Therapeutic co-targeting of LGR5 and MET to overcome heterogeneity and therapy resistance in colorectal tumors

ABSTRACT:
Tumor heterogeneity and therapy resistance remain challenges to the successful treatment of metastatic
colorectal cancer (mCRC). Leucine-rich repeat containing G protein-coupled receptor 5 (LGR5) is upregulated
in a large fraction of primary colorectal tumors and metastases with low expression in normal tissues. LGR5 has
also been validated as a marker of cancer stem-like cells (CSCs) that self-renew and drive tumor growth and
metastasis. We and others generated LGR5-targeted antibody-drug conjugates (ADCs) incorporating
microtubule inhibitors to target CSCs and eliminate colorectal tumors. However, these first-generation LGR5
ADCs only led to tumor inhibition, followed by relapse once treatment was terminated, due in part to LGR5
downregulation and drug payload selection. Interestingly, we showed loss of LGR5 mediated by LGR5-targeted
ADCs or genetic knockout in CRC cells resulted in activation of the receptor tyrosine kinase MET to enhance
survival and therapy resistance of LGR5-negative CRC cells. MET is also highly expressed in primary colorectal
tumors and metastases with lower expression in normal tissues and MET-targeted ADCs have shown great
promise in clinical trials for different tumor types. Therefore, we hypothesize co-targeting LGR5 and MET with
ADCs, incorporating two different drug payloads with different mechanisms of action, will overcome tumor
heterogeneity and therapy resistance attributed to target downregulation and/or payload insensitivity. Recently,
we utilized a site-specific conjugation approach to generate new LGR5- and MET-targeted ADCs with diverse
payloads that are more potent in CRC models. Thus, we propose in Aim 1 to first scale-up production and
characterize LGR5- and MET-targeted ADCs. The ADCs will then be tested as monotherapies and in
combination to measure effects on tumor antigen binding, internalization, signaling pathways, and cytotoxicity in
a panel of CRC cell lines and patient-derived tumor organoids that express different levels of LGR5 and MET. In
Aim 2, ADCs will be evaluated as monotherapies and in combination for safety and toxicity studies in normal
immunocompetent mice and therapeutic efficacy in patient-derived xenograft models of CRC. This project could
have significant impact for the treatment of mCRC and lead to future studies toward the development of a novel
LGR5/MET ADC combination to overcome tumor heterogeneity and therapy resistance to eliminate tumors and
prevent relapse.

Grant Number: 1R21CA302991-01
NIH Institute/Center: NIH
Principal Investigator: Kendra Carmon