Abstract C064: Combination of D3L-002, an anti-TIGIT/PVRIG bispecific antibody, with D3S-001, a KRAS G12C inhibitor, transformed tumor microenvironment from “cold” to “hot” and achieved durable tumor remission in preclinical models
Authors: Chen George , Zhang Jing , Rui Haopeng , Yang Xiaofeng , Wang Tienan 
Published: December 2023

Abstract
KRAS G12C inhibitors have demonstrated encouraging clinical benefit in patients with solid tumors harboring KRAS G12C mutation. However, the overall response rate and duration of response remain to be improved. Though combining KRAS G12C inhibitors with anti-PD-1 antibodies showed enhanced preclinical efficacy, clinical benefit for this regimen was compromised by treatment-related toxicities. While the mechanisms underlining these toxicities are being actively investigated, combination strategies incorporating other immunotherapies into KRAS G12C inhibition may provide an alternative to anti-PD-1 combination. We have discovered a new bispecific antibody (BsAb), D3L-002, targeting the TIGIT and PVRIG immune checkpoint molecules that are expressed on activated T and NK cells and mediate inhibitory signaling to counteract the immune stimulatory DNAM-1 pathway. To assess the combination effect of D3L-002 with KRAS G12C inhibitors, the anti-tumor efficacies of KRAS G12C inhibitor D3S-001, a murine surrogate anti-TIGITxPVRIG BsAb (mTxP BsAb), a murine anti-PD-1 antibody (mPD-1 Ab), the combination of D3S-001 with mTxP BsAb and with mPD-1 Ab were evaluated in CT-26 KRAS G12C syngeneic mouse tumor models. Tumor microenvironment (TME) profiling was analyzed by flow cytometry, immunohistology and single cell sequencing. In this study, D3S-001 monotherapy inhibited tumor growth with a 50% complete remission (CR) rate. While mTxP BsAb alone was not effective in this immune “cold” model, combination of D3S-001 with mTxP BsAb resulted in a 70% CR rate, comparable to that of the combination of D3S-001 with the mPD-1 Ab. TME profiling indicated that D3S-001 remodeled the TME from “cold” to “hot” by reducing M2 macrophages and MDSCs while increasing T cells in the tumor. Interestingly, D3S-001 treatment led to increased expression of DNAM-1 on T cells, which has been implicated in augmenting T cell sensitivity towards environmental stimulation. The expression of TIGIT and PD-1 was also upregulated on T cells after D3S-001 treatment, correlating with enhanced T cell activation and anti-tumor efficacy in the combination group of mTxP BsAb and D3S-001 or mPD-1 Ab and D3S-001, respectively. In single cell analysis, mTxP BsAb demonstrated a distinctive effect in regulating immune suppressive Treg population from that of the mPD-1 Ab. While Treg population was increased in D3S-001 or the combination of D3S-001 with mPD-1 Ab group, it was decreased in mTxP BsAb monotherapy or D3S-001 and mTxP BsAb combination group. Collectively, these data showed that D3S-L002’s surrogate mTxP BsAb synergized with D3S-001 in achieving enhanced and durable anti-tumor effect in KRAS G12C-mutant tumors. The combination treatment transformed TME from “cold” to “hot” and inhibited Treg population. These results provide a strong rationale for combining D3L-002 with D3S-001 in clinic trials, which may lead to an alternative treatment option, with differentiated mechanisms and potentially better tolerability, from current strategy in combining anti-PD-1 antibodies with KRAS G12C inhibitors.
Citation Format: George Chen, Jing Zhang, Haopeng Rui, Xiaofeng Yang, Tienan Wang. Combination of D3L-002, an anti-TIGIT/PVRIG bispecific antibody, with D3S-001, a KRAS G12C inhibitor, transformed tumor microenvironment from “cold” to “hot” and achieved durable tumor remission in preclinical models [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr C064.