Multifunctional PEG Retinylamine Conjugate Provides Prolonged Protection against Retinal Degeneration in Mice

[Image: see text] A polyethylene glycol (PEG) retinylamine (Ret-NH(2)) conjugate PEG-GFL-NH-Ret with a glycine-phenylalanine-leucine (GFL) spacer was synthesized for controlled oral delivery of Ret-NH(2) to treat retinal degenerative diseases, including Stargardt disease (STGD) and age-related macular degeneration (AMD). The peptide spacer was introduced for sustained release of the drug by digestive enzymes in the gastrointestinal tract. The pharmacokinetics experiments showed that the PEG conjugate could control the sustained drug release after oral administration and had much lower nonspecific liver drug accumulation than the free drug in wild-type female C57BL mice. In the mean time, the conjugate maintained the same concentration of Ret-NH(2) in the eye as the free drug. Also, PEG-GFL-NH-Ret at a Ret-NH(2) equivalent dose of 25 mg/kg produced complete protection of Abca4(–/–)Rdh8(–/–) mouse retinas against light-induced retinal degeneration for 3 days after oral administration, as revealed by OCT retina imaging, whereas free Ret-NH(2) did not provide any protection under identical conditions. The polymer conjugate PEG-GFL-NH-Ret has great potential for controlled delivery of Ret-NH(2) to the eye for effective protection against retinal degenerative diseases.