Safety and efficacy of a new intraocular spironolactone suspension in a rat model of laser-induced choroidal neovascularization and fibrosis

Abstract

Purpose : Choroidal neovascularization (CNV) and fibrosis lead to severe vision loss in patients with wet age-related macular degeneration (AMD). Current anti-VEGF treatments improve visual prognosis of wet AMD, but do not target fibrosis nor have effect on retinal pigment epithelium (RPE) regeneration, compromising long-term retinal viability. We previously showed that spironolactone (SPL), a mineralocorticoid receptor antagonist, reduced signs of CNV in patients refractory to anti-VEGF, and that SPL inhibited CNV through a VEGF-independent mechanism. The aim of this study was to assess the ocular safety of a new intraocular SPL suspension and to evaluate its efficacy on CNV, fibrosis and RPE integrity.

Methods : Lewis rats were used to study the ocular tolerance. A single intravitreal injection of SPL suspension or placebo (PBO) was performed in both eyes. Retinal morphology was assessed in vivo on D7 by optical coherence tomography (OCT) and ex vivo on D30 by histology. Eyes were also used for immunofluorescence (IF) of cell death (TUNEL), inflammation (IBA1, GFAP) and photoreceptors (cone-arrestin, rhodopsin). Long-Evans rats were used to evaluate the efficacy. Laser photocoagulation was performed twice on D0 and D7. SPL suspension or PBO was injected in both eyes on D0 and D14. FA and ICGA were conducted on D14 and D28 to assess CNV leakage. Rats were euthanized on D30, and RPE/Choroid flat-mounts used for analysis of fibrosis (collagen 1) and RPE coverage (RPE65, phalloidin).

Results : OCT and histology showed normal retinal morphology in both SPL and PBO groups. No TUNEL-positive dead cells were detected; GFAP was not activated; no additional activation of IBA1-positive microglia was observed in both groups. Cone-arrestin and rhodopsin IF showed no photoreceptor damage. In CNV model, SPL significantly reduced CNV FA leakage on D14 and D28 compared to the PBO (P<0.0001). SPL also remarkably decreased collagen 1-positive fibrotic deposits on the CNV lesions (P<0.0001). Phalloidin and RPE65 staining showed that SPL improved RPE differentiation and coverage on CNV lesions compared to the PBO (P<0.0001).

Conclusions : Intraocular SPL suspension showed good ocular safety and effectiveness in reducing CNV leakage and fibrosis. Moreover, it improved RPE coverage and barrier function. This new formulation is a promising medical-grade treatment for wet AMD patients.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.