In this work, we hypothesized that conjugation of the engineered multifunctional peptide adaptors to sunitinib for delivery to the posterior segment using the gel-forming eye drop would provide even more prolong therapeutic effects in the posterior tissues. We observed that the HR97-sunitinib conjugate had increased binding capacity to ocular melanin and was cleaved by proteases to release free sunitinib in vitro. Rats were dosed topically with HR97-SunitiGel once daily for seven days, followed by optic nerve head crush at various times after the last dose to assess the duration of RGC protection. We observed that the HR97-SunitiGel showed prolonged neuroprotective effects for up to 2 weeks after the last topical dose, whereas the protective effect of SunitiGel was only observed at 1 week after the last dose. Our observations support the potential for improving and prolonging therapeutic delivery to the posterior segment tissues by addressing multiple barriers to drug delivery and retention in the eye.

In this work, we hypothesized that conjugation of the engineered multifunctional peptide adaptors to sunitinib for delivery to the posterior segment using the gel-forming eye drop would provide even more prolong therapeutic effects in the posterior tissues. We observed that the HR97-sunitinib conjugate had increased binding capacity to ocular melanin and was cleaved by proteases to release free sunitinib in vitro. Rats were dosed topically with HR97-SunitiGel once daily for seven days, followed by optic nerve head crush at various times after the last dose to assess the duration of RGC protection. We observed that the HR97-SunitiGel showed prolonged neuroprotective effects for up to 2 weeks after the last topical dose, whereas the protective effect of SunitiGel was only observed at 1 week after the last dose. Our observations support the potential for improving and prolonging therapeutic delivery to the posterior segment tissues by addressing multiple barriers to drug delivery and retention in the eye.

Sustained drug delivery strategies have many potential benefits for treating a range of diseases, particularly chronic diseases that require treatment for years. For many chronic ocular diseases, patient adherence to eye drop dosing regimens and the need for frequent intraocular injections are significant barriers to effective disease management. Here, we utilize peptide engineering to impart melanin binding properties to peptide-drug conjugates to act as a sustained-release depot in the eye. We develop a super learning-based methodology to engineer multifunctional peptides that efficiently enter cells, bind to melanin, and have low cytotoxicity. When the lead multifunctional peptide (HR97) is conjugated to brimonidine, an intraocular pressure lowering drug that is prescribed for three times per day topical dosing, intraocular pressure reduction is observed for up to 18 days after a single intracameral injection in rabbits. Further, the cumulative intraocular pressure lowering effect increases ~17-fold compared to free brimonidine injection. Engineered multifunctional peptide-drug conjugates are a promising approach for providing sustained therapeutic delivery in the eye and beyond.