Abstract 1858: FAK inhibition by APG-2449 enhances the antitumor activity of MAPK pathway blockade in <i>BRAF</i> V600E-mutant tumor models.

Abstract Background: BRAF mutations are present in approximately 4% to 8% of all cancers, predominantly in colorectal cancer (CRC), melanoma, and non-small-cell lung cancer. Among them, the V600E mutation is the most common and functionally activating form, leading to constitutive activation of the mitogen-activated protein kinase (MAPK) signaling cascade. Combined BRAF and MEK inhibition has shown substantial clinical benefit in BRAF V600E-mutant melanoma and CRC. However, resistance frequently develops through feedback reactivation of ERK or compensatory activation of the PI3K-AKT signaling pathway. Recent evidence indicates that focal adhesion kinase (FAK) signaling is also adaptively reactivated upon MAPK inhibition, contributing to therapeutic resistance. This study evaluated the effects of APG-2449, a potent and selective multikinase (FAK) inhibitor, on the antitumor activity of BRAF inhibitor dabrafenib and MEK inhibitor trametinib in BRAF V600E-mutant CRC and melanoma preclinical models. Methods: Cell proliferation was measured by CellTiter-Glo® assay or clonal formation assay. Apoptosis was assessed using flow cytometry. Protein expression levels were examined by western blot. Antitumor effects of APG-2449, alone or combined with dabrafenib and trametinib, were evaluated in C32 and RKO xenograft models in vivo. Results: Cell proliferation assays across a panel of human cancer cell lines revealed that cell lines harboring BRAF V600E were more sensitive to APG-2449 than those without MAPK pathway alterations. APG-2449 synergistically enhanced the antiproliferative efficacy of dabrafenib and trametinib in both BRAF inhibitor-sensitive (C32 and Colo205) and -insensitive (RKO and LS411N) cells. The triple combination (APG-2449 + dabrafenib + trametinib) caused synergistic growth inhibition in C32 and RKO cells compared with BRAF/MEK dual blockade. Mechanistically, APG-2449 attenuated feedback reactivation of ERK signaling and bypass activation of the PI3K-AKT pathway induced by BRAF/MEK inhibition, resulting in sustained suppression of p-ERK and p-AKT expression, prolonged cell growth inhibition, and enhanced cell apoptosis. In in vivo studies, the triple combination (T/C: 4.55% for C32; 17.18% for RKO) outperformed APG-2449 alone (T/C: 106.09% for C32; 96.93% for RKO) or dabrafenib + trametinib (T/C: 35.39% for C32; 78.45% for RKO) in tumor growth inhibition. APG-2449 synergistically enhanced the antitumor activity of trametinib + dabrafenib in C32 and RKO xenograft models, with synergy ratios of 8.25 and 4.43, respectively. Conclusions: APG-2449 suppresses compensatory signaling activation induced by MAPK pathway blockade and synergistically enhances the antitumor activity of dabrafenib + trametinib. These results warrant clinical development of APG-2449 for patients with melanoma or CRC harboring BRAF V600E. Citation Format: Zhou Yu, Zhiyan Liang, Xinyi Yao, Shujie He, Dajun Yang, Yifan Zhai. FAK inhibition by APG-2449 enhances the antitumor activity of MAPK pathway blockade in BRAF V600E-mutant tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 1858.