Abstract Background: Constitutive activation of NRF2, driven by NFE2L2 gain-of-function or KEAP1 or CUL3 loss-of-function mutations, disrupts KEAP1-CUL3-mediated NRF2 degradation and contributes to resistance to chemotherapy, immunotherapy, and targeted therapies, including RAS inhibitors. This oncogenic pathway is frequently altered in squamous cell carcinomas — such as esophageal (ESCC) and lung squamous cell carcinoma (LUSC) — via NFE2L2 hotspot mutations in the DLG/ETGE motifs. In lung adenocarcinoma (LUAD), KEAP1 mutations are common and often co-occur with KRAS mutations. Although KEAP1/NFE2L2 mutations are relatively uncommon in pancreatic ductal adenocarcinoma, more than half of tumors exhibit pronounced nuclear NRF2 accumulation, likely driven by activation of the RAS pathway. Despite the clinical relevance of this pathway, no approved therapies directly target KEAP1/NRF2-mutant tumors. Methods: GFH603 was developed as a molecular glue-like allosteric activator of KEAP1 to restore KEAP1-CUL3 E3 ligase function. Its ability to promote KEAP1-CUL3 complex formation, induce NRF2 degradation, and suppress proliferation of NRF2-driven cancer cells was evaluated in vitro. In vivo anti-tumor efficacy was assessed using xenograft models. Combination studies with pan-RAS inhibitors were conducted in KRAS/KEAP1 co-mutant cell lines. ADMET profiling was performed to assess drug-like properties. Results: GFH603 enhanced KEAP1-CUL3 complex assembly and promoted NRF2 degradation. In vitro, it induced NRF2 degradation in NFE2L2 W24C-mutant KYSE70 cells ( IC50 = 1.7 nM) and inhibited proliferation of NFE2L2-amplified HCC95 cells (IC50 = 3.6 nM). In the HCC95 xenograft model, GFH603 (5 mg/kg once daily) achieved significant tumor growth inhibition (TGI = 114%) and robust NRF2 degradation in tumor tissues. In the LU6407 NFE2L2-mutant patient-derived xenograft model, GFH603 (10 mg/kg once daily) demonstrated strong tumor regression as a single agent, indicating its potential as an effective monotherapy. Furthermore, GFH603 demonstrated synergistic anti-proliferative activity when combined with pan-RAS inhibitors in KRAS/KEAP1 co-mutant cell lines. ADMET profiling revealed favorable characteristics, including high oral bioavailability, low hERG liability, and negative Ames test results. Conclusions: GFH603 restores KEAP1-CUL3 E3 ligase activity through a molecular glue mechanism, enabling targeted degradation of NRF2 in KEAP1/NFE2L2-mutant tumors. It demonstrates potent efficacy as monotherapy in NRF2-activated squamous cancer models (e.g., ESCC, LUSC) and synergizes with pan-RAS inhibitors in KRAS/KEAP1 co-mutant cells. These findings support GFH603 as a promising therapeutic candidate for overcoming NRF2-driven resistance and addressing a critical unmet need in oncology. Further preclinical and clinical development are warranted. Citation Format: Xiang Yu, Tao Jiang, Tao Liang, Feng Yan, Li Wang, Jingyang Zhang, Siyuan Le, Fusheng Zhou, Jiong Lan, Qiang Lu. GFH603: A molecular glue-like allosteric activator of the KEAP1-CUL3 E3 ligase complex for targeting NRF2-activated tumors 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 348.
Yu et al. (Fri,) studied this question.