In Vitro and In Vivo Ocular Safety Assessment of Pexidartinib

Background: Pexidartinib (PLX3397), a small-molecule kinase inhibitor, has shown therapeutic potential in experimental ocular inflammatory and retinal degenerative disease models following oral administration; however, its intravitreal (IVT) safety remains unknown. As IVT delivery enables direct retinal targeting, this study aims to evaluate the IVT safety profile of pexidartinib using in vitro and in vivo models. Methods: In vitro safety of pexidartinib was evaluated in adult retinal pigment epithelial cells (ARPE-19), 661W, human corneal epithelial (HCE), and N9 cell lines using the MTT assay. In vivo safety was assessed in rats following IVT administration of pexidartinib at 100 n M , 10 μ M , and 100 μ M . Ocular safety was evaluated using slit-lamp biomicroscopy, intraocular pressure (IOP) measurements, RT-qPCR, histology, and immunofluorescence. Results: Pexidartinib was well tolerated in ARPE-19, 661W, HCE, and N9cells up to 10 μ M , while higher concentrations (50–100 μ M ) reduced cell viability in all cell lines except in 661W cells. In vivo , slit-lamp examination and IOP measurements showed no detectable changes postinjection across all tested concentrations. Histological and immunofluorescence evaluation demonstrated preserved retinal and corneal layers, with no significant increase in retinal Caspase-3 expression. Furthermore, RT-qPCR analysis showed minor alterations, predominantly at the low dose (100 n M ), compared with the higher doses (10 and 100 μ M ); however, these changes were not associated with structural or apoptotic degeneration, possibly indicating nonmonotonic dose responses for various kinase inhibitors. Conclusion: IVT pexidartinib was well tolerated in both in vitro (10 μ M ) and in vivo (100 μ M ). These findings support the potential development of pexidartinib as a localized therapy for treating posterior segment eye diseases. However, further long-term studies on ocular safety, pharmacokinetics, and efficacy are warranted.