Using Cell-Penetrating Peptides to Deliver Drugs Inside Cells for Inflammation and Oxidative Stress Diseases | Research

The takeaway

Cell-penetrating peptides can ferry therapeutic proteins and peptides into cells to fight oxidative stress, inflammation, and cell death, but safety and specificity issues must be resolved before clinical use.

4 key barriers to clinical use
Nonspecificity, proteolytic instability, potential toxicity, and immunogenicity remain the main obstacles for cell-penetrating peptide delivery systems

What the researchers found

The review found that CPPs have been successfully used in both laboratory and animal studies to deliver therapeutic peptides and proteins that target three key disease processes: oxidative stress (cellular damage from reactive molecules), inflammatory response (the immune system's overreaction), and apoptosis (programmed cell death).

However, the authors identified four fundamental obstacles preventing clinical use: CPPs lack specificity (they enter healthy and diseased cells alike), they are unstable in the body (enzymes break them down), they may be toxic at effective doses, and they can trigger immune responses. The review concludes that more research is needed to overcome these limitations before CPP-mediated delivery can be used in patients.

Why it matters

A huge number of therapeutic peptides and proteins have been identified that could treat conditions from neurodegenerative diseases to chronic inflammation — but many of them can't get inside cells where they need to work. Cell-penetrating peptides offer a potential universal delivery solution. If the challenges of specificity and safety can be solved, CPP technology could unlock an entire class of intracellular peptide therapies that are currently stuck in the lab.

The numbers in context

Review covers in vitro and in vivo studies · 3 disease mechanisms targeted (oxidative stress, inflammation, apoptosis) · 4 key CPP limitations identified

How the study worked

This is a narrative review article that surveyed the published scientific literature on cell-penetrating peptide-mediated delivery of therapeutic peptides and proteins. The authors examined studies covering in vitro (cell culture) and in vivo (animal) applications, focusing specifically on diseases involving oxidative stress, inflammatory pathways, and apoptosis.

Who was studied

Review of in vitro and in vivo studies (no direct patient population)

What this study cannot tell us

As a narrative review, this paper synthesizes existing literature but does not generate new data or perform systematic quality assessment of the studies it covers. The conclusions are only as strong as the individual studies reviewed. Publication bias may favor positive CPP results. The review does not quantify efficacy across studies or provide meta-analytic evidence.

How to read the evidence

Rated 'moderate' because this is a comprehensive review covering multiple in vitro and in vivo studies, but it is a narrative review without systematic methodology or meta-analysis, and the field lacks human clinical trial data.

When this study was published

Published in 2022 in the Journal of Pharmacy and Pharmacology. CPP research continues to advance rapidly, with newer studies exploring targeted CPP variants and combination delivery systems.

The bigger picture

This review sits at the intersection of peptide therapeutics and drug delivery — two of the fastest-growing areas in pharmaceutical research. As more peptide drugs are discovered, the delivery problem becomes the bottleneck. CPPs represent one of several competing approaches (alongside nanoparticles, liposomes, and conjugation strategies) to solving intracellular delivery. Progress in making CPPs more specific and stable could transform how peptide medicines are administered.

Questions still open

Can CPPs be engineered with targeting ligands to deliver cargo specifically to diseased cells while sparing healthy tissue?
Which of the four identified CPP limitations — nonspecificity, instability, toxicity, or immunogenicity — is the biggest barrier to clinical translation?
How do CPP delivery approaches compare to other intracellular delivery methods like lipid nanoparticles or antibody-drug conjugates?

Common questions

What are cell-penetrating peptides and how do they work?

Cell-penetrating peptides (CPPs) are short chains of amino acids (typically 5-30 residues) that have the ability to cross cell membranes. They can carry larger therapeutic molecules — like proteins or peptide drugs — into cells that would otherwise be inaccessible. Think of them as molecular delivery trucks that can pass through cellular walls.

Why can't therapeutic peptides just enter cells on their own?

Cell membranes are designed to be selective barriers. Most therapeutic peptides and proteins are too large, too charged, or too water-soluble to pass through the fatty cell membrane on their own. Without a delivery mechanism like CPPs, these drugs stay outside the cell and can't reach their intracellular targets.

Read the original research

Cell-penetrating peptide-mediated delivery of therapeutic peptides/proteins to manage the diseases involving oxidative stress, inflammatory response and apoptosis.

The Journal of pharmacy and pharmacology, 74(8), 1085-1116

View on PubMed ↗Publisher’s paper ↗

Citation

Sadeghian, Issa; Heidari, Reza; Raee, Mohammad Javad; Negahdaripour, Manica. (2022). Cell-penetrating peptide-mediated delivery of therapeutic peptides/proteins to manage the diseases involving oxidative stress, inflammatory response and apoptosis.. The Journal of pharmacy and pharmacology, 74(8), 1085-1116. https://doi.org/10.1093/jpp/rgac038