To understand the mechanism of action of cytokines on immune cells and cancer cells we have discovered that a variety of solid tumor cell lines express chemical docking ports (receptors) for immune regulatory cytokines that attach to these receptors. These receptors are over expressed on cancer cells compared to normal immune cells. Therefore, we have designed and produced novel cancer therapeutics in which a toxin derived from a bacterium is fused to cytokines such as interleukin-4 and interleukin-13. These recombinant proteins were produced in large quantities in E.coli. These proteins (termed IL-13-PE and IL-4-PE) will only attach to cancer cells through their receptors. Once bound, the whole complex is taken inside the cell and cell gets tricked into intoxication and dies. This targeted approach can be very useful for cancer therapy. These two targeted agents have been licensed to Biotechnology Companies, and CBER has established CRADAs with these Companies. Under these CRADA agreements, preclinical safety, efficacy and mechanism of action studies are being performed for further clinical development