Delivery of SAR 1118 to the retina via ophthalmic drops and its effectiveness in a rat streptozotocin (STZ) model of diabetic retinopathy (DR)

Abstract

Purpose: To determine the pharmacokinetics of SAR 1118, a small-molecule antagonist of leukocyte function-associated antigen (LFA)-1, after administration of ophthalmic drops in normal rats, and to determine its pharmacologic activity by assessing the inhibition of retinal leukostasis and vascular leakiness in a streptozotocin (STZ)-induced diabetic retinopathy model.

Methods: The ocular pharmacokinetics of SAR 1118 were studied in rats after a single topical dose of (14)C-SAR 1118 (1 mg/eye; 40 μCi; 15.5 μL). SAR 1118 concentration time profiles in plasma and ocular tissues were quantified by liquid scintillation counting (LSC). The pharmacologic activity of SAR 1118 eye drops administered thrice daily for 2 months at 1% (0.3 mg/eye/d) and 5% (1.5 mg/eye/d) was assessed in an STZ-induced diabetic rat model by determining retinal leukostasis and blood-retinal barrier breakdown. Diabetic rats treated with periocularly administered celecoxib microparticles served as the positive control, and vehicle-treated rats served as the negative control.

Results: A single dose of 6.5% (14)C-radiolabeled SAR 1118 ophthalmic drops delivered retinal drug levels greater than 1 μM in less than 30 minutes and sustained levels greater than 100 nM for 8 hours. SAR 1118 eye drops significantly reduced leukostasis and blood-retinal barrier breakdown in a dose-dependent manner.

Conclusions: SAR 1118 ophthalmic drops administered thrice daily deliver therapeutic levels of SAR 1118 in the retina and can alleviate the retinal complications associated with diabetes.

Figure 1.

Concentrations of radioactivity in ocular tissues at specified times after a single topical application of [¹⁴C]-SAR 1118 in male SD rats. Both eyes of normal SD rats (200–300 g body weight) were given a single topical application of radiolabeled [¹⁴C]-SAR 1118 at a dose of 1 mg/eye (40 μCi/eye, dose volume: 15.5 μL/eye). After 0.5, 2, 4, 8, 12, and 24 hours, the animals were killed, and the level radiolabeled drug was measured in various ocular tissues. The data represent the mean concentration of the drug in both eyes (n = 2 eyes) and are expressed as the nanogram equivalent of [¹⁴C]-SAR 1118 in the ocular tissues at specific time points.

Figure 2.

Concentrations of radioactivity in blood, plasma, and blood cellular fraction at specified times after a single topical application of [¹⁴C]-SAR 1118 in male SD rats. Both eyes of normal SD rats (200–300 g body weight) were given a single topical application of radiolabeled [¹⁴C]-SAR 1118 at a dose of 1 mg/eye (40 μCi/eye, dose volume: 15.5 μL/eye). After 0.083, 0.5, 2, 4, 8, 12, 24, and 72 hours, the level of the radiolabeled drug was measured in plasma, blood, and blood cells. The drug declined below the level of quantification beyond 12 hours after administration. The data represent the mean concentration of the drug (n = 3 rats; mean ± SD) and are expressed as the nanogram equivalent of [¹⁴C]-SAR 1118 at specific time points.

Figure 3.

Topical SAR 1118 reduced retinal leukostasis in the retinal vasculature of diabetic rats. (A) Representative images of adherent leukocytes in diabetic retinal vasculature as observed by confocal microscope. Arrows: adherent leukocytes. Magnification, ×20. (B) Total number of adherent leukocytes in the entire retina, isolated from the ipsilateral and contralateral eyes of normal (n = 4), diabetic (n = 5), diabetic+ vehicle (n = 6), diabetic+1% SAR1118 (n = 6), diabetic+5% SAR 1118 (n = 6), and diabetic+celecoxib microparticle (n = 4) treatment groups. (C) Retinal MPO activity in retinas isolated from the ipsilateral and contralateral eyes of normal (n = 6), diabetic (n = 6), diabetic+vehicle (n = 6), diabetic+1% SAR1118 (n = 6), diabetic+5% SAR 1118 (n = 6), and diabetic+celecoxib microparticle (n = 4) treatment groups. All treatments were applied to the ipsilateral eyes of diabetic animals, and the parameters were tested after 2 months of treatment. Data are expressed as the mean ± SD. *Significantly different from the diabetic group. †Significantly different from the vehicle-treated group.

Figure 4.

Topical SAR 1118 reduced the blood–retinal barrier breakdown in diabetic rats. (A) Retinal FITC-dextran leakage and (B) vitreous–plasma protein ratio of ipsilateral eye and the contralateral eye of normal (n = 6), diabetic (n = 6), diabetic+vehicle (n = 6), diabetic+1% SAR1118 (n = 6), diabetic+5% SAR 1118 (n = 6), and diabetic+celecoxib microparticle (n = 4) groups. Data are expressed as the mean ± SD. All treatments were applied to the ipsilateral eye of diabetic animals, and the parameters were tested after 2 months of treatment. *Significantly different from diabetic group. †Significantly different from the vehicle-treated group.