XFab-α4-1BB/CD40L fusion protein activates dendritic cells, improves expansion of antigen-specific T cells, and exhibits antitumour efficacy in multiple solid tumour models

• Published in: Cancer Immunology, Immunotherapy Immunotherapy, 2023-12, Vol.72 (12), p.4015-4030
• Main Authors: Wang, Bochun, Liu, Yujie, Yuan, Ruofei, Dou, Xiaoqian, Qian, Niliang, Pan, Xiujie, Xu, Guili, Xu, Qinzhi, Dong, Bo, Yang, Cuima, Li, Hongjie, Wang, Jingjing, Bai, Guijun, Liu, Liangfa, Gao, Xin
• Format: Article
• Language: English
• Subjects: Animal models; Animals; Antibodies; Antigens; Bispecific antibodies; Cancer Research; CD40 antigen; CD40 Antigens; CD40 Ligand; CD40L protein; Cell activation; Cell fusion; Cell proliferation; Dendritic Cells; Fusion protein; Gemcitabine; Humans; Immune checkpoint inhibitors; Immunology; Immunotherapy; Infiltration; Lymphocytes; Lymphocytes T; Medicine; Medicine & Public Health; Metastases; Mice; Neoplasms - metabolism; Neoplasms - therapy; Oncology; Pharmacodynamics; Primates - metabolism; Solid tumors; T-Lymphocytes - metabolism; Toxicity; Trimers; Tumors; Vaccination
• ISSN: 0340-7004; 1432-0851; 1432-0851
• DOI: 10.1007/s00262-023-03535-y

Background Additional immunotherapies are still warranted for non-responders to checkpoint inhibitors with refractory or relapsing cancers, especially for patients with “cold” tumours lacking significant immune infiltration at treatment onset. We developed XFab-α4-1BB/CD40L, a bispecific antibody targeting 4-1BB and CD40 for dendritic cell activation and priming of tumour-reactive T cells to inhibit tumours. Methods XFab-α4-1BB/CD40L was developed by engineering an anti-4-1BB Fab arm into a CD40L trimer based on XFab® platform. Characterisation of the bispecific antibody was performed by cell-based reporter assays, maturation of dendritic cell assays, and mixed lymphocyte reactions. The abilities of antigen-specific T-cell expansion and antitumour efficacy were assessed in syngeneic mouse tumour models. Toxicological and pharmacodynamic profiles were investigated in non-human primates. Results XFab-α4-1BB/CD40L demonstrated independent CD40 agonistic activity and conditional 4-1BB activity mediated by CD40 crosslinking, leading to dendritic cell maturation and T-cell proliferation in vitro. We confirmed the expansion of antigen-specific T cells in the vaccination model and potent tumour regression induced by the bispecific antibody alone or in combination with gemcitabine in vivo, concomitant with improved tumour-reactive T-cell infiltration. XFab-α4-1BB/CD40L showed no signs of liver toxicity at doses up to 51 mg/kg in a repeated-dose regimen in non-human primates. Conclusions XFab-α4-1BB/CD40L is capable of enhancing antitumour immunity by modulating dendritic cell and T-cell functions via targeting 4-1BB agonism to areas of CD40 expression. The focused, potent, and safe immune response induced by the bispecific antibody supports further clinical investigations for the treatment of solid tumours.