Title : Advancing EGFR-targeting macrocyclic peptide-drug conjugates to target KRAS-mutant solid tumors: Design, synthesis, and preclinical evaluations
Abstract:
Background: Epidermal Growth Factor Receptor (EGFR) is a well-validated oncological marker overexpressed in colorectal (CRC) and pancreatic (PC) cancers. However, conventional therapies like Cetuximab fail completely in patients possessing downstream KRAS mutations, which autonomously drive tumor survival. Moving away from traditional signaling blockade toward receptor-mediated endocytosis offers a powerful paradigm shift to bypass mutation-driven drug resistance.
Objective: To develop and evaluate modular Peptide-Drug Conjugates (PDCs) utilizing an EGFR-homing macrocyclic peptide to selectively deposit diverse cytotoxic payloads directly into resistant solid tumors.
Methods: The macrocyclic peptide P6; c(CHVPGSYIC)-which binds a unique, non-canonical allosteric extracellular site on EGFR to trigger rapid internalization, was used as the targeting carrier. P6 was conjugated to two distinct payload classes using solid-phase and solution-phase platforms: a first-generation construct bearing Topoisomerase I inhibitor SN38 via a cleavable ester linker, and a second-generation construct anchoring ultra-potent dolastatin-10 analogue DA1 shielded by a metabolically rigid urea linkage. Both PDCs were systematically evaluated for serum stability, selective cell uptake, and in vivo efficacy across KRAS-mutant HCT116 (CRC) and PANC1 (PC) mouse xenograft models.
Results: The cleavable P6-SN38 conjugate successfully bypassed KRAS resistance in vivo, achieving robust tumor growth suppression in HCT116 models through targeted DNA damage without systemic toxicity. Expanding the platform to target microtubule dynamics, the second-generation, non-cleavable urea-linked P6-DA1 conjugate demonstrated excellent sustained stability in biological fluids. When evaluated head-to-head against the clinical combination standard-of-care (Cetuximab + Irinotecan), the ultra-potent second-generation construct induced profound, sustained tumor regression across both hyper-aggressive HCT116 and PANC-1 xenograft models.
Conclusion: Non-canonical EGFR targeting using the P6 macrocycle is a highly effective delivery strategy. Transitioning to advanced urea-shielded DA1 architectures provides the exceptional metabolic stability and low-nanomolar potency required to eradicate "untargetable" KRAS-mutant solid tumors.
