Abstract B124: MYTX-011 is a highly internalized ADC with anti-tumor activity across a spectrum of NSCLC preclinical models with various levels of cMET expression
Authors: Comb William C , Kanojia Deepak , Colombo Federico , Ramesh Vijay , Gera Nimish , Chittenden Thomas , Fiske Brian 
Published: December 2023

Abstract
cMET overexpression occurs in non-small cell lung cancer (NSCLC) and antibody-drug conjugates targeting cMET (cMET-ADCs) have been developed to treat cMET+ NSCLC tumors irrespective of dependency on cMET signaling. cMET-ADCs have shown promising clinical activity, but largely in a subset of NSCLC patients whose tumors express the highest cMET levels. MYTX-011, an investigational, pH-sensitive ADC incorporating the clinically validated vcMMAE linker-payload, was specifically designed to potentially benefit a broader population of patients including those whose tumors express lower cMET levels. We’ve previously demonstrated that pH-sensitive cMET binding of MYTX-011 drives higher internalization in cMET+ tumor cells, and greater cytotoxicity against a panel of cMET+ cancer cell lines in vitro. MYTX-011 also shows superior efficacy in NSCLC xenograft models with high or moderate cMET expression levels when compared to the matched non-pH-sensitive Parent ADC or a Benchmark ADC generated by hinge conjugation of a clinical stage anti-cMET ADC antibody to vcMMAE. Here we demonstrate that the MYTX-011 monoclonal antibody, which is engineered to selectively and rapidly lose affinity at the acidic pH of endolysosomes, rapidly internalizes and accumulates in cells expressing moderate cMET levels compared to the matched parent antibody. MYTX-011 in vitro cytotoxicity correlated with cMET expression levels and conferred sensitivity to cells that were otherwise insensitive to ADCs generated with the parent or Benchmark antibodies. Importantly, cells that were only sensitive to MYTX-011, but not matched controls, expressed low and moderate levels of cMET. Furthermore, MYTX-011 was active against the low cMET-expressing NCI-H2122 xenograft model in vivo whereas the Benchmark ADC was inactive. In the moderate cMET-expressing NCI-H1975 xenograft model, MYTX-011 was more active than both the Benchmark ADC and a second benchmark ADC generated by hinge conjugation of a clinical stage biparatopic anti-cMET ADC antibody to a maytansinoid linker/toxin. MYTX-011 activity was further evaluated against a panel of NSCLC patient derived xenograft (PDX) models with relevant histology, cMET expression, and genetic profiles. MYTX-011 was highly active in cMET+ squamous and adenocarcinoma PDX, EGFR WT and mutant PDX, in a PDX model with MET ex14 skipping mutation, and in PDX with heterogenous cMET expression. Together, these findings highlight the potential of MYTX-011 as a therapeutic candidate for treating a broader range of cMET+ NSCLC malignancies than other cMET-ADCs.
Citation Format: William C Comb, Deepak Kanojia, Federico Colombo, Vijay Ramesh, Nimish Gera, Thomas Chittenden, Brian Fiske. MYTX-011 is a highly internalized ADC with anti-tumor activity across a spectrum of NSCLC preclinical models with various levels of cMET expression [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr B124.