Recent development and optimization of pseudomonas aeruginosa exotoxin immunotoxins in cancer therapeutic applications

Recombinant immunotoxins are fusion proteins composed of a peptide toxin and a specific targeting domain through genetic recombination. They are engineered to recognize disease-specific target receptors and kill the cell upon internalization. Full-sized monoclonal antibodies, smaller antibody fragments and ligands, such as a cytokine or a growth factor, have been commonly used as the targeting domain, while bacterial Pseudomonas aeruginosa exotoxin (PE) is the usual toxin fusion partner, due to its natural cytotoxicity and other unique advantages. PE-based recombinant immunotoxins have shown remarkable efficacy in the treatment of tumors and autoimmune diseases. At the same time, efforts are underway to address major challenges, including immunogenicity, nonspecific cytotoxicity and poor penetration, which limit their clinical applications. Recent strategies for structural optimization of PE-based immunotoxins, combined with mutagenesis approaches, have reduced the immunogenicity and non-specific cytotoxicity, thus increasing both their safety and efficacy. This review highlights novel insights and design concepts that were used to advance immunotoxins for the treatment of hematological and solid tumors and also presents future development prospect of PE-based recombinant immunotoxins that are expected to play an important role in cancer therapy.