2O - Penpulimab, an IgG1 anti-PD-1 antibody with Fc-engineering to eliminate effector functions and with unique epitope and binding properties

Background

Currently marketed anti-PD-1 antibodies are typically IgG4 isotype, of which bindings to FcγRs and CH3 region instability might lead to compromise on efficacy and safety. Penpulimab is a humanized IgG1 anti-PD-1 antibody engineered at the Fc region to eliminate binding to FcγRs and C1q, and thus avoid antibody dependent cell-mediated cytotoxicity (ADCC), antibody dependent cellular phagocytosis (ADCP), and complement-dependent cytotoxicity (CDC) to minimize lymphocyte loss, and to avoid antibody dependent cytokine release (ADCR) such as IL-8 and IL-6, which are known to associate with irAEs and poor prognosis in checkpoint blocking immunotherapy.

Methods

Binding kinetics of penpulimab to C1q, FcγRIa, FcγRIIa_H131, FcγRIIa_R131, FcγRIIb, FcγRIIIa_V158 and FcγRIIIa_F158 were measured by Fortebio. ADCC, ADCP and CDC activities were determined in cellular assays. IL-8, IL-6 from macrophage, and IFN-γ and IL-2 from PBMCs were detected by ELISA. Binding kinetics of penpulimab to human PD-1 was determined by Biacore, and epitope/paratope mapping of PD-1/penpulimab was investigated using X-ray crystallography.

Results

Penpulimab exhibited no binding to FcγRIa, FcγRIIa_H131, FcγRIIb, FcγRIIIa_V158, FcγRIIIa_F158 or C1q, and eliciting no apparent ADCC, ADCP or CDC. Additionally, penpulimab induced no remarkable IL-6 and IL-8 release by macrophages in contract to large amount of these cytokines induced by anti-PD-1 antibodies with IgG4 isotype. Unexpectedly, penpulimab is shown in the co-crystal study to bind to human PD-1 N-glycosylation site at N58. This may contribute to a unique slow off-rate of penpulimab binding to PD-1. Thus, penpulimab showed a slower PD-1 binding off-rate (9.51E-05/s) compared to nivolumab (2.43E-04/s) and pembrolizumab (2.80E-04/s). Moreover, penpulimab significantly stimulated IL-2 and IFN-γ secretion in mix lymphocyte reaction, indicating strong T cells activation.

Conclusions

Penpulimab, a PD-1 antibody with IgG1 isotype and Fc engineering, exhibits no Fc receptor mediated effector functions including ADCC, ADCP, and ADCR, and has robust T cell stimulating activity via blocking of PD-1.

Clinical trial identification

Editorial acknowledgement

Tianjing Zheng, Chia Tai Tianqing Pharmaceutical Group Co., Ltd.

Legal entity responsible for the study

Akeso Biopharma Co., Ltd.

Funding

Akeso Biopharma Co., Ltd.

Disclosure

B. Li, Z. Huang, X. Pang, T. Zhong, C. Jin, N. Chen, S. Ma, X. He, D. Xia, X. Jin, Z. Wang, Y. Xia: Financial Interests, Personal, Full or part-time Employment: Akeso Biopharma Co., Ltd.