Delivery Advance Illustrates Influence of Cosmetics Skin RNAi Therapeutics

The skin has always been a target organ of considerable interest to the RNAi Therapeutics industry due to its apparent accessibility for delivery purposes plus the fact that there are various unmet needs ranging from the severe genetic disease (e.g. epidermolysis bullosa, pachyonycia congenita) to cosmetic desires.  Interestingly, it is the latter that in many ways is driving skin RNAi Therapeutics these days.

Motorized microneedle array with unprecedented silencing efficacy

    

In an important advance in the rate-limiting area of delivery, Hickerson and colleagues from TransDerm and various other collaborators recently published 80% gene silencing efficacy in a mouse model for epidermal gene expression using a motorized microneedle array borrowed from the cosmetics industry (in particular the Triple-Mby BomtechElectronics of cosmetics hot-spot South Korea).  This compares to 50% and 33% gene silencing in the same model using simple (static) microneedle arrays and intradermal needle injection, respectively, before.  Accordingly, this represents a 2.5 to 3.5-fold increase in gene silencing efficacy when considering how much of the undesired target protein you are left with!

I have to admit that I did not double-check that indeed the same siRNA sequences and self-delivering RNAi trigger modifications were used in the various studies which could have affected results.  However, since these results have all been reported by TransDerm and the goal of TransDerm was to compare delivery efficacies of various technologies, I am willing to accept the comparability claim by the authors. _­

The trick with the motorized microneedle array appears to be that following penetration of the stratum corneum barrier motion (oscillation) allows for a larger volume of drug to be deposited in the epidermis than with a static needle array.  Moreover, the depth of administration can be adjusted for optimal epidermal delivery and to make it pain free as well, unlike the original high-pressure hypodermic needle attempts by TransDerm.   With this, it should be possible to deposit low single-digit milligram of RNAi triggers to an area the size of a tip of a thumb- which is quite a bit.

A possible limitation of such microneedle arrays is that the administration itself causes microinjuries to the skin.  Therefore, you want to make sure that you do not end up making things worse, especially in applications where wound healing and restoration are the goal.  Since the technology is apparently used in the beauty industry already, it is unlikely that its application will leave insightly scars and the likes.

I look forward to seeing a technology like motorized microneedle arrays in conjunction with self-delivering RNAi trigger formats being used in the clinic.  Initially, the technology is most amenable to applications where the focus is on locally defined areas such a skin parts prone to blistering.  However, taking advantage of imaging technologies and 3-D printing, I envision a future in which the technology would also be possible to treat large areas of the skin, if not the entire body surface.  As TransDerm illustrates, combining the capabilities of existing technologies from disparate areas often enables the biggest advances.

RXI-109 for dermal anti-scarring now available under the ‘Specials’ provision in the EU

Anybody that has gone to a dermatologist knows how blurred the lines between medical and cosmetic applications have become when it comes to the skin (cosmeceutical concept).  Taking advantage of the regulatory grey zone, it is skin applications that are leading the charge in the commercialization of RNAi gene silencing in WoMan.  Following a claimed treatment for skin blemishes marketed as Britena Whitening & Anti-blotch Cream by Biomics (partnered with Benitec on HepB), it is now RXi Pharmaceuticals that has signed a distribution agreement for its dermal anti-scarring drug candidate RXI-109 with Ethicor. 

The goal of this arrangement is to drive early sales based on an exception of European drug legislation that allows for the use of experimental drugs prior to proper marketing authorization.  All it apparently takes is a judgment call by the treating physician.  I can see the point of this ‘Specials’ provision for severe, orphan diseases as a form of compassionate use when there is intriguing early clinical evidence of efficacy and safety, but for an anti-scarring treatment, mmh...you can easily see how consumers willing to take risks in the quest for beauty will make their physician give them an injection of the stuff.

But then again, when you see how much unproven, potentially harmful potions and lotions are being sold on the cosmetics market, it is hard to argue why you should make an exception with RNAi as long as care is being taken that somewhat riskier (depending on chemistry) systemic exposures remain low and yours truly does not have to pay for it via increased insurance premiums.  I guess my biggest problem with all this is that the company distributing RXI-109 calls itself ‘Ethicor’ just as I get nervous when somebody starts a sentence with ‘to be honest’ and what follows is more often than not a lie.