Dual targeting of RANKL and PD-1 with a bispecific antibody improves anti-tumor immunity.

William C Dougall,Amelia Roman Aguilera,Mark J Smyth

doi:10.1002/cti2.1081

Abstract

ObjectivesThe addition of RANKL/RANK blockade to immune checkpoint inhibitors (ICIs) such as anti‐PD‐1/PD‐L1 and anti‐CTLA4 antibodies is associated with increased anti‐tumor immunity in mice. Recent retrospective clinical studies in patients with advanced melanoma and lung cancer suggest the addition of anti‐RANKL antibody to ICI increases the overall response rate relative to ICI treatment alone. Based on this rationale, we developed a novel bispecific antibody (BsAb) co‐targeting RANKL and PD‐1.MethodsWe characterized target binding and functional activity of the anti‐RANKL/PD‐1 BsAb in cell‐based assays. Anti‐tumor activity was confirmed in experimental lung metastasis models and in mice with established subcutaneously transplanted tumors.ResultsThe anti‐RANKL/PD‐1 BsAb retained binding to both RANKL and PD‐1 and blocked the interaction with respective counter‐structures RANK and PD‐L1. The inhibitory effect of anti‐RANKL/PD‐1 BsAb was confirmed by demonstrating a complete block of RANKL‐dependent osteoclast formation. Monotherapy activity of anti‐RANKL/PD‐1 BsAb was observed in anti‐PD‐1 resistant tumors and, when combined with anti‐CTLA‐4 mAb, increased anti‐tumor responses. An equivalent or superior anti‐tumor response was observed with the anti‐RANKL/PD‐1 BsAb compared with the combination of parental anti‐RANKL plus anti‐PD‐1 antibodies depending upon the tumor model.DiscussionMechanistically, the anti‐tumor activity of anti‐RANKL/PD‐1 BsAb required CD8+T cells, host PD‐1 and IFNγ. Targeting RANKL and PD‐1 simultaneously within the tumor microenvironment (TME) improved anti‐tumor efficacy compared with combination of two separate mAbs.ConclusionIn summary, the bispecific anti‐RANKL/PD‐1 antibody demonstrates potent tumor growth inhibition in settings of ICI resistance and represents a novel modality for clinical development in advanced cancer.

Highlights

Immunotherapies that target immune checkpoint receptors (e.g. PD-1 or CTLA-4) on T cells or PD-L1 present on tumor and host myeloid cells have shown great advances in the treatment of certain advanced solid organ malignancies.[1]
We demonstrated that blockade of RANKL with anti-RANKL mAb (IK22/5) improved anti-metastatic and anti-tumor activity achieved with antibodies targeting PD-1/PD-L1 in mouse models of melanoma and prostate cancer (Ahern15)
We report that the concurrent neutralisation of RANKL and PD-1 by a bispecific antibody (BsAb) consistently demonstrated superior anti-tumor or anti-metastatic control to monotherapies, even in 2019 | Vol 8 | e1081 Page 8

Summary

Introduction

Immunotherapies that target immune checkpoint receptors (e.g. PD-1 or CTLA-4) on T cells or PD-L1 present on tumor and host myeloid cells have shown great advances in the treatment of certain advanced solid organ malignancies.[1]. RANK (TNFRSF11a) and RANKL (TNFSF11) are members of the tumor necrosis factor receptor and ligand superfamilies, respectively, with closest homology to CD40 and CD40L.6 This pathway is currently best known for a role in bone homeostasis, as the differentiation of osteoclasts requires RANKL interaction with RANK expressed on the myeloid osteoclast precursors.[7] The anti-RANKL antibody (denosumab) blocks RANKL-RANK interactions resulting in antagonism of RANK signalling and is widely used in clinical practice as an anti-resorptive, bone protective agent in patients with bone metastasis or postmenopausal osteoporosis.[7] despite this clinical focus, the RANKL/RANK pathway was initially described in terms of dendritic cell (DC)– T-cell biology and RANK signalling in myeloid cells has more recently been recognised to have tolerogenic effects in different contexts[8,9,10,11] suggesting potential applications of RANKL/RANK antagonism beyond the current, skeletally targeted supportive care applications and, instead, as an anti-cancer therapy, via immune activation

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