A PDGFRB- and CD40-targeting bispecific AffiMab induces stroma-targeted immune cell activation

Next-generation CD40 agonists for cancer immunotherapy

INTRODUCTION

There is a need for new therapies that can enhance response rates and broaden the number of cancer indications where immunotherapies provide clinical benefit. CD40 targeting therapies provide an opportunity to meet this need by promoting priming of tumor-specific T cells and reverting the suppressive tumor microenvironment. This is supported by emerging clinical evidence demonstrating the benefits of immunotherapy with CD40 antibodies in combination with standard of care chemotherapy.

AREAS COVERED

This review is focused on the coming wave of next-generation CD40 agonists aiming to improve efficacy and safety, using new approaches and formats beyond monospecific antibodies. Further, the current understanding of the role of different CD40 expressing immune cell populations in the tumor microenvironment is reviewed.

EXPERT OPINION

There are multiple promising next-generation approaches beyond monospecific antibodies targeting CD40 in immuno-oncology. Enhancing efficacy is the most important driver for this development, and approaches that maximize the ability of CD40 to both remodel the tumor microenvironment and boost the anti-tumor T cell response provide great opportunities to benefit cancer patients. Enhanced understanding of the role of different CD40 expressing immune cells in the tumor microenvironment may facilitate more efficient clinical development of these compounds.

Co-culture platform for tuning of cancer receptor density allows for evaluation of bispecific immune cell engagers

Cancer immunotherapy, where a patient's immune system is harnessed to eradicate cancer cells selectively, is a leading strategy for cancer treatment. However, successes with immune checkpoint inhibitors (ICI) are hampered by reported systemic and organ-specific toxicities and by two-thirds of the patients being non-responders or subsequently acquiring resistance to approved ICIs. Hence substantial efforts are invested in discovering novel targeted immunotherapies aimed at reduced side-effects and improved potency. One way is utilizing the dual targeting feature of bispecific antibodies, which have made them increasingly popular for cancer immunotherapy. Easy and predictive screening methods for activation ranking of candidate drugs in tumor contra non-tumor environments are however lacking. Herein, we present a cell-based assay mimicking the tumor microenvironment by co-culturing B cells with engineered human embryonic kidney 293 T cells (HEK293T), presenting a controllable density of platelet-derived growth factor receptor β (PDGFRβ). A target density panel with three different surface protein levels on HEK293T cells was established by genetic constructs carrying regulatory elements limiting RNA translation of PDGFRβ. We employed a bispecific antibody-affibody construct called an AffiMab capable of binding PDGFRβ on cancer cells and CD40 expressed by B cells as a model. Specific activation of CD40-mediated signaling of immune cells was demonstrated with the two highest receptor-expressing cell lines, Level 2/3 and Level 4, while low-to-none in the low-expressing cell lines. The concept of receptor tuning and the presented co-culture protocol may be of general utility for assessing and developing novel bi-specific antibodies for immuno-oncology applications.