As per the claim by the authors, siRNA, works by preventing the gene with the mutation from being expressed but permitting the healthy keratin genes to function normally. The study marked the first time that the skin of a human subject was treated with this type of drug. Researchers say that in this single patient trial the drug worked, had no serious side effects, and has vast potential because of its ability to specifically and potently target single molecules, making it an option for many other genetic diseases, including cancer.
The patient was treated with siRNA on her right foot and with placebo on the left foot. The callus on the right foot that received the siRNA fell off at the site of injection, but this did not happen on the left foot. Congrats for this remarkable achievement...
Source : http://healthcare.utah.edu/dermatology/about/faculty/sancyleachman.html