Generation of an anti-idiotypic masking domain for the construction of an affibody-based EGFR-targeting prodrug

Systemic toxicity is a significant challenge faced when developing therapeutic agents for cancer. High endogenous expression of cancer biomarkers limits the efficacy and safety of targeted therapies. The epidermal growth factor receptor (EGFR) is commonly overexpressed in certain cancers making it an interesting target for directed cancer therapy, but the potential is limited by the presence in healthy tissues. Conditional activation of targeted drugs can be achieved by utilizing the unique microenvironment of tumours. Proteases are important for tumorigenesis and are often upregulated in cancer. The design of a therapeutic agent that is selectively activated by tumor-associated proteases can improve the efficacy and safety by lowering systemic exposure. We have generated an anti-idiotypic masking domain with specificity for the binding surface of an EGFR-targeting affibody molecule using staphylococcal display. We found that the masking domain abrogates EGFR-binding in a proof-of-concept prodrug construct and that protease-mediated removal of the masking domain restores binding to EGFR. These results suggest that introducing an anti-idiotypic masking affibody domain is a viable approach for blocking EGFR-binding and warrants further studies evaluating the therapeutic applicability both in vitro and in vivo.
QC 20220316