Abstract 4214: LIGHT (TNFSF14) costimulation with TIGIT blockade broadens the activity of checkpoint inhibitors (CPIs) into CPI refractory and resistant tumors through targeted myeloid cell and effector lymphocyte activation
Authors: Yoo Kyung Jin , Gonzalez Louis , Johannes Kellsey , Miriyala Jayalakshmi , Lenz Karen , Campbell Kristen , de Silva Suresh , Schreiber Taylor H. , Fromm George J. 
Published: June 2022

Abstract
Although increased TIGIT expression on TILs is associated with poor survival in patients with cancer, monotherapy TIGIT antibody blockade has not yet demonstrated significant clinical activity. PD-1 is commonly co-expressed on TILs, and PD-1 mediated SHP-2 signaling inhibits DNAM-1 (CD226), preventing PVR co-stimulation in the setting of TIGIT blockade. The interaction between PD-1 and CD226 explains why TIGIT blockade only translates to clinical benefit in the setting of co-blockade of PD-1/L1, however does not explain why co-blockade of TIGIT and PD-1/L1 does not provide benefit in advanced and PD-1/L1 resistant tumors. In advanced and PD-1/L1 resistant tumors, progressive downregulation of CD226 has been reported. Thus, we hypothesized that the lack of CD226 may underlie the lack of clinical responses to combined TIGIT/PD-1/L1 blockade in PD-1/L1 experienced tumors and we sought to identify alternative costimulatory receptors with high-expression. Analysis of TCGA, as well as single-cell RNASeq from TILs, identified HVEM and LTβR as two costimulatory receptors with higher expression in advanced cancers as compared to CD226. HVEM and LTβR directly activate CD8+ T, natural killer (NK), and myeloid cells when bound by their TNF superfamily ligand, known as LIGHT. LIGHT potentiates effector lymphocyte function through signaling that obviates the co-stimulatory role of DNAM-1. We demonstrated that when the extracellular domain (ECD) of LIGHT is combined with the ECD of TIGIT on a TIGIT-Fc-LIGHT bi-functional fusion protein, the simultaneous blockade of PVR, PVRL2, PVRL3, and Nectin-4 and immune co-stimulation by LIGHT increased CD8+ T and NK infiltration into tumors. This translated into tumor cell killing, regression of established tumors, and improved survival in preclinical models of checkpoint primary and acquired resistance. The translation of TIGIT-Fc-LIGHT activity was evaluated in cynomolgus macaques and was well tolerated at doses up to 40 mg/kg. A series of adaptive immune and proinflammatory cytokines, including IL-2, CCL2, CCL4, IL-10, CXCL10, and CCL17, were induced within two hours of TIGIT-Fc-LIGHT infusion. Additionally, receptor engagement led to the rapid margination of HVEM+CD8+ T cells from the periphery into secondary immune tissues. This network of cytokines and post-dose immune cell margination identified in the monkey, was identical to findings in murine models that ultimately translated into significant anti-tumor responses. Lastly, the combination of TIGIT-Fc-LIGHT with anti-PD(L)1 broadened anti-tumor activity of the checkpoint antibodies in aggressive CPI-resistant tumors. These results suggest that LIGHT could be the differentiator that extends the clinical activity of conventional CPIs into PD-L1 low or CPI acquired resistance tumors.
Citation Format: Kyung Jin Yoo, Louis Gonzalez, Kellsey Johannes, Jayalakshmi Miriyala, Karen Lenz, Kristen Campbell, Suresh de Silva, Taylor H. Schreiber, George J. Fromm. LIGHT (TNFSF14) costimulation with TIGIT blockade broadens the activity of checkpoint inhibitors (CPIs) into CPI refractory and resistant tumors through targeted myeloid cell and effector lymphocyte activation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4214.