Cell-specific drug targeting is the major goal of nanotechnology-based delivery platforms. New generation of drug delivery systems is being engineered to allow targeting of cell surface antigens. Polymers able to deliver specific inhibitory agents to tumor cells are important because they are less immunogenic than viral vectors and more useful for repetitive treatments needed for angiogenesis inhibition. A new prototype drug delivery system, a nanoconjugate Polycefin, was synthesized for targeted delivery of antisense oligonucleotides and antibodies into tumors. The delivery of antisense oligonucleotides to α4 and β1 chains of a vascular basement membrane protein, laminin-8, suppressed its synthesis in vivo. Treatment of glioma-bearing rats significantly reduced tumor vascularity (p<0.001) and increased animal survival (p<0.004).

MATERIAL AND METHODS: Polycefin consists of modules for endosomal uptake, endosomal membrane disruption, oligonucleotide release into the cytoplasm, protection from enzymatic degradation, and fluorescent dye Alexa 680 for imaging. Two anti-tumor antibodies were tested, tumor cell-specific anti-nuclear autoantibody 2C5, and anti-transferrin receptor (TfR) antibody. These components were covalently conjugated to poly(malic acid) (Mw 50000, Mw/Mn 1.3) from Physarum polycephalum. The presence of antibodies on Polycefin was confirmed by HPLC and ELISA. Human glioma and breast cancer cell lines were inoculated into nude mice. Polycefin variants were injected intravenously. Xenogen IVIS 200 Imager was used to detect and quantitate Polycefin accumulation in vivo.

RESULTS: Several Polycefin variants were tested 1. Polycefin with anti-mouse TfR antibody; 2. Polycefin with anti-human TfR antibody; 3. Polycefin with both antibodies to TfR; 4. Polycefin with autoantibody 2C5 alone, and 5. Polycefin with autoantibody 2C5 together with anti-mouse TfR. Drug accumulation was higher in brain and breast tumors than in normal non-tumor tissues. The highest tumor accumulation was achieved when the drug contained the combination of anti-mouse and anti-human TfR antibodies, or of anti-mouse TfR and human anti-nuclear autoantibody 2C5. These differences were significant (p<0.001).

CONCLUSIONS: Two antisense oligonucleotides blocking mRNAs of α and β chains of an invasive tumor marker, laminin-8, were delivered simultaneously using Polycefin to brain or breast tumor cells. In the xenogeneic mouse models used, the variant with the combination of mouse anti-TfR and human anti-TfR provides the most effective drug delivery through mouse endothelial system and into implanted human brain and breast tumor cells. Another efficient variant was Polycefin containing the combination of mouse anti-TfR and anti-nucleosome antibody 2C5. Presence of two or more different antibodies on Polycefin may be important for the efficacy of drug delivery and tumor treatment.

98th AACR Annual Meeting-- Apr 14-18, 2007; Los Angeles, CA