Abstract: The invention provides modified forms of bouganin protein having biological activity and a reduced propensity to activate human T cells as compared to the non-modified bouganin protein. The invention also provides T-cell epitope peptides of bouganin, and modified T-cell epitope peptides of bouganin which have a reduced propensity to activate human T cells as compared to the non-modified T-cell epitope peptide. The invention also provides cytotoxins having the having a ligand that binds to a cancer cells attached to the modified bouganin proteins. Also provided are methods of inhibiting or destroying mammalian cancer cells using the cytotoxins of the invention and pharmaceutical compositions for treating human cancer.

Abstract: The invention provides methods for generating fusion protein libraries, such as immunotoxin libraries. The invention also relates to libraries of recombinant cells encoding nucleic acid sequences comprising fusion proteins. In addition, the invention relates to the libraries themselves and the use of the libraries to screen for fusion proteins that are specific for target cells, such as cancer cells. Further, the invention relates to methods of improving fusion proteins and to the improved fusion proteins.