Intraocular pharmacokinetics and safety of a humanized monoclonal antibody in rabbits after intravitreal administration of a solution or a PLGA microsphere formulation

Abstract

Poly(lactic-co-glycolic) acid (PLGA) bioresorbable microspheres are used for controlled-release drug delivery and are particularly promising for ocular indications. The objective of the current study was to evaluate the pharmacokinetics and safety of a recombinant human monoclonal antibody (rhuMAb HER2) in rabbits after bolus intravitreal administration of a solution or a PLGA-microsphere formulation. On Day 0, forty-eight male New Zealand white rabbits (2.3-2.6 kg) were immobilized with intramuscular ketamine/xylazine, and the test materials were injected directly into the vitreous compartment. Group 1 animals received rhuMAb HER2 in 50:50 lactide: glycolide PLGA microspheres; Group 2 animals received rhuMAb HER2 in solution (n = 24/group). The dose for each eye was 25 microg (50 microl). After dosing, animals were sacrificed at 2 min, and on 1, 2, 4, 7, 14, 23, 29, 37, 44, 50, and 56 days (n = 2/timepoint/group). Safety assessment included direct ophthalmoscopy, clinical observations, body weight, and hematology and clinical chemistry panels. At necropsy, vitreous and plasma were collected for pharmacokinetics and analysis for antibodies to rhuMAb HER2, and the vitreal pellet (Group 1) was prepared for histologic evaluation. All animals completed the study per protocol-both treatments were well tolerated, and no suppurative or mixed inflammatory cell reaction was observed in the vitreal samples (Group 1) at any of the time points examined. Antibodies to rhuMAb HER2 were detected in plasma samples by Day 7 in both treatment groups, but infrequently in vitreous samples. There were no safety implications associated with this immune response. The in vitro characterization of the PLGA microspheres provided reasonable projections of the in vivo rhuMAb HER2 release kinetics (Group 1). The total amount of antibody that was released was similar in vitro (25.9%) and in vivo (32.4%). RhuMAb HER2 (Group 2) was cleared slowly from the vitreous compartment, with initial and terminal half-lives of 0.9 and 5.6 days, respectively. The volume of distribution approximated the vitreous volume in a rabbit eye.

Levels of vascular endothelial growth factor and pigment epithelium-derived factor in eyes before and after intravitreal injection of bevacizumab

“…Thus, bevacizumab reduces free VEGF and inhibits its activity. Although experimental data on primates suggested that the full-length antibody might not penetrate the internal limiting membrane of the retina, 25 recent studies have shown that the full-length antibody does penetrate into the rabbit 26 …”

Injectable Chemically Crosslinked Hydrogel for the Controlled Release of Bevacizumab in Vitreous: A 6-Month In Vivo Study

“…Other published studies on bevacizumab controlled release formulations showed less significant improvement (e.g., five times higher than bolus injection). 22,30 According to the IC50 of bevacizumab in vitro 31 and the concentration of VEGF in disease state in human eye, 32 the therapeutically relevant concentration should be in the order of 50 ng/mL. The formulation we tested was able to maintain the concentration above this level for at least 6 months.…”

Protein Transport to Choroid and Retina following Periocular Injection: Theoretical and Experimental Study

“…7. For an assumed GFP clearance rate from the vitreous of 10 )4 s )1 (less than the aqueous turnover rate 12 , but significantly faster than the clearance rate for monoclonal antibodies 23,24 ), the peak interstitial concentration in the retina is 0.75 lM (Fig. 7a), less than half that achieved by periocular injection (Fig.…”