Abstract Background: The limited efficacy of current hepatocellular carcinoma (HCC) treatments drives the need for novel molecular targets. Building on our previous discovery that LANCL1 promotes HCC tumor initiation by reducing cellular reactive oxygen species (ROS), this study aims to validate it as a druggable target and develop a first-in-class humanized antibody therapeutic. Methods: We generated a parental murine monoclonal antibody (mAb) against LANCL1. Its efficacy was evaluated in vitro using sphere-formation, cytotoxicity, migration, and invasion assays on HCC cell lines, and in vivo in an orthotopic HCC model. For clinical translation, we created humanized variants, with binding affinity assessed by Surface Plasmon Resonance (SPR). Results: In vitro, the parental murine mAb potently inhibited cancer stemness (90% reduction in sphere formation), induced significant cytotoxicity (55% viability), and suppressed migration and invasion (67.6% and 85.3%, respectively). In vivo, it impaired tumor growth by 50.3%. This efficacy was demonstrated in an orthotopic NOD SCID model established with implanted human hepatic tumor cells. We next evaluated nine humanized variants, finding that all exhibited binding affinity comparable to the parental antibody. Specifically, Variant 1 showed strong inhibition at 62.8%, an efficacy close to the chimeric antibody (83.5%). Although Variant 2 was less potent, it still achieved significant inhibition at 44.5%. This confirms the humanization process successfully retained anti-tumor efficacy. Conclusion: This work is novel as it presents the first therapeutic antibody targeting LANCL1. Our findings not only confirm the therapeutic potential of LANCL1 inhibition but also demonstrate the potent anti-tumor activity of a novel humanized antibody, providing a strong foundation for future clinical development. Citation Format: Chui-Yee Diana O, Yu-Man Tsui, Irene Oi-Lin Ng, . Targeting LANCL1 with a humanized monoclonal antibody suppresses tumorigenesis in hepatocellular carcinoma 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 1643.
O et al. (Fri,) studied this question.