A promising future for peptides in ophthalmology: work effectively and smartly.

Despite progress in pharmacological modalities, treatments for ocular diseases are inconvenient, traumatic, costly and often end in poor final visual results. Peptides, considered as protein fragments, can adequately mimic protein binding and thus are used as therapeutic agents. Chemical modifications and bioengineering techniques are being frequently introduced to improve efficacy and stability of peptides, thereby improving their druggability. Cell-penetrating peptides (CPPs), peptides characterized by penetrating plasma membrane, are famous barrier- passers. They are good candidates for carrying drugs through ocular barriers. Therapeutic peptide and CPP perfectly complement each other. Once united, they may form an optimal formula for ocular topical administration, which can work both effectively and smartly. The consequent noninvasive delivery and economical cost would actualize prophylactic intervention, early treatment and long-term therapy to avoid chronic irreversible vision loss. The aim of the current review is a) to summarize recent therapeutic peptides, both anti-angiogenic and anti-inflammation, evidenced by animal experiments in vivo; b) to discuss the discovery strategies for therapeutic peptide; c) to present current delivery strategies for ophthalmic therapeutic peptide; and d) to introduce CPPs which are capable to deliver cargos to intraocular space via ocular surface administration.