Abstract: The present invention provides constructs comprising a plurality of peptides capable of targeting at least two different extracellular tumor antigens and a toxin, optionally connected to an organic scaffold. Use of such constructs in treating cancer are provided as well. The invention also provides particular peptides binding certain extracellular tumor antigens as well as toxins having antitumor activity.

Abstract: A system of a recombinant bacteriophage library and a target of interest complex, wherein the recombinant bacteriophage peptide library includes a plurality of peptides expressed on the surface of recombinant bacteriophages wherein each recombinant bacteriophage includes (a) a pill protein; wherein each pill protein includes (b) a peptide or polypeptide involved in an intermolecular interaction, which differs by at least one amino acid from other peptides or polypeptides in the library; and (c) a modified protease cleavage site proximal to the peptide, wherein the modified protease cleavage site is the same in each bacteriophage, the modified cleavage site having a reduced binding affinity to a protease, as compared to a non-modified cleavage site, and wherein the target of interest complex includes a protease, a flexible linker attached to the protease, and a target of interest attached to the flexible linker, wherein the target of interest participates in an intermolecular interaction.