TransKingdom RNA™ interference (tkRNAi) is a broad-reaching platform that can be used to develop highly specific drug products for a diverse set of diseases. The tkRNAi platform involves the modification of bacteria to deliver shRNA to cells of the intestinal tract. A significant advantage of the tkRNAi platform is oral (by mouth) delivery making this platform extremely patient friendly while harnessing the full potential of the RNAi process. This is accomplished by engineering the bacteria for key attributes, as described in the figure below.
In Marina's drug product being developed for the treatment of Familial Adenomatous Polyposis, the bacterium is a live, non-pathogenic E.coli strain genetically modified to possess important novel properties:
- Production of high levels of shRNA, specific to β-catenin mRNA, so that each individual bacterium is able to deliver several copies of the shRNA upon each delivery event.
- An ability to efficiently enter epithelial cells lining the intestine. This is accomplished through the expression of the protein invasin on the outer surface of the bacteria. Invasin interaction with specific receptors (β1-integrins) on the outer membrane of the epithelial cells to facilitate intracellular uptake via an endosomal process.
- Release the shRNA within the cytoplasm of the epithelial cell. The protein listeriolysin O, also engineered into the bacterium, is a pore forming protein that selectively ruptures the endosome and releases the shRNA into the cytoplasm.
Once free in the cytoplasm of the epithelial cell, the shRNA is available for processing by the RNAi machinery to induce degradation (silencing) of β-catenin mRNA. The suppression of β-catenin protein has been shown to arrest or slow the growth of the intestinal cells responsible for polyp formation.