AbstractTargeted delivery remains one of the biggest challenges in the development of RNAi-based therapeutics. Cequent has developed a proprietary delivery technique for RNA interference, transkingdom RNAi (tkRNAi), in which non-pathogenic bacteria are engineered to invade specific target cells, produce and release short hairpin RNA (shRNA). We have previously shown tkRNAi to be successful in cell culture assays, in a mouse model for human colon cancer (APCmin), and in non-human primates (cynomolgus monkeys), by suppressing the oncogene, β-catenin. β-catenin is the key oncogene implicated in Colorectal Cancer (CRC) and Familial Adenomatous Polyposis (FAP); the latter being an orphan hereditary disease resulting in the formation of hundreds of polyps in the gastrointestinal tract and ultimately leads to the development of colon cancer without surgical intervention. No pharmaceutical treatment is available for patients with FAP. The non-human primate studies designed to evaluate on-target toxicities were conducted with a precursor (CEQ501) to our clinical candidate, CEQ508. Following optimization, which most importantly included platform engineering to improve hairpin production and processing, we conducted a large GLP mouse bridging toxicity study comparing off-target effects of CEQ508 and CEQ501. No CEQ508 or CEQ501-related adverse responses were identified in the following study parameters analyzed: clinical observations, body weights, serum chemistry, hematology, cytokines, gross or histopathology. As no test article-related changes were identified under the conditions of this study at the highest dose evaluated, the No Observed Effect Level (NOEL) for daily oral administration of either CEQ508 or CEQ501 was 5×109 cfu/day, or 2×1011 cfu/kg/day. (CEQ501 in non-human primates showed a similar safety profile with the No Observed Adverse Effect Level (NOAEL) determined to be 1×1012 cfu/day, or 2×1011 cfu/kg/day). Together with multiple internally conducted pharmacology and pharmacokinetic experiments, Cequent used this data in the nonclinical section of an IND filed in late 2009. In addition to presenting detailed in vivo data from our filing, an update on further development will be presented on CEQ508 for the proposed daily dosing of FAP patients with this oral tkRNAi therapeutic targeting β-catenin.Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4513.