Exploiting intracellular oncogenic proteins to release cytotoxins

The success of antibody-drug conjugates has demonstrated the value of targeted delivery strategies for cytotoxic molecules. However, many oncogenic drivers remain inaccessible to antibodies due to their intracellular location, and these drivers are currently mainly addressed using small molecule inhibitors. This work explores repurposing such inhibitors for the intracellular delivery and controlled release of cytotoxic payloads. Using click-to-release chemistry, a pre-targeting strategy was developed where inhibitor-tetrazine conjugates enable selective activation of systemically administered trans-cyclooctene (TCO) caged prodrugs. This concept was demonstrated using the epidermal growth factor receptor (EGFR), a key therapeutic target in non-small cell lung cancer. An afatinib-tetrazine conjugate achieved sufficient intracellular retention in EGFR-overexpressing cells to enable toxicity recovery from a TCO-protected monomethyl auristatin E (MMAE) derivative. Successful intracellular targeting and controlled payload release establish a foundation for expanding the scope of targeted drug delivery to previously inaccessible oncogenic drivers.