translational Pharmacokinetics Genentech, Inc., South San Francisco, California, United States.
authors.forename: Leslie J
authors.initials: LJ
authors.lastname: Dickmann
authors.affiliation: Department of Preclinical and Translational Pharmacokinetics Genentech, Inc., South San Francisco, California, United States.
authors.forename: Victor
authors.initials: V
authors.lastname: Yip
authors.affiliation: Department of Preclinical and Translational Pharmacokinetics Genentech, Inc., South San Francisco, California, United States.
authors.forename: Cuiwen
authors.initials: C
authors.lastname: Li
authors.affiliation: Department of Bioanalytical Sciences, Genentech, Inc., South San Francisco, California, United States.
authors.forename: Juan
authors.initials: J
authors.lastname: Abundes
authors.affiliation: Department of Bioanalytical Sciences, Genentech, Inc., South San Francisco, California, United States.
authors.forename: Mauricio
authors.initials: M
authors.lastname: Maia
authors.affiliation: Department of In Vivo Studies, Genentech, Inc., South San Francisco, California, United States.
authors.forename: Cynthia
authors.initials: C
authors.lastname: Young
authors.affiliation: Department of In Vivo Studies, Genentech, Inc., South San Francisco, California, United States.
authors.forename: Shannon
authors.initials: S
authors.lastname: Stainton
authors.affiliation: Department of Protein Chemistry, Genentech, Inc., South San Francisco, California, United States.
authors.forename: Philip E
authors.initials: PE
authors.lastname: Hass
authors.affiliation: Department of Preclinical and Translational Pharmacokinetics Genentech, Inc., South San Francisco, California, United States.
authors.forename: Sean B
authors.initials: SB
authors.lastname: Joseph
authors.affiliation: Department of Preclinical and Translational Pharmacokinetics Genentech, Inc., South San Francisco, California, United States.
authors.forename: Saileta
authors.initials: S
authors.lastname: Prabhu
authors.affiliation: Department of Preclinical and Translational Pharmacokinetics Genentech, Inc., South San Francisco, California, United States.
authors.forename: C Andrew
authors.initials: CA
authors.lastname: Boswell
mesh_terms: D000818:Animals; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005455:Fluorescent Antibody Technique; D015590:Fluorophotometry; D006207:Half-Life; D007155:Immunologic Factors / Q000008:administration & dosage / Q000032:analysis / Q000493:pharmacokinetics*; D058449:Intravitreal Injections; D008297:Male; D011817:Rabbits; D000069579:Ranibizumab / Q000008:administration & dosage / Q000032:analysis / Q000493:pharmacokinetics*; D014822:Vitreous Body / Q000737:chemistry / Q000378:metabolism*
chemical_list: D007155:Immunologic Factors; D000069579:Ranibizumab