Abstract 5520: AK129, an anti-PD1/LAG-3 bi-specific antibody for cancer therapy

Abstract Background: AK129 is a bi-specific antibody acts by co-blocking two immune checkpoint molecules co-expressed on T cells, PD-1 and LAG-3. Signaling through PD-1/PD-L1 exerts major effects on cytokines production by T cells, inhibiting production of IFN-γ and IL-2. LAG-3 is a cell surface molecule expressed on effector T cells and Tregs, which plays a vital role in regulating T cell function to promote tumoral immune escape. LAG-3 and PD-1 mediate different signaling pathways, but they may act synergistically to cause effector T cell inactivation and exhaustion. AK129 is being investigated as a cancer immunotherapeutic agent. Methods: The antigen binding activity of AK129 to PD-1 and LAG-3 were measured by ELISA and FACS. In reporter gene assay, the bioactivities of AK129 to block the interaction of PD-1 with PD-L1 and to neutralize LAG-3-mediated activity were determined. The bioactivity of AK129 to enhance IL-2 and IFN-γ production in PBMCs via blockade of PD-1 and PD-L1/2 interaction were determined by using cellular assays. In in-vivo pharmacology studies, anti-tumor activity of AK129 was investigated in BALB/c-hPD1/hLAG3 mice bearing CT26.WT tumor model. Results: AK129 showed good antigen binding to PD-1 and LAG-3. AK129 potently inhibited the binding of LAG-3 to its ligand MHC-II, and the binding of PD-1 to its ligand PD-L1, thus blocking downstream immune suppression. At the individual target level, AK129 demonstrated a similar PD-1 blocking activity compared to penpulimab, and similar LAG-3 blocking activity compared to relatlimab. Importantly, at the whole cell level, the enhancement effect of AK129 is stronger than the combination of penpulimab and relatlimab, as evidenced by significantly higher level of IL-2 and IFN-γ secretion from PBMCs. AK129 showed favorable anti-tumor activity in BALB/c-hPD1/hLAG3 mice bearing CT26.WT tumor model, with tumor growth inhibition values reaching 99.27% and 89.48% in high dose (20 mg/kg) and low dose (4 mg/kg) group of AK129, respectively. Conclusion: AK129 is a dual checkpoint blocking bispecific antibody with design features similar to the PD-1/CTLA-4 bispecific antibody AK104, which demonstrated efficacy similar to PD-1 and CTLA-4 antibody combo and much improved safety profile. AK129 has demonstrated robust anti-tumor activity in both in vivo and in vitro pre-clinical studies, and with enhanced T cell activity compared to PD-1 and LAG-3 antibody combo. The efficacy and safety of AK129 await testing in the clinic. Citation Format: Zhaoliang Huang, Xinghua Pang, Tingting Zhong, Chunshan Jin, Na Chen, Dennis Xia, Peng Zhang, Max Wang, Michelle Xia, Baiyong Li. AK129, an anti-PD1/LAG-3 bi-specific antibody for cancer therapy [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 5520.