Cosmeceutical peptides; generic vs. brand

February 1, 2005

Peptides clearly represent the most novel active in the current cosmeceutical market.

Q. Are there several different types of cosmeceutical peptides?

Remember that peptides function as cellular communicators, providing instructions as to how various bodily structures are intended to function. To this end, cosmetic chemists have tried to design topical analogues to peptide fragments active in skin physiology.

Another category of peptides is thought to modulate function at the.neuromuscular junction. These are hexapeptides and septapeptides and do not have any functional relation to the collagen-modulating peptides. These larger peptides are designed to competitively bind to the SNARE complex at the neuromuscular junction. Remember that botulinum toxin A strongly binds to this complex, completely interrupting transmission across the neuromuscular junction. These peptides do not bind to the SNARE complex but rather competitively inhibit acetylcholine binding. They do not completely interrupt neurotransmission, but decrease the strength of the neuromuscular signal, thus decreasing and not.preventing muscle contraction. The theory is that the topical application of these peptides decreases the strength of facial muscle contraction, thus creating a botulinum toxin-like effect. Myoxinol (Cognis Group) and argiriline are commercialized peptides of this type.

The main question that comes to mind regarding these neuromuscular junction-modulating peptides is how their efficacy was demonstrated. As compared to the collagen-modulating peptides that were studied for their effect on confluent fibroblast cultures, these neuromuscular junction-modulating peptides were studied in skeletal muscle cultures. Skeletal muscle cultures have been observed to undergo a certain number of spontaneous contractions per unit time under normal conditions. When Myoxinol and argiriline were added to these skeletal muscle cultures, the number of spontaneous contractions per unit time was observed to decrease. Thus, it was concluded that these peptides decrease neuromuscular junction activities and have botulinum A toxin-like activity.

One of the key differences between the commercialized pentapeptides and the neuromuscular junction-modifying peptides is the addition of a penetration enhancer to Matrixyl. Palmitic acid is a potent penetration enhancer, perhaps allowing the peptide to actually reach a target site. Cutaneous penetration of peptides is problematic, since they are typically ionic and require some type of penetration enhancer to reach the desired target, which, in this case, is the viable epidermis and dermis. Larger peptides are more difficult to penetrate than smaller peptides. This has led to speculation as to whether Myoxinol or argiriline can actually reach the neuromuscular junction to affect competitive reversible transmitter inhibition.

In summary, peptides represent a fascinating theoretical method of modulating the skin function.

I believe this technology is still in its infancy and that enhanced efficacy will be achieved through better sophistication in peptide design and testing. Peptide manufacture shows promise for the treatment of diverse medical conditions such as Alzheimer's dementia, Parkinson's motor disease and multiple sclerosis. This is a key technology to watch for the future.

Q. Is there a difference between generic and brand name corticosteroids?

This is a frequent patient question, which is sometimes difficult to answer.