Preclinical development of a novel bispecific mAb-Trap fusion protein, IMM2520, targeting both PD-L1 and CD47 as cancer immunotherapy

Abstract The programmed cell death protein 1 (PD-1) immune checkpoint is well known in its ability to attenuate T cell-mediated immune responses in tumors expressing its ligand, programmed death-ligand 1 (PD-L1). CD47, a cell surface molecule in the immunoglobulin superfamily, is another established target overexpressed on various malignant cells and acts as an innate inhibitory checkpoint by interrupting the phagocytosis of tumor cells and downstream activation of innate responses. It has been reported that the simultaneous blockade on both CD47 and PD-L1 checkpoints inhibited tumor growth and circulating tumor cells metastasis more potently than a single antibody inhibition or blank control in the 4T1 tumor mouse model in vivo. IMM2520 is an antibody-receptor (mAb-Trap) fusion protein consisting of recombinant human SIRPα and anti- PD-L1 antibody, thereby targeting CD47 and PD-L1 to antagonize both innate and adaptive immune checkpoint pathways. IMM2520 binds to PD-L1 on the tumor cell membrane and restores the immune response of T cells. IMM2520 also reverses the inhibitory effect of tumor cells on macrophages by blocking the binding of CD47 on the tumor cell to SIRPα on macrophages. In vitro studies have demonstrated that IMM2520 not only possesses a potent binding activity to CD47 (EC50 = 0.8 nM) and PD-L1 (EC50 = 0.09 nM) respectively, but also exhibits a strong activity in blocking PD-1/PD-L1 binding (IC50 = 0.06 - 1.0 nM). IMM2520 also showed a potent antibody-dependent cellular cytotoxicity (ADCC, EC50 = 1.54 ng/ml) against Raji-PDL1 and induced a strong antibody-dependent cellular phagocytosis (ADCP, EC50 = 0.04 nM) activity (THP-1 against Raji-PDL1). In vivo efficacy study with CT26-hPD-L1/hCD47 colon cancer model demonstrated that IMM2520 at 3 mg/kg significantly reduced tumor volume (TGITV = 90.12%, P<0.01 vs Vehicle). Interestingly, IMM2520 demonstrated a potent and significantly higher anti-tumor activities than IMM01 (a SIRPα-Fc fusion protein) and IMM2505 (also a CD47XPD-L1 mAb-Trap, but the variable region sequence of this PD-L1 antibody is identical to atezolizumab). IMM2520 at dose of 6 mg/kg completely eradicated the established tumors. In another in vivo efficacy study with MC38-hCD47/hPD-L1 colon cancer model, IMM2520 demonstrated a significant anti-tumor activity in a dose-dependent manner at doses between 2 mg/kg to 20 mg/kg. Given its potent preclinical anti-tumor activity as well as the favorable safety profile, IMM2520 may serve as a potent immunotherapy for multiple cancer types by targeting PD-L1 and CD47 on tumor cells. Citation Format: Wenzhi Tian, Song Li, Dianze Chen, Wenqi Zhu, Yanan Yang, Dandan Liu, Huiqin Guo, Chunmei Yang, Li Zhang, Wei Zhang, Xiaoping Tu, Liang Peng, Gui Zhao, Ruliang Zhang, Fan Zhang, Frank Gan. Preclinical development of a novel bispecific mAb-Trap fusion protein, IMM2520, targeting both PD-L1 and CD47 as cancer immunotherapy [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 1878.