TY - JOUR T1 - Screening and Identification of A Novel Anti-Siglec-15 Human Antibody 3F1 and Relevant Antitumor Activity JF - Molecular Pharmacology JO - Mol Pharmacol DO - 10.1124/molpharm.121.000470 SP - MOLPHARM-AR-2021-000470 AU - Jiaguo Wu AU - Jingyi Peng AU - Yangyihua Zhou AU - Ran Zhang AU - Zhihong Wang AU - Naijing Hu AU - Dingmu Zhang AU - Guiqi Quan AU - Yuanyu Wu AU - Jiannan Feng AU - Beifen Shen AU - Jian Zhao AU - Yan Zhang AU - Kaiming Yang AU - Longlong Luo Y1 - 2022/01/01 UR - http://molpharm.aspetjournals.org/content/early/2022/06/28/molpharm.121.000470.abstract N2 - Siglec-15 is an important immunosuppressive molecule considered to be a key target in next generation tumor immunotherapy. In this study, we screened 22 high affinity antibodies that specifically recognize human siglec-15 by using a large human phage antibody library and 5 representative sequences were selected for further study. The results showed the binding activity of 5 antibodies to siglec-15 (EC50 ranged from 0.02368μg /mL to 0.07949 μg /mL) and in 2 siglec-15 overexpressed cell lines, 3 antibodies had the strongest binding activity, so the 2 clones were discarded for further study. Subsequently the affinity of 3 antibodies were measured by Bio-layer interferometry technology (5-9×10E-09M). As the reported ligands of siglec-15, the binding activity of siglec-15 and sialyl-Tn, CD44, MAG and LRRC4C can be blocked by 3 of the antibodies. Among these, 3F1 had a competitive advantage. Then, the antibody 3F1 showed an obvious ADCC effect (EC50 were 0.85 μg/mL). Further, antibody 3F1 can reverse the inhibitory effect of siglec-15 on lymphocyte proliferation (especially CD4+T, CD8+T) and cytokine release (IFN-γ). Given the above results, 3F1 was selected as a candidate for the in vivo pharmacodynamics study. In the tumor model of Balb/c Nude mice, 3F1 (10 mg/kg) showed certain anti-tumor effects (TGI was 31.5%) while the combination of 3F1 (5 mg/kg) and ERBITUX (5 mg/kg) showed significant antitumor effects (TGI was 48.7%) compared with the PBS group. In conclusion, novel human antibody 3F1 has anti-tumor activity and is expected to be an innovative candidate drug targeting siglec-15 for tumor immunotherapy Significance Statement Siglec-15 is considered as an important target in the next generation of tumor immunotherapy. 3F1 is expected to be the most promising potential candidate for targeting siglec-15 for cancer treatment, and could provide a reference for the development of anti-tumor drugs. ER -