Abstract 4482: Catalytic inhibition of NSD2 demonstrates <i>in vitro</i> antitumor activity in head and neck squamous cell carcinoma.

Abstract NSD2 is a histone methyltransferase that catalyzes H3K36 dimethylation and is frequently altered or overexpressed in diverse cancers. Recent work has demonstrated that selective NSD2 catalytic inhibitors suppress tumor growth in preclinical models of pancreatic and lung cancer by reprogramming chromatin and transcriptional states. However, the effect of NSD2 catalytic inhibition in other solid and hematologic malignancies remains undefined. Prior studies from our lab and others demonstrated that NSD2 depletion suppresses HNSCC cell growth. We therefore evaluated the activity of a highly selective NSD2 inhibitor (IACS-17817) and its enantiomer (IACS-17818) as a negative control in head and neck squamous cell carcinoma (HNSCC) JHU-11 and FaDu cell lines, as well as in the RPMI-8402 acute lymphoblastic leukemia (ALL) cell line, which carries an NSD2-activating mutation. Cells were treated with escalating concentrations of the inhibitor for 72 hours, and cells were treated with a fixed concentration of the compounds at serial time points. Then, global H3K36me2 levels were tested via western blotting. IACS-17817 decreased H3K36me2 levels in a time and concentration-dependent manner, with a significant drop at treatment concentrations as low as 10 nM of the active compound after 72 hours in all cell lines tested. IACS-17817 showed an onset of action as early as 24 hours in HNSCC and 48 hours in ALL cells. NSD2 inhibition suppressed the proliferation of HNSCC cells as measured by clonogenic assays in a time- and concentration-dependent manner. ALL RPMI-8402 methylcellulose cell survival is also being evaluated, and results are pending. Combination treatment with IACS-17817 and the PARP inhibitor olaparib demonstrated additive cytotoxicity compared to single agents in HNSCC cells, as shown in clonogenic assays. These findings broaden the known therapeutic scope of NSD2 catalytic inhibition from pancreatic and lung cancers to head and neck squamous cell carcinoma (HNSCC), highlighting NSD2 as a convergent oncogenic driver and supporting further preclinical development of NSD2-targeting agents for clinical translation. Citation Format: Amr Ismail, Iuliia Topchu, Tingting Zhang, Ahmed Ismail, Peter Makhov, Jia Xu, Kang Le, Michael Soth, Yanis Boumber. Catalytic inhibition of NSD2 demonstrates in vitro antitumor activity in head and neck squamous cell 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 4482.