Highly Potent Immunotoxins Targeting the Membrane-distal N-lobe of GPC3 for Immunotherapy of Hepatocellular Carcinoma

Jingwen Li; Lanxin Xiang; Qian Wang; Xuqian Ma; Xin Chen; Yuankui Zhu; Yaxi Yang; Le Huang; Huixia He; Lilei Xu; Xinjun Liang; Shuang Dong; Sheng Hu; Hanjie Li; Mingqian Feng

doi:10.7150/jca.66978

Highly Potent Immunotoxins Targeting the Membrane-distal N-lobe of GPC3 for Immunotherapy of Hepatocellular Carcinoma

J Cancer. 2022 Feb 14;13(4):1370-1384. doi: 10.7150/jca.66978. eCollection 2022.

Authors

Jingwen Li¹, Lanxin Xiang¹, Qian Wang¹, Xuqian Ma¹, Xin Chen¹, Yuankui Zhu¹, Yaxi Yang¹, Le Huang¹, Huixia He¹, Lilei Xu², Xinjun Liang³, Shuang Dong³, Sheng Hu³, Hanjie Li⁴, Mingqian Feng⁵

Affiliations

¹ College of Life Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, China.
² Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, No. 30 Shuangqing Road, Beijing 100084, China.
³ Department of Internal Medicine-Oncology, Hubei Cancer Hospital, Wuhan, Hubei 430070, China.
⁴ CAS Key Laboratory of Quantitative Engineering Biology, Shenzhen Institute of Synthetic Biology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong 518055, China.
⁵ College of Biomedicine and Health, Huazhong Agricultural University, Wuhan, Hubei 430070, China.

Abstract

Glypican-3 (GPC3) has become a compelling target for immunotherapy of hepatocellular carcinoma, including antibody-drug conjugate (ADC), and ADC-like immunotoxin. To investigate the impact of epitopes on the potency of ADCs, current study generated a large panel of chicken monoclonal antibodies (mAbs) that targeted 12 different and over-lapping epitopes on GPC3. These mAbs demonstrated a very high affinity with K_d values in the range of 10^-9-10^-14 M, and the highest affinity (K_d value of 0.0214 pM) was 40-fold higher than the previously generated high-affinity mAb YP7 (K_d value of 0.876 nM). Additionally, these mAbs exhibited excellent thermostability with T_m values in the range of 45-82 °C. As a proof-of-concept study for ADC, we made immunotoxins (scFv fused with PE24, the 24-kDa cytotoxic domain of Pseudomonas exotoxin A) based on these mAbs, and we found that immunotoxins targeting the N-lobe of GPC3 were overall much more potent than those targeting the C-lobe and other locations. One representative N-lobe-targeting immunotoxin J80A-PE24 demonstrated 3 to 13-fold more potency than the hitherto best immunotoxin HN3-PE24 that was previously developed. J80A-PE24 could suppress tumor growth much greater than HN3-PE24 in a xenograft mouse model. Combination of J80A-PE24 with an angiogenesis inhibitor FGF401 showed additive effect, which dramatically shrank tumor growth. Our work demonstrated that, due to high affinity, excellent thermostability and potency, chicken mAbs targeting the N-lobe of GPC3 are appealing candidates to develop potent ADCs for immunotherapy of liver cancer.

Keywords: GPC3; epitope mapping; hepatocellular carcinoma; immunotoxin; monoclonal antibody.