EGFR and LGR5 Dual-Targeting Antibody-Drug Conjugate-Based Therapeutic Strategies for the Improved Treatment of Colorectal Cancer

Peyton High, BS (Advisor: Kendra Carmon, PhD)

Despite significant efforts, colorectal cancer (CRC) prognosis remains poor, exemplifying a need for improved therapies. Antibody-drug conjugates (ADCs) are a rapidly expanding class of therapeutics that utilize antibody-mediated specificity for a target antigen overexpressed on the tumor surface to deliver highly potent drug payloads to cancer cells while sparing normal tissues. Here, we describe the development of a novel topoisomerase I inhibitor-conjugated ADC (8E11-CPT2) targeting leucine-rich repeat-containing G protein-coupled receptor 5 (LGR5), a marker of cancer stem-like cells highly overexpressed in CRC, that elicits dose- and target-dependent cytotoxicity with minimal toxicity. Furthermore, we demonstrate that cetuximab (CTX), a mAb targeting the epidermal growth factor receptor (EGFR) that is FDA-approved for KRAS^WT mCRC, increases LGR5 levels independent of KRAS mutation. Importantly, combination treatment of CTX and 8E11-CPT2 significantly reduces tumor burden and extends survival in RAS^MUT CRC patient-derived xenografts as compared to monotherapies. Having validated EGFR and LGR5 dual therapeutic targeting as an effective strategy, we then generated two EGFR:LGR5 bispecific antibodies (bsAbs; E?L-1 and E?L-2) that drive EGFR lysosomal degradation in an LGR5-driven manner. Furthermore, we produced an EGFR:LGR5 bsADC (E?L-1-CPT2) that demonstrates significantly enhanced cytotoxicity in EGFR- and LGR5-expressing cancer cell lines and superior anti-tumor efficacy in CRC xenografts as compared to E?L-1 bsAb and 8E11-CPT2 LGR5 ADC. Taken together, this work strongly rationalizes dual-targeting of EGFR and LGR5 for CRC and is in line with growing evidence that multi-targeting therapeutic strategies may prove more effective in treating cancer than single target-based approaches.

• Advisory Committee:
  Kendra Carmon, PhD, Chair
• Ali Azhdarinia, PhD
• Rachel Miller, PhD
• Vihang Narkar, PhD
• Jae-ll Park, PhD
• Kyle Poulsen, PhD

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