Bispecific Antibody-Bound T Cells as a Novel Anticancer Immunotherapy

Discovery and functional characterization of canine PD-L1-targeted antibodies for evaluating antitumor efficacy in a canine osteosarcoma xenograft model

Targeting the programmed cell death protein 1 (PD-1)/programmed death ligand 1 (PD-L1) pathway is promising in treating cancer in humans and offers potential for veterinary applications. However, no PD-L1 antibodies have been approved specifically for treating canine cancer. We aimed to develop PD-L1-specific antibodies using phage display technology for treating canine cancer. A synthetic antibody library was screened, and 18 high-affinity single-chain variable fragment clones were subsequently converted to the IgG format for enhancing binding affinity and functional stability. The clone #15 exhibited the highest binding affinity and most pronounced antitumor effects. The PD-1/PD-L1 interaction was inhibited by antibody #15. The binding and thermal stabilities of the antibodies were validated by flow cytometry and thermal stability assays, respectively. In NOG mice xenografted with canine osteosarcoma cells and treated with canine peripheral blood mononuclear cells and antibody #15, the tumor size and weight were reduced. Antibody #15 significantly increased apoptosis of tumor cells and lymphocyte populations. Therefore, anti-PD-L1 antibodies, particularly antibody #15, have substantial potential as novel immunotherapeutic agents against canine osteosarcoma. This study represents a significant advancement in veterinary oncology, with the potential of improving treatment outcomes for canine cancers and providing insights into similar strategies in human cancer therapy.

The expression of PD-L1 on tumor-derived exosomes enhances infiltration and anti-tumor activity of αCD3 × αPD-L1 bispecific antibody-armed T cells

Anti-cluster of differentiation (CD) 3 × α programmed death-ligand 1 (PD-L1) bispecific T-cell engager (BsTE)-bound T-cells (BsTE:T) are a promising new cancer treatment agent. However, the mechanisms of action of bispecific antibody-armed activated T-cells are poorly understood. Therefore, this study aimed to investigate the anti-tumor mechanism and efficacy of BsTE:T. The BsTE:T migration was assessed in vivo and in vitro using syngeneic and xenogeneic tumor models, flow cytometry, immunofluorescence staining, transwell migration assays, microfluidic chips, Exo View R100, western blotting, and clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 technology. In murine B16 melanoma, MC38 colon cancer, and human multiple myeloma cells, BsTE:T exhibited superior tumor elimination relative to that of T-cells or BsTE alone. Moreover, BsTE:T migration into tumors was significantly enhanced owing to the presence of PD-L1 in tumor cells and secretion of PD-L1-containing exosomes. Furthermore, increased infiltration of CD44highCD62Llow effector memory CD8+ T-cells into tumors was closely associated with the anti-tumor effect of BsTE:T. Therefore, BsTE:T is an innovative potential anti-tumor therapy, and exosomal PD-L1 plays a crucial role both in vitro and in vivo in the anti-tumor activity of BsTE:T.

Enhancing anti-CD274 (PD-L1) targeting through combinatorial immunotherapy with bispecific antibodies and fusion proteins: from preclinical to phase II clinical trials

INTRODUCTION

Immune checkpoint inhibitors have achieved great success in the treatment of many different types of cancer. Programmed cell death protein ligand 1 (PD-L1, CD274) is a major immunosuppressive immune checkpoint and a target for several already approved monoclonal antibodies. Despite this, novel strategies are under development, as the overall response remains low.

AREAS COVERED

In this review, an overview of the current biomarkers for response to PD-L1 inhibitor treatment is given, followed by a discussion of potential novel biomarkers, including tumor mutational burden and circulating tumor DNA. Combinatorial immunotherapy is a potential novel strategy to increase the response to PD-L1 inhibitor treatment and currently, several interesting bispecific antibodies as well as bispecific fusion proteins are undergoing early clinical investigation. We focus on substances targeting PD-L1 and a secondary target, and a secondary immunomodulatory target like CTLA-4, TIGIT, or CD47.

EXPERT OPINION

Overall, the presented studies show anti-tumor activity of these combinatorial immunotherapeutic approaches. However, still relatively low response rates suggest a need for better biomarkers.