Lamminsalo M, Karvinen T, Subrizi A, Urtti A, Ranta VP. Extended Pharmacokinetic Model of the Intravitreal Injections of Macromolecules in Rabbits. Part 2: Parameter Estimation Based on Concentration Dynamics in the Vitreous, Retina, and Aqueous Humor.
Pharm Res 2020;
37:226. [PMID:
33094404 PMCID:
PMC7581578 DOI:
10.1007/s11095-020-02946-1]
[Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Accepted: 10/05/2020] [Indexed: 01/09/2023]
Abstract
PURPOSE
To estimate the diffusion coefficients of an IgG antibody (150 kDa) and its antigen-binding fragment (Fab; 50 kDa) in the neural retina (Dret) and the combined retinal pigment epithelium-choroid (DRPE-cho) with a 3-dimensional (3D) ocular pharmacokinetic (PK) model of the rabbit eye.
METHODS
Vitreous, retina, and aqueous humor concentrations of IgG and Fab after intravitreal injection in rabbits were taken from Gadkar et al. (2015). A least-squares method was used to estimate Dret and DRPE-cho with the 3D finite element model where mass transport was defined with diffusion and convection. Different intraocular pressures (IOP), initial distribution volumes (Vinit), and neural retina/vitreous partition coefficients (Kret/vit) were tested. Sensitivity analysis was performed for the final model.
RESULTS
With the final IgG model (IOP 10.1 Torr, Vinit 400 μl, Kret/vit 0.5), the estimated Dret and DRPE-cho were 36.8 × 10-9 cm2s-1 and 4.11 × 10-9 cm2s-1, respectively, and 76% of the dose was eliminated via the anterior chamber. Modeling of Fab revealed that a physiological model parameter "aqueous humor formation rate" sets constraints that need to be considered in the parameter estimation.
CONCLUSIONS
This study extends the use of 3D ocular PK models for parameter estimation using simultaneously macromolecule concentrations in three ocular tissues.
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