Abstract 5528: A highly potent anti-CD39 biparatopic antibody and bispecific for cancer therapy
Authors: Zhang Zhenqing , Jia Yunli , Miao Xiaoniu , Huang Weifeng , Wang Chao , Yuan Zhijun , Jiang Wenchao , Chen Liandi , Li Zhiyuan , Tsun Andy 
Published: June 2022

Abstract
Background: There is an increasing demand for effective combinatory agents to improve upon PD-1/PD-L1-based therapeutics. One combinatory target axis is the adenosine metabolism pathway that consists of three major players, including CD39, CD73 and A2AR. Inhibition of any of these targets have shown enhanced preclinical efficacy in combination with PD-1/PD-L1 inhibitors. CD39 is an ectonucleotidase which degrades extracellular ATP to adenosine monophosphate (AMP). This is considered a rate-limiting step for the further degradation to adenosine by CD73. Adenosine is an immunosuppressive metabolite that can suppress NK and T cells. Blockade of CD39-mediated degradation of ATP to AMP may therefore recover anti-tumor immunity through preventing the enrichment of adenosine in the tumor microenvironment.
Method: Two anti-CD39 VHH molecules were generated, named Ye-37 and Ye-46, which bind to two different epitopes on CD39. Binding experiments were carried out by bio-layer interferometry. Cell binding experiments were tested on CD39-overexpression cell lines by flow cytometry. Cellular CD39 enzymatic inhibition experiments were tested using an MOLP-8 cell line and PBMC via a luminescence-based assay. Soluble CD39 enzymatic tests were carried out on recombinant CD39 protein using a similar method. T cell proliferation assays were performed and observed on CD4+ or CD8+ T cell populations. In vivo efficacy studies were tested in B-NDG B2M-KO mice that were injected subcutaneously with A375-CD39+ tumor cells and human PBMC. An anti-PD1 x CD39 bispecific antibody was then generated by fusing the anti-CD39 biparatopic antibody to the C-terminus of an anti-PD1 IgG and tested using similar methods.
Results: Two candidates, Ye-37 and Ye-46, were selected for their functional activity that recognize non-overlapping epitopes on CD39. The combination of Ye-37 and Ye-46 shows high potency in cell-based and soluble CD39 assays in blocking CD39 activity. Two biparatopic molecules were generated by fusing the biparatopic unit to the N- or C-termini of Fc (46-37-Fc and Fc-37-46) and showed similar activity to the combination. In vivo, we showed single-agent control of tumor growth and potentiation of tumor-growth inhibition when combined with anti-CD73 antibodies. An anti-PD1 x CD39 bispecific was generated and showed potent inhibition of PD-1/PD-L1 interactions by cell-based assays. Potent anti-tumor efficacy was shown, which was as effective as the combination of anti-PD1 plus anti-CD39 antibodies.
Conclusion: Potent anti-CD39 and anti-PD1 x CD39 therapeutic candidates have been generated with promising activity as a combinatory or single agent, respectively. As such, we plan to file for clinical trial authorization of these programs by 2022.
Citation Format: Zhenqing Zhang, Yunli Jia, Xiaoniu Miao, Weifeng Huang, Chao Wang, Zhijun Yuan, Wenchao Jiang, Liandi Chen, Zhiyuan Li, Andy Tsun. A highly potent anti-CD39 biparatopic antibody and bispecific 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 5528.