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1066 Pharmacologic inhibition of DGKα activates T cells and enhances anti-tumor immunity
  1. Adele Wang,
  2. Lance Stapleton,
  3. Jean-Philippe Belzie,
  4. Weimei Xing,
  5. Gladys Muiru,
  6. Dmytro Kornyeyev,
  7. Edward Hsieh,
  8. Albert Liclican,
  9. Pamela Toy,
  10. Mengshu Xu,
  11. Kei Kim,
  12. Jacob Lee,
  13. Michelle Kuhne and
  14. Latesh Lad
  1. Gilead Sciences, Inc., Foster City, CA, USA


Background Immunotherapies blocking checkpoint receptors on T cells have demonstrated impressive activity in cancer patients, however, a significant population of patients do not respond to these therapies or develop acquired resistance over time. Therefore, alternate approaches to enhance T cell immunity are needed to broaden and deepen the current clinical response rates in patients. A potential promising approach is to target intracellular negative regulators of T cell receptor (TCR) signaling. Diacylglycerol (DAG) is a key second messenger that links TCR signal strength to the intensity and duration of signaling by the RAS-extracellular signal-regulated kinase (ERK)- and protein kinase C (PKC)-dependent pathways. Diacylglycerol kinase α (DGKα) is an intracellular lipid kinase that is enriched in T cells and functions as a key negative regulator of TCR signaling by catalyzing the conversion of DAG to phosphatidic acid (PA), thus attenuating DAG-mediated signaling. Inhibition of DGKα maintains levels of DAG following TCR stimulation and potentiates T cell activation. Here we describe a potential first-in-class, potent, highly selective and orally bioavailable inhibitor of DGKα.

Methods The proximal activity and specificity of Gilead’s inhibitor for enhancing the main TCR-driven transcriptional nodes was measured in Jurkat cell lines containing a luciferase reporter under the control of NFAT, NF-kB, or AP-1. To assess anti-tumor activity of the inhibitor in vitro, a three-dimensional GFP-expressing human breast tumor spheroid co-culture assay with CD8+ T cells was established. Tumor lysis was determined by assessing the reduction of GFP signal and supernatants were collected to measure IFN-γ and granzyme B production. In parallel, to further confirm the activation of T cells by the inhibitor, splenocytes from OT-I mice were stimulated and supernatants were collected for IL-2 quantification. Furthermore, Gilead’s inhibitor was evaluated in multiple mouse tumor models to assess anti-tumor efficacy as monotherapy and in combination with checkpoint antibodies.

Results Gilead’s DGKα inhibitor enhanced DAG-mediated TCR signaling pathways (AP-1 and NF-kB), leading to augmented T cell activation, as measured by increased IL-2, IFN-γ and granzyme B secretion, that resulted in increased T cell-dependent killing of tumor cells in vitro. In colorectal (CT26 and MC38) and melanoma (B16F10) mouse tumor models, the inhibitor demonstrated tumor growth inhibition as a monotherapy and improved the efficacy of α-PD-1 and α-CTLA-4.

Conclusions Specific inhibition of DGKα by Gilead’s inhibitor enhances effector T cell function, leading to robust tumor growth inhibition in mouse tumor models as a monotherapy and potentiating the activity of checkpoint blockade.

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