Cell-penetrating peptides can ferry drugs across the eye's biological barriers, potentially enabling topical delivery of treatments that currently require invasive eye injections.
Topical delivery to posterior eyeCPP-conjugated FDA-approved drugs have reached the back of the eye through topical application in animal models, potentially replacing intravitreal injections.
What the researchers found
Cell-penetrating peptides can be conjugated with FDA-approved drugs to deliver them to the posterior segment of the eye via topical application, as demonstrated in animal models. This approach could reduce or eliminate the need for frequent intravitreal injections currently required for retinal diseases. The review catalogues various CPP types, their mechanisms of membrane translocation, and emerging peptide-based therapeutics for ocular conditions.
Why it matters
Millions of people with retinal diseases like age-related macular degeneration require frequent intravitreal injections — a procedure that is uncomfortable and carries risks including infection and retinal detachment. If CPPs can deliver these same drugs via eye drops, it would transform treatment accessibility, compliance, and safety for patients with chronic eye conditions.
How the study worked
This is a systematic review synthesizing literature from PubMed searches and clinical trial databases on cell-penetrating peptides, peptide-based ocular drugs, and CPP-mediated drug delivery systems for eye diseases.
What this study cannot tell us
As a review, this paper does not present original experimental data. Most CPP ocular delivery evidence comes from animal models, and translation to human eyes — which differ in size and barrier properties — remains to be validated. The review does not provide a quantitative comparison of CPP delivery efficiency versus intravitreal injection, making it difficult to assess how close this technology is to clinical viability.
How to read the evidence
This is a review article summarizing preclinical and early clinical evidence. While it provides a comprehensive overview of the field, the primary evidence for CPP ocular delivery comes from animal studies, not human clinical trials.
When this study was published
Published in 2023, this review captures the state of the art in CPP ocular delivery research during a period of rapid advancement in peptide-based drug delivery technologies.
The bigger picture
Cell-penetrating peptides represent one of the most active areas of peptide research in drug delivery. While CPPs have been explored for many applications including cancer therapy and brain delivery, the eye presents a particularly compelling use case because current alternatives (injections) are invasive and the barrier challenges are well-defined. Success here could accelerate CPP adoption across other difficult-to-reach therapeutic targets.
Questions still open
- Can CPP-mediated topical delivery achieve drug concentrations at the retina comparable to intravitreal injection in humans?
- What are the long-term safety profiles of repeated CPP exposure to ocular tissues?
- Which specific CPP sequences are most effective for crossing the particular barriers of the human eye?
Common questions
What are cell-penetrating peptides and how do they work?
Why is delivering drugs to the back of the eye so difficult?
Read the original research
Ocular Delivery of Therapeutic Agents by Cell-Penetrating Peptides.
Cells, 12(7)
Citation
Nhàn, Nguyễn Thị Thanh; Maidana, Daniel E; Yamada, Kaori H. (2023). Ocular Delivery of Therapeutic Agents by Cell-Penetrating Peptides.. Cells, 12(7). https://doi.org/10.3390/cells12071071