Construction and evaluation of a novel Stx2a-based immunotoxin against epidermal growth factor receptor (EGFR)

Immunotoxins (ITs) are chimeric proteins that combine the targeting specificity of a monoclonal antibody or antibody fragment with the cytotoxic properties of a toxin. They offer a promising strategy for cancer therapy by selectively delivering cytotoxic payloads to tumor cells. The epidermal growth factor receptor (EGFR) is frequently overexpressed in various cancers, making it an attractive target for IT-based therapies.

In this study, we designed and constructed a novel IT composed of a single-chain variable fragment (scFv) derived from Panitumumab, a humanized monoclonal antibody targeting EGFR, and the Shiga toxin A subunit 2 (Stx2a), a potent cytotoxic agent. The IT was designed using computational tools to optimize the linker region between the scFv and Stx2a domains. The recombinant IT was expressed in a prokaryotic host and purified to homogeneity.

The cytotoxic activity of the IT was evaluated in vitro against human colorectal carcinoma (HCT-116) and human embryonic kidney (HEK293) cells. The IT demonstrated significant cytotoxicity against HCT-116 cells, while exhibiting minimal toxicity to non-target cells. To enhance the delivery and efficacy of the IT, we encapsulated it in chitosan nanoparticles. The nanoparticle-based formulation showed improved cellular uptake and enhanced cytotoxicity compared to the free IT.

Our findings suggest that the designed IT has the potential to be a promising therapeutic agent against EGFR-expressing cancers. Further studies are warranted to evaluate its efficacy in vivo and to optimize its formulation for clinical applications.