Abstract 5657: HK010, a novel anti-PDL1 × CD137 bispecific antibody, exhibits potent anti-tumor immunity and low toxicity
Authors: Li Liangwei , Liu Wenting , Shen Guodong , Zhang Dayan , Zhou Weiming , Wang Fengrong , Zeng Xiaoli , Huang Yang , Cheng Liansheng 
Published: April 2023

Abstract
Background: Checkpoint inhibitors targeting the PD-1/PD-L1 have changed the treatment and prognosis for patients with advanced solid tumors. There remains a unmet need for additional therapies due to treatment resistance. Tumor-necrosis superfamily members, such as CD137 and CD40, have been shown to synergize with the checkpoint inhibitors in preclinical studies. However, agonists antibodies have exhibited limited clinical activity for severe liver toxicity. Here we have developed a Fc-silenced bispecific antibody targeting PD-L1 and CD137, HK010, which could overcome these limitations by tumor-directed T-cell activation and checkpoint blockade.
Methods: The antigen binding specificity and affinity of HK010 were determined by enzyme-linked immunosorbent assay (ELISA), surface plasmon resonance (SPR) and flow cytometry. The functional activity of HK010 was determined using in vitro cell-based assays and reporter gene assay. Transgenic mice expressing human PD-L1 and 4-1BB were transplanted with human PD-L1-expressing murine MC38 cells to assess in vivo antitumor activity. Cytokine release assay was conducted by incubating HK010 with peripheral blood mononuclear cells (PBMCs) from healthy donors (n=6). The pharmacokinetic (PK) behavior and safety profiles of HK010 were characterized in cynomolgus monkeys.
Results: HK010 is a IgG4 PD-L1 × 4-1BB bsAb, which was designed to maintain a high affinity for human PD-L1 and a low affinity for human 4-1BB (KD PD-L1: 2.27 nM; KD 4-1BB: 493 nM) to achieve strong blocking of PD-1/PD-L1 and appropriate agonism of 4-1BB. HK010 retained full blockade activity on PD-1/PD-L1 signaling and enhances T-cell proliferation and IFN-γ production in vitro primary cell assays and Mixed lymphoid reaction (MLR). In addition, it led to a dose-dependent increase in the CD137-driven NFκB reporter gene activation through the bridging of PD-L1 on target cells and CD137 on effector cells. In humanized PD-L1/4-1BB transgenic mice bearing with MC38/hPDL1 tumor, HK010 showed robust single agent anti-tumor activity and induced durable antigen-specific immunological memory that prevents the growth of the same tumor cells in the mice re-challenged. There were no signs of toxicity in human cytokine release assay for HK010. Toxicology data in cynomolgus monkeys showed that HK010 was well-tolerated up to 150 mg/kg (MTD≥150mg/kg) dose without systemic toxicity. Furthermore, HK010 was confirmed to be highly safe in the 5-week repeated-dose toxicity study with no observed treatment-related mortality, abnormality in hematological indexes, important organs.
Conclusion: These data demonstrate that HK010, an anti-PD-L1 × CD137 bispecific antibody, may exert a strong localized anti-tumor therapeutic efficacy with a low risk of liver toxicity through tumor-directed T-cell activation and checkpoint blockade in tumors.
Citation Format: Liangwei Li, Wenting Liu, Guodong Shen, Dayan Zhang, Weiming Zhou, Fengrong Wang, Xiaoli Zeng, Yang Huang, Liansheng Cheng. HK010, a novel anti-PDL1 × CD137 bispecific antibody, exhibits potent anti-tumor immunity and low toxicity. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5657.