New compounds show promise in treating retinitis pigmentosa

Two new compounds may be able to treat retinitis pigmentosa, a group of inherited eye diseases that cause blindness. The compounds, described in a study published January 14^th in the open-access journal PLOS Biology by Beata Jastrzebska from Case Western Reserve University, US, and colleagues, were identified using a virtual screening approach.

In retinitis pigmentosa, the retina protein rhodopsin is often misfolded due to genetic mutations, causing retinal cells to die off and leading to progressive blindness. Small molecules to correct rhodopsin folding are urgently needed to treat the estimated 100,000 people in the United States with the disease. Current experimental treatments include retinoid compounds, such as synthetic vitamin A derivatives, which are sensitive to light and can be toxic, leading to several drawbacks.

In the new study, researchers utilized virtual screening to search for new drug-like molecules that bind to and stabilize the structure of rhodopsin to improve its folding and movement through the cell. Two non-retinoid compounds were identified which met these criteria and had the ability to cross the blood-brain and blood-retina barriers. The team tested the compounds in the lab and showed that they improved cell surface expression of rhodopsin in 36 of 123 genetic subtypes of retinitis pigmentosa, including the most common one. Additionally, they protected against retinal degeneration in mice with retinitis pigmentosa.

"Importantly, treatment with either compound improved the overall retina health and function in these mice by prolonging the survival of their photoreceptors," the authors say. However, they note that additional studies of the compounds or related compounds are needed before testing the treatments in humans.

The authors add, "Inherited mutations in the rhodopsin gene cause retinitis pigmentosa (RP), a progressive and currently untreatable blinding disease. This study identifies small molecule pharmacochaperones that suppress the pathogenic effects of various rhodopsin mutants in vitro and slow photoreceptor cell death in a mouse model of RP, offering a potential new therapeutic approach to prevent vision loss."