Abstract 1846: DuoBody-CD40×4-1BB (GEN1042) induces dendritic-cell maturation and enhances T-cell activation and effector functions in vitro by conditional CD40 and 4-1BB agonist activity

Abstract The clinical success of immune checkpoint inhibitor monoclonal antibodies (mAbs) has demonstrated potential for re-activation of anti-tumor immunity in cancer treatment. DuoBody®-CD40×4-1BB (GEN1042) is a first-in-class bispecific agonistic antibody that combines targeting of costimulatory molecules CD40 and 4-1BB, resulting in priming and (re-)activation of tumor-specific immunity. We previously showed that DuoBody-CD40×4-1BB induces CD40 and 4-1BB agonist activity that is conditional, i.e., dependent on crosslinking of CD40- and 4-1BB-expressing cells. Here we further elucidate the preclinical mechanism of action of DuoBody-CD40×4-1BB in a broad range of functional immune cell assays. Fixed cell microscopy and live cell imaging of the immune synapse was performed using co-cultures of activated T cells and monocyte-derived dendritic cells (DC). DuoBody-CD40×4-1BB co-localized with LFA-1 at the interface between DC and activated T cells. By binding to both targets, DuoBody-CD40×4-1BB enhanced DC/T cell interactions and increased the contact duration between these cells compared to the combination of monovalent CD40- and 4-1BB-specific antibodies. In mixed lymphocyte reactions (MLR) comprised of naïve CD8+ T cells co-cultured with immature (iDC) or LPS-matured monocyte-derived DCs (mDC), DuoBody-CD40×4-1BB induced DC maturation and increased T cell functionality, shown by a dose-dependent increase in HLA-DR/CD86 expression and production of IFNγ, CXCL10 and granzyme B. DC maturation induced by DuoBody-CD40×4-1BB was also observed in monocultures of iDCs expressing both targets, and was associated with a concurrent dose-dependent increase in TNFα production. Furthermore, in antigen-specific T-cell assays (CLDN6-TCR+CD8+ T cells co-cultured with CLDN6+CD40+ DCs), DuoBody-CD40×4-1BB conditionally enhanced T-cell proliferation and production of IFNγ and TNFα, and induced upregulation of the degranulation marker CD107a and granzyme B. Finally, DuoBody-CD40×4-1BB enhanced clonal expansion of human TILs derived from non-small cell lung and colon cancer patients ex vivo in a dose-dependent manner. In conclusion, by enhancing the formation of the immune synapse between CD40+ DC and 4-1BB+ T cells, DuoBody-CD40×4-1BB induced conditional activation of both cell types, resulting in DC maturation, T-cell activation and effector functions in vitro. Thereby, DuoBody-CD40×4-1BB provides a unique combination of priming and enhancing existing anti-tumor immunity. DuoBody-CD40×4-1BB is currently being evaluated in patients with advanced solid tumors in a first-in-human trial (NCT04083599). Citation Format: Alexander Muik, Rachelle Kosoff, Friederike Gieseke, Isil Altintas, Kristina Schödel, Saskia Burm, Eliana Stanganello, Fulvia Vascotto, Aras Toker, Homer Adams, III, Esther Breij, Mustafa Diken, Tahamtan Ahmadi, Kate Sasser, Özlem Türeci, Mark Fereshteh, Ugur Sahin, Maria Jure-Kunkel. DuoBody-CD40×4-1BB (GEN1042) induces dendritic-cell maturation and enhances T-cell activation and effector functions in vitro by conditional CD40 and 4-1BB agonist activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1846.