A novel nanobody-based agonist-redirected checkpoint (ARC) molecule, aPD1-Fc-OX40L, for cancer immunotherapy - Immune checkpoint inhibitors (ICIs) have shown unprecedented clinical activity in a wide range of malignancies. However, their efficacy remains limited in many malignancies due to primary or acquired resistance. Targeted therapies that activate tumor necrosis factor receptor superfamily (TNFRSF) members, like OX40 & 4-1BB, are currently explored to augment the clinical efficacy of ICIs. In this study, we have constructed a novel-nanobody (Nb) based Agonist-Redirected Checkpoint (ARC) platform that consolidates immune checkpoint blockade (ICB) and TNFRSF agonism in a single biologic. Our long-term goal is to utilize this Nb-based ARC platform to develop novel immunotherapeutics to treat canine and human cancer patients. The objective of this R15 proposal is to investigate the impact of our first Nb-based ARC molecule, aPD1-Fc-OX40L, on local and systemic antitumor immune response in pet dogs with oral malignant melanoma (OM). aPD1-Fc-OX40L utilizes an anti-PD1 nanobody to disrupt the PD1/PD-L1 axis and the extracellular domain (ECD) of the OX40 ligand to activate the OX40 pathway. Our preliminary data show that aPD1-Fc-OX40L folds properly binds to cognate receptors with high affinity, activates the OX40 pathway, and blocks canine PD-L1 binding to PD1. Our specific aims will: (Aim 1) assess the safety and pharmacokinetic (PK) profile of aPD1-Fc-OX40L; (Aim 2) conduct a phase II/III clinical trial of aPD1-Fc-OX40L in canine patients with oral melanoma (OM); and (Aim 3) assess the functional activities of aPD1-Fc-OX40L over monotherapies. We will perform clinical correlative studies (using flow cytometry and immunohistochemistry (IHC)) on tumor and peripheral blood samples collected before and after administration of aPD1-Fc-OX40L to understand the cellular and molecular mechanisms that determine the antitumor immune response. Upon conclusion, we will gain valuable insights into the safety, PK profile, and clinical efficacy of aPD1-Fc-OX40L. This contribution is significant since this will be the first study to evaluate concomitant PD1 blockade and OX40 agonism in a highly relevant large animal model of human mucosal melanoma. The data gathered from this study will create a blueprint to employ a similar therapeutic strategy to treat human cancer patients. The proposed research is innovative because we have developed a highly flexible Nb-based ARC platform that can be easily adapted to engineer novel immunotherapeutic combinations targeting other immune checkpoints and TNFRSF receptors. The availability of these species-specific immunotherapeutics will allow the integration of canine patients with spontaneous tumors into immune-oncology research, which will benefit both humans and pet dogs. It will provide dogs with access to cutting-edge cancer treatments while ensuring that people are given treatments that are more likely to succeed.
