After thirty years of promise and setbacks, a number of gene therapies for inherited immune disorders, like hemophilia, eye and neurodegenerative disorders, and lymphoid cancers have recently been approved in the United States and Europe or are anticipated to receive approval in the near future. One approach to gene therapy is to suppress the expression of specific proteins by gene silencing using siRNA. Viral delivery systems can have issues of immunogenicity and mutagenesis. This has stimulated the development of non-viral delivery systems. El-Sayed and collaborators based in Egypt and the USA have shown that chitosan complexed with fatty-acyl derivatives of a cationic cell-penetrating peptide, CGKRK, shows promise as a method for delivering intact short interfering RNA (siRNA) to breast cancer cells in vitro.