Exploiting intracellular oncogenic proteins to release cytotoxins

Area of Science:

• Oncology
• Medicinal Chemistry
• Molecular Biology

Background:

• Antibody-drug conjugates highlight targeted cytotoxic delivery, but many oncogenic drivers are intracellular and inaccessible to antibodies.
• Small molecule inhibitors are currently used for intracellular targets but lack targeted delivery mechanisms.
• Developing novel strategies for targeted intracellular delivery of cytotoxic payloads is crucial for advancing cancer therapy.

Purpose of the Study:

• To explore repurposing small molecule inhibitors for intracellular delivery and controlled release of cytotoxic payloads.
• To develop a pre-targeting strategy using click-to-release chemistry for selective activation of caged prodrugs.
• To demonstrate the feasibility of this approach using an epidermal growth factor receptor (EGFR) targeted therapy.

Main Methods:

• Utilized click-to-release chemistry to create inhibitor-tetrazine conjugates for targeted activation.
• Developed systemically administered *trans*-cyclooctene (TCO) caged prodrugs for controlled payload release.
• Employed an afatinib-tetrazine conjugate to target EGFR-overexpressing cells and deliver a monomethyl auristatin E (MMAE) payload.

Main Results:

• Achieved sufficient intracellular retention of the afatinib-tetrazine conjugate in EGFR-overexpressing cells.
• Demonstrated successful toxicity recovery from a TCO-protected MMAE derivative upon intracellular activation.
• Validated the concept of targeted intracellular delivery and controlled release of cytotoxic payloads.

Conclusions:

• Repurposing small molecule inhibitors with click-to-release chemistry enables targeted intracellular delivery of cytotoxic payloads.
• This strategy allows for controlled payload release, overcoming limitations of traditional antibody-drug conjugates for intracellular targets.
• Establishes a foundation for expanding targeted drug delivery to previously inaccessible oncogenic drivers, improving cancer treatment efficacy.