Safety and efficacy of a new eye drop formulation of spironolactone in a rat model of glucocorticoid-induced delay in corneal wound healing

Abstract

Purpose : Overactivation of the mineralocorticoid receptor (MR) increases inflammation, angiogenesis and fibrosis and has been reported to contribute to pathological changes in ocular diseases. We previously showed that topical administration of MR antagonist spironolactone (SPL) prevented glucocorticoid-induced delay in corneal wound healing in rabbit. We developed a new medical-grade polymer free eye drop formulation of SPL. The purpose of this study was to evaluate the ocular safety of this formulation and its efficacy in corneal re-epithelialization delayed by glucocorticoid in rat eyes.

Methods : Adult male Lewis rats were used to assess the ocular safety. Eye drops of SPL or placebo were administered once or 3 times daily for 7 days. Rats were euthanized, and eyes removed for corneal histology and immunostaining of inflammation (IBA1, ED1) and oxidative stress (Nitrotyrosine). To evaluate the efficacy, corneal wound of 4 mm diameter was created in rat eyes. Rats were divided into 4 groups: 1) topical dexamethasone (DEX, Dexafree 0.1%), 2) coadministration of DEX and SPL eye drops, 3) coadministration of DEX and placebo, and 4) without treatment. All treatments were administered 3 times daily for 3 days. At 24 and 48 hrs, corneal morphology was assessed in vivo using Micron III optical coherence tomography (OCT), and corneal re-epithelialization was observed by fluorescein staining under slit lamp. At day 3, eyes were collected for immunofluorescence and corneal nerves analysis.

Results : The SPL eye drop formulation was well tolerated. No redness or inflammation was observed. The morphology of corneal epithelium, stroma and endothelium remained unchanged. IBA1, ED1 and Nitrotyrosine immunofluorescence were all negative. In rat wound healing model, DEX induced a significantly delay in corneal wound healing at 24 hrs compared to the control group. OCT didn’t show any difference in corneal thickness. Both SPL and placebo improved corneal wound healing delayed by DEX, but the wound size was not significantly different between both groups at 24 hrs. Corneal re-innervation was not complete in all groups.

Conclusions : The new SPL formulation showed good ocular safety. Corneal wound healing should be observed at earlier time points at 6 and 12 hrs which would be more optimal for efficacy evaluation. The quality of corneal re-innervation will be further analyzed.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.