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855 Diacylglycerol kinase alpha and zeta dual inhibitors enhance T cell responses and promote robust and durable anti-tumor T cell immunity
  1. Marcos Steinberg,
  2. Darina Spasova,
  3. Danelle Eto,
  4. AnneMarie Pferdekamper,
  5. Phuong Nguyen,
  6. Brian Le,
  7. Zachary Naiman,
  8. Susan Murphy,
  9. Maricel Gozo,
  10. James Skipper,
  11. Taylor Ismaili,
  12. Xikui Liu,
  13. Sunil Sahdeo,
  14. Xiao Hu,
  15. Isharat Yusuf,
  16. Kristen Taylor Meadows and
  17. Laura Carter
  1. Gossamer Bio, Inc., San Diego, CA, United States


Background Diacylglycerol kinases (DGK) convert diacylglycerol (DAG) into phosphatidic acid which limits DAG-induced propagation of T cell activation.1 T cells predominantly express DGK alpha and DGK zeta isoforms (DGKalpha/zeta),2 and deletion of either enhances T cell activation and function.3,4 DGKalpha/zeta are overexpressed in tumor infiltrating T cells and may limit the anti-tumor activity of these cells.5 Thus, inhibition of DGKalpha/zeta is a potential therapeutic avenue to enhance T cell anti-tumor responses. We demonstrate that inhibition of DGKalpha/zeta with novel dual DGKalpha/zeta inhibitors (DGKi) enhances anti-tumor T cell activity.

Methods The role of DGKalpha/zeta in T cell activation was studied using wildtype and CRISPR-knockout T cells. In vitro studies assessing the effect of DGKi were conducted using various mouse and human T cell functional assays. T cell exhaustion studies were performed in T cells from lymphocytic choriomeningitis virus (LCMV) clone 13-infected mice. In vivo activity of DGKi was assessed by measuring T cell activation in OT-I mice challenged with OVA-peptides. Efficacy studies and memory rechallenge experiments were performed in the MC38 syngeneic tumor model.

Results CRISPR knockout studies characterizing the role of DGKalpha/zeta on T cells demonstrated that both isoforms regulate T cell activation and function. DGKi enhanced IFN gamma production by human melanoma-specific T cells stimulated with the weak affinity MART1 antigen. Similarly, treatment of mouse OT-I cells with DGKi enhanced responses to low-affinity OVA-peptides and OT-I-mediated cytotoxicity of MC38-OVA tumor cells. Treatment of exhausted CD8 T cells with DGKi reverted exhaustion caused by chronic LCMV infection, and enhanced T cell function with PDL1 blockade. DGKi rescued cytokine release from T cells suppressed by adenosine, TGF beta or PGE2 treatment. Oral administration of DGKi resulted in dose-dependent increase in T cell activation in mice. Furthermore, DGKi in combination with anti-PD-1 therapy was efficacious in the MC38 model with complete tumor regressions in treated animals. These mice eradicated tumors upon rechallenge with MC38 cells two months later, demonstrating durable anti-tumor memory responses.

Conclusions We demonstrate that DGKalpha/zeta negatively regulates T cell activity. Dual DGKalpha/zeta inhibition restores T cell responses to weak tumor antigens, overcomes cell exhaustion, and enhances CD8 T cell cytotoxic activity. In vivo efficacy data demonstrates that DGKi in combination with anti-PD-1 antibody therapy promotes robust anti-tumor responses and generates durable T cell memory. These data support dual DGKalpha/zeta inhibition in combination with anti-PD-1 antibodies as a therapeutic approach for cancer treatment.


  1. Mérida I, Avila-Flores A, Merino E. Diacylglycerol kinases: at the hub of cell signalling. Biochem J. 2008; 409(1):1–18.

  2. Krishna S, Zhong X. Role of diacylglycerol kinases in T cell development and function. Crit Rev Immunol. 2013; 33(2):97–118.

  3. Guo R, Wan C-K, Carpenter JH, et al. Synergistic control of T cell development and tumor suppression by diacylglycerol kinase alpha and zeta. Proc Natl Acad Sci U S A. 2008; 105(33):11909–14.

  4. Riese MJ, Grewal J, Das J, et al. Decreased diacylglycerol metabolism enhances ERK activation and augments CD8+ T cell functional responses. J Biol Chem. 2011; 286(7):5254–65.

  5. Prinz PU, Mendler AN, Masouris I, et al. High DGK-α and disabled MAPK pathways cause dysfunction of human tumor-infiltrating CD8+ T cells that is reversible by pharmacologic intervention. J Immunol. 2012; 188(12):5990–6000.

Ethics Approval All animal studies were approved and conducted in accordance with the Explora IACUC Program of Veterinary Care.

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