Abstract 3789: INCB177054: A novel, potent, orally bioavailable DGKα/ζ dual inhibitor enhances T-cell function and demonstrates potent antitumor activity

Abstract Host immune responses play an important role in fighting cancers; therefore, improving these responses against tumor cells is of high interest in cancer therapy. Diacylglycerol (DAG) is a key second messenger that transduces T-cell receptor (TCR) activation signal to downstream effectors through DAG-binding proteins. DAG kinase (DGK) isoforms α and ζ are the major enzymes that modulate DAG levels in T cells and serve as intracellular checkpoints to attenuate TCR activation. Here, we describe INCB177054, a novel, potent, selective, and orally bioavailable small molecule DGKα/ζ dual inhibitor that enhances T-cell activation in vitro and in vivo and demonstrates antitumor activity in mouse tumor models. Consistent with the DGKα and DGKζ biology in regulating DAG levels in T cells, our genetic data and pharmacological inhibition studies in Jurkat T cells indicated that optimal T-cell activation requires inhibition of both DGKα and DGKζ activity. In biochemical ADP-Glo assays, INCB177054 demonstrated potent inhibition of DGKα and DGKζ with subnanomolar half-maximal inhibitory concentration and >500-fold selectivity over other DGK isoforms, such as DGKβ, DGKγ, and DGKδ. Mechanism-based biochemical studies suggest a noncompetitive mode of inhibition vs both ATP and DAG substrates. In cellular assays, INCB177054 enhanced both ERK and NFκB phosphorylation, expression of early T-cell activation marker CD69, and production of cytokines, such as IL-2 and IFNγ. In vitro, INCB177054 treatment enhanced T-cell responses to weak antigens and enhanced both allogenic T cell- and NK cell-mediated killing in coculture assays. In vivo, INCB177054 induced T-cell activation upon antigen stimulation in an OT-1 mouse model. INCB177054 monotherapy induced modest tumor growth inhibition in MC38 and CT26 syngeneic mouse models. However, when combined with PD-1 checkpoint inhibition, INCB177054 showed significant tumor growth inhibition in both models, ultimately leading to tumor rejection in most of the mice. In addition, those mice were protected against a rechallenge with the same tumor, suggesting generation of antitumor T-cell memory. Collectively, our data indicate INCB177054 is a potent and selective DGKα/ζ dual inhibitor that enhances T-cell activity and induces significant tumor growth inhibition when combined with anti-PD(L)-1, suggesting this potential therapy might increase responses to checkpoint inhibitor treatment in patients with cancer. Citation Format: Xiaodi Ren, Yvonne Lo, Michelle Pusey, Lisa Truong, Michelle Frascella, Rodrigo Hess, Kelly Federowicz, Joshua Hummel, Bo Wei, Gengjie Yang, Maryanne Covington, Chen Bao, Guofeng Zhang, Melissa Chan, Yu Li, Jennifer Rocha, Rina Pan, Anthony Perry, Sarah Li, Jinyuan (Jay) Zhang, Brad Yuska, David Rodrigues, Xiaozhao Wang, Jeff Jackson, Patrick Mayes, Sunkyu Kim. INCB177054: A novel, potent, orally bioavailable DGKα/ζ dual inhibitor enhances T-cell function and demonstrates potent antitumor activity [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 3789.