Abstract 4471: AD-O64.4 - a novel bioconjugate for tumor-targeted drug delivery

Although standard chemotherapy is still one of the most effective treatment for many types of cancer - often causes side effects. Chemotherapeutic agents primarily damage cancer cells with a rapidly dividing and growing profile, thereby also destroy healthy cells with such characteristics, which leads to side effects. Scientists are continually working to identify new, safer drugs, methods of administering chemotherapy, and combinations of existing treatments that have fewer side effects. In recent years, drug delivery systems (DDS) based on a concept of conjugation anticancer agents to carrier protein have been developed, achieving a better clinical response and tolerability. Protein-drug conjugates represent a whole new concept for cancer treatment which, although highly effective, cause much fewer sides effects than traditional chemotherapy. The present work is aimed to create a new conjugate molecule which essentially demonstrates greater effect than the summarized effects of its components due to specific targeting to cancer cells. We generated AD-O64.4 complex molecule, consisting of fusion protein INF- γ - TRAIL/Apo2L conjugated with the anti-mitotic agent SN-38 via the thioether linker. Carrier protein is a fusion molecule which is composed of soluble fragment of TRAIL (acting as a targeting carrier and effector) fused with artificial dimer of IFN-γ (acting as effector). SN-38, a topoisomerase I inhibitor with low nanomolar potency, the active metabolite of irinotecan, cannot be given directly to patients because of its toxicity and poor solubility. Linking SN-38 to the carrier fusion protein results in selective drug delivery to tumors which consequently leads to increased amount of the drug reaching the tumors and minimized damage of healthy cells. Analysis of the conjugate was performed by LC-MS and resulted in determination of drug-protein ratio. Agregation studies of the molecule complex were conducted by DLS and fluorescent protein aggregation assay. Cytotoxicity was evaluated with MTT assay and efficacy was performed on female SCID mice xenograft model bearing Human Uterine Sarcoma (MES-SA/Dx5). Our results show an effective process of conjugation of anticancer compound SN-38 to the carrier protein which leads to formation of an active complex with enhanced efficacy. AD-O64.4 exhibited cytotoxic effect on various cancer cell lines, (IC50 about 10 ng/ml), but showed no toxic effect on normal cells. This conjugate was also highly cytotoxic aga