An anticancer strategy utilizing DGK ζ inhibitors

Abstract

Upon antigen binding to the T-cell receptor （TCR）, concomitant activation of TCR and CD28 co-stimulatory receptors generates diacylglycerol （DAG） at the plasma membrane. Accumulated DAG activates the downstream PKC and pERK pathways, ultimately triggering cytokine release （e.g., IL-2 and IFN- γ） and inducing T-cell proliferation. Diacylglycerol kinase zeta （DGK ζ ） functions as a negative regulator of this immune response by metabolizing DAG, thereby diminishing T-cell activity. To overcome this immune suppression, we designed and developed PROTAC and ATTEC targeting DGK ζ. Through systematic optimization, compounds 14 and 22a were identified as highly potent PROTAC molecules and ATTEC molecules, exhibiting DC₅₀ values of 27.2 nM and 4 nM, respectively. Notably, both compounds demonstrated safety profiles with negligible human Ether-à-go-go-Related Gene （hERG）-mediated cardiotoxicity and favorable pharmacokinetic stability. In an in vivo MC38 syngeneic xenograft model, compounds 14 and 22a effectively suppressed tumor growth with tumor growth inhibition （TGI） values of 55.73% and 77.36%, respectively. Subsequent mechanistic investigations revealed that the parent DGK ζ inhibitor itself possesses intrinsic degrading activity. Furthermore, this degradation efficacy was fully maintained even when linkers or auxiliary moieties were conjugated to the amine group of the scaffold. Exploiting this unique self-degrading property, we designed a series of dual-acting conjugates by chemically linking the self-degrading DGK ζ inhibitor with a PD-L1 inhibitor, a topoisomerase I inhibitor, and a TLR7 agonist, respectively. These findings provide chance for developing multifunctional synergistic therapeutics in cancer therapy.