Screening and Identification of a Novel Anti–Siglec-15 Human Antibody 3F1 and Relevant Antitumor Activity

Abstract

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 (EC 50 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 (EC 50 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 This article has not been copyedited and formatted. The final version may differ from this version.

Recent progress in targeting the sialylated glycan-SIGLEC axis in cancer immunotherapy

“…He et al 106 have developed a monoclonal antibody against SIGLEC15 (3D6), which blocks SIGLEC15-mediated suppression of T cell and moderately prevents tumor growth. Wu et al 107 have conducted monoclonal antibody screening on SIGLEC15 and have found that the 3F1 clone antibody has high receptor blocking activity and significantly reverses the inhibitory effect of SIGLEC15 on lymphocyte proliferation. In mouse experiments, the 3F1 monoclonal antibody has shown significant antitumor efficacy when applied alone or in combination with the Erbitux drug.…”

Dynamic change in Siglec-15 expression in peritumoral macrophages confers an immunosuppressive microenvironment and poor outcome in glioma

“…Recently, Siglec-15, a member of the sialic acid-binding immunoglobulin-type lectins (Siglecs), has emerged as an immune suppressor and a potential target for immunotherapy ( 13 – 15 ). Unlike most other Siglec family members, Siglec-15 is expressed primarily by macrophages and dendritic cells ( 13 , 16 ).…”