Abstract
Purpose: :
To evaluate the comparative efficacy of prophylactic and therapeutic treatment modalities using a potent, selective, orally bioavailable small molecule CCR2 antagonist in a model of age-related macular degeneration.
Methods: :
On day 1 of the study, four laser lesions were introduced into the subretinal space of one eye of Brown Norway male rats using a standardized protocol. A high dose (200 mg/kg) and a low dose (100 mg/kg) of the CCR2 antagonist PFE-0409, or vehicle control, was administered by oral gavage (BID) beginning either on day 1 (for prophylactic regimen) or day 15 (for therapeutic regimen) (N=8 animals/group). A VEGFR tyrosine kinase inhibitor positive control was administered intraperitoneally twice daily (N=8, both regimens). On day 22, animals were euthanized at either 2 or 14 hours post-dose. Blood and retina tissue from the non-laser treated eye was collected for compound measurement. CCR2 target modulation was quantitated via the inhibition of binding of fluorescent-labeled mouse JE-1 ligand binding in blood cells using flow cytometric detection. Laser-treated eyes were removed, processed and stained overnight with FITC-isolectin B4. The RPE-choroid-sclera complex was flat-mounted for fluorescence microscopy, and images were analyzed to calculate neovascular area.
Results: :
PF-0409 treatment produced >90% inhibition of ligand binding to CCR2 in whole blood cell samples collected two hours after oral administration. Target inhibition on blood cells at trough (14 hours) was dose-dependent, with significant inhibition maintained (≥85%) at the high dose. Compound concentrations in retinal tissue exceeded those in serum at both peak and trough time points. No significant changes in animal body weights were observed. Prophylactic PF-0409 treatment reduced neovascular lesion area at day 22 by 17% (p=.052) and 23% (p=.010) at the low and high dose, respectively. In the study in which PF-0409 treatment was delayed until day 15, there was no effect on neovascularization. VEGFR TKI was effective in both preventive and delayed dosing regimens (58% vs. 41% inhibition, respectively).
Conclusions: :
Continuous pharmacologic inhibition of CCR2 target function from the time of laser stimulus significantly reduced rat choroidal neovascularization, a result consistent with earlier published reports conducted in knockout mice. Delayed treatment with CCR2 inhibitor was not efficacious, suggesting the potential clinical benefits in targeting this receptor for CNV may be limited to disease prevention.
Keywords: age-related macular degeneration • choroid: neovascularization • inflammation