Abstract 501: APC-loss as a potential biomarker for NT219 treatment in colorectal cancer (CRC)

Background: NT219 is a small molecule dual inhibitor of STAT3 and insulin receptor substrate 1/2 (IRS), covalently binds to IRS1/2 leading to its degradation. IRS regulates PI3K/AKT and the β-catenin pathways. It was demonstrated that NT219 inhibits the IRS2-mediated β-Catenin signaling and synergizes with 5FU to suppress colorectal cancer (CRC) brain metastasis and increase survival. In an APC loss-driven CRC mouse model (CPC-APC), where IGF1R and IRS1/2 are upregulated, the dual inhibitor caused a substantial reduction in tumor burden and metastasis by affecting the tumor and the TME. Here we present the effect of NT219 in CRC patient-derived specimens and suggest upregulation of wnt/β-catenin or loss of its negative regulator APC as a potential biomarker for NT219 therapy. Method: Six CRC ex vivo patient-derived tumor explants (PDEs), involving resected tumor fragments retaining TME native architecture, tumor heterogeneity and proliferative capacity were treated with NT219 and analyzed for efficacy. Genomic and transcriptomic analyses were performed on responding and non-responding biopsies to identify potential predictive biomarkers. Phospo-STAT3(Y705) immunohistochemistry assessed the immediate and sustained effects of NT219. Additional PDEs harboring TP53(D259Y), PIK3CA(E110del) gain-of-function, and APC(s1355fs*60) loss-of-function (LoF), were treated with NT219 w/wo TAS-102. A FOLFOX-resistant patient derived xenograft (PDX) with an APC R1450* LoF mutation received NT219 (60mg/kg, twice weekly) to detect tumor growth. Results: CRC PDEs treated with NT219 showed >75% cell death in 2/6 (33%) samples. Genomic analysis identified APC(E1138fs) LoF mutation (1/2 responders, 0/4 non-responders) and CNV associated with the wnt/ β-catenin pathway (2/2 responders, 0/4 non-responders). Transcriptomic analysis showed differential patterns of genes associated with up-regulation of wnt/β-catenin pathways, such as WNT7A/10A and DDR2. Sustained inhibition of STAT3 phosphorylation was exclusive for responders. Genomic analysis of one biopsy pre vs post- NT219 treatment revealed the APC LoF mutation Y917fs in the pretreatment biopsy which was undetectable post-treatment, suggesting elimination of APC LoF cells. The anti-tumor activity was confirmed in a PDX CRC model harboring APC R1450* in which NT219 demonstrated a single agent sustained tumor growth inhibition (86%, p=0.001). NT219 with TAS-102, induced significant and synergistic cell death (91%) in TAS-102 resistant CRC PDE harboring APC (s1355fs*60) LoF. Conclusion: The anti-tumor activity in CRC explants along with genomic and transcriptomic analysis propose that the response to NT219 is associated with enhanced wnt/β-catenin signaling or APC loss. The results suggest APC-loss as a potential biomarker for NT219 treatment in CRC. Citation Format: Hadas Reuveni, Hava Ben David, Tomer Meirson. APC-loss as a potential biomarker for NT219 treatment in colorectal cancer (CRC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 501.