Abstract 5004: APX005M, a humanized anti-CD40 antibody with strong immune-modulatory activities capable of tumor eradication in vivo

The success of immune checkpoint inhibitors validates the concept that immunotherapy is an effective approach for the treatment of solid tumors. In addition to reversing tumor-induced immune suppression, immune activating antibodies are being explored as the next generation of immuno-oncology therapeutics. CD40, which is expressed on antigen presenting cells such as dendritic and B cells initiates and regulates both innate and adaptive immunity and is essential for the activation of antigen-specific T cells. APX005M is a humanized IgG1 CD40 agonistic antibody developed using Apexigen's APXiMAB™ discovery platform. APX005M binds with high affinity to human (Kd = 0.12nM) and monkey (Kd = 0.37nM) CD40. It recognizes a unique epitope that overlaps with the CD40 ligand binding sites and thus blocks the binding of CD40 to CD40L. APX005M is a potent CD40 agonistic antibody capable of activating antigen presenting B cells (EC50 = 12pM) and dendritic cells (EC50 = 0.49nM). Its CD40 agonistic activity requires crosslinking by Fc-gamma receptors since F(ab)’2 fragment of APX005M loses the agonistic activity. Upon binding to CD40 expressing tumor cells APX005M induces antibody-dependent cellular phagocytosis (ADCP) and apoptosis. In vivo APX005M completely eradicates CD40+ lymphoma tumors and inhibits the growth of rituximab-resistant tumors. The data suggest that a CD40 agonistic mAb such as APX005M, that activates CD40 through binding to the CD40L binding site while being dependent on crosslinking via Fc-gamma receptors, may represent an ideal immune activating antibody drug candidate for stimulating effective immune responses against tumors. APX005M is currently being evaluated in clinical trials for the treatment of patients with solid tumors. Citation Format: Pia Björck, Erin Filbert, Xiaodong Yang, Ovidiu C. Trifan. APX005M, a humanized anti-CD40 antibody with strong immune-modulatory activities capable of tumor eradication in vivo. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5004.