An approach to transdermal drug delivery that uses short,pulsed electric fields scored a 1,000-fold increase in conveyinglarge molecules through the skin, compared to a similar non-electric transdermal system, according to researchers.
The findings, presented by Massachusetts Institute ofTechnology (MIT) researchers to the Controlled Release Societyon Wednesday, open another potential avenue foradministering often large and fragile drug compounds beingdeveloped with biotechnology.
The MIT team reported their findings to a meeting in Orlando,Fla., on tests of three compounds of up to 1,000 molecularweight. That is larger than conventional drugs, but similar insize to some of the smallest potential therapeutic peptidesunder development.
"Even if this only worked with molecules of up to 1,000molecular weight, it would have clear commercial potential,"said Russell Potts, director of research.for Cygnus TherapeuticSystems Inc. of Redwood City, Calif.
The upper limit on the size of compounds that can betransported with electroporation is not yet known, said Potts,whose company has helped fund electroporation research inthe MIT laboratories of James Weaver and Robert Langer.Cygnus has an exclusive license to a U.S. patent issued last yearto MIT for electroporation. Langer also serves on Cygnus'scientific advisory board.
In in vitro tests using human skin and in vivo tests withhairless mice, electroporation showed the greatestimprovement over passive transdermal delivery of drugs, thatused in such commercial drug products as nicotine patches. The1,000-fold increase in compound-delivery was achieved usingone of the compounds in the in vitro study of human skin, Pottssaid. The rate of delivery in a rat study using a 650 molecularweight compound was between 50 and 100 times that of apassive transdermal sytem. The MIT team hopes to publish itsfindings in a journal within a few months.
Electroporation also bested another form of electrical transportknown as iontopheresis, which has been shown to an ability toforce a larger amount of drug compound through natural skinpores.
Electroporation differs in that its pulsed electric fields,milliseconds or less in duration, open reversible pathwaysthrough the outer skin layer, called the stratum corneum, Pottssaid. Compounds move through the skin, not just through skinpores.
A commercial drug product using electroporation is probably atleast five years away, Potts said. As for commercialapplications that Cygnus might pursue, "We really haven'tmade any long-term plans yet."
He said that one attractive possibility for such a drug-deliverysystem is insulin, which represents a huge potential market fora product that could supplant the frequent injections nowrequired by many diabetics. "I have no ability to predict thatthat's (technically) possible," Potts said.
However, he foresees the day when patients might strap on anbattery-powered electroporation drug-delivery system nolarger than today's portable infusion pumps.
Cygnus stock (NASDAQ:CYGN) closed Thursday at $15.50 ashare, up 25 cents.
-- Ray Potter Senior Editor
(c) 1997 American Health Consultants. All rights reserved.