Rationally Designed, Short-Acting RPE65 Inhibitors for Visual Cycle-Associated Retinopathies

Area of Science:

• Biochemistry
• Ophthalmology
• Pharmacology

Background:

• The visual cycle is crucial for vision, but its byproducts can cause retinal toxicity, exemplified by Stargardt disease type 1 (STGD1).
• Emixustat, a visual cycle modulator (VCM) targeting RPE65, inhibits toxic bisretinoid production but has a prolonged duration of action causing visual impairment.

Purpose of the Study:

• To develop novel, short-acting VCMs with improved safety profiles.
• To investigate ester-containing emixustat analogs for tunable hydrolytic clearance and faster visual cycle recovery.

Main Methods:

• Synthesis of ester-containing emixustat analogs.
• Assessment of RPE65 targeting affinity and esterase-mediated metabolism.
• Evaluation of visual cycle recovery kinetics in vitro and in vivo.
• Testing efficacy in mouse models of photic retinopathy and STGD1.

Main Results:

• Ester analogs demonstrated tunable metabolism and maintained high-affinity RPE65 targeting.
• Compounds 6 (EYE-002) and 7 (EYE-003) showed faster visual cycle function recovery than emixustat.
• These novel VCMs provided protection against retinal degeneration in disease models.

Conclusions:

• Short-acting VCMs based on emixustat analogs offer a promising therapeutic strategy for retinal diseases.
• Tunable esterase-mediated clearance allows for optimized duration of action, potentially reducing visual side effects.
• These findings highlight the therapeutic potential of controlled visual cycle modulation for treating STGD1 and related retinopathies.