A canine chimeric monoclonal antibody targeting PD-L1 and its clinical efficacy in canine oral malignant melanoma or undifferentiated sarcoma

Immunotherapy targeting immune checkpoint molecules, programmed cell death 1 (PD-1) and PD-ligand 1 (PD-L1), using therapeutic antibodies has been widely used for some human malignancies in the last 5 years. A costimulatory receptor, PD-1, is expressed on T cells and suppresses effector functions when it binds to its ligand, PD-L1. Aberrant PD-L1 expression is reported in various human cancers and is considered an immune escape mechanism. Antibodies blocking the PD-1/PD-L1 axis induce antitumour responses in patients with malignant melanoma and other cancers. In dogs, no such clinical studies have been performed to date because of the lack of therapeutic antibodies that can be used in dogs. In this study, the immunomodulatory effects of c4G12, a canine-chimerised anti-PD-L1 monoclonal antibody, were evaluated in vitro, demonstrating significantly enhanced cytokine production and proliferation of dog peripheral blood mononuclear cells. A pilot clinical study was performed on seven dogs with oral malignant melanoma (OMM) and two with undifferentiated sarcoma. Objective antitumour responses were observed in one dog with OMM (14.3%, 1/7) and one with undifferentiated sarcoma (50.0%, 1/2) when c4G12 was given at 2 or 5?mg/kg, every 2 weeks. c4G12 could be a safe and effective treatment option for canine cancers

Expression of PD-L1 on canine tumor cells and enhancement of IFN-γ production from tumor-infiltrating cells by PD-L1 blockade.

Programmed death 1 (PD-1), an immunoinhibitory receptor, and programmed death ligand 1 (PD-L1), its ligand, together induce the "exhausted" status in antigen-specific lymphocytes and are thus involved in the immune evasion of tumor cells. In this study, canine PD-1 and PD-L1 were molecularly characterized, and their potential as therapeutic targets for canine tumors was discussed. The canine PD-1 and PD-L1 genes were conserved among canine breeds. Based on the sequence information obtained, the recombinant canine PD-1 and PD-L1 proteins were constructed; they were confirmed to bind each other. Antibovine PD-L1 monoclonal antibody effectively blocked the binding of recombinant PD-1 with PD-L1-expressing cells in a dose-dependent manner. Canine melanoma, mastocytoma, renal cell carcinoma, and other types of tumors examined expressed PD-L1, whereas some did not. Interestingly, anti-PD-L1 antibody treatment enhanced IFN-γ production from tumor-infiltrating cells. These results showed that the canine PD-1/PD-L1 pathway is also associated with T-cell exhaustion in canine tumors and that its blockade with antibody could be a new therapeutic strategy for canine tumors. Further investigations are needed to confirm the ability of anti-PD-L1 antibody to reactivate canine antitumor immunity in vivo, and its therapeutic potential has to be further discussed

Red dichromatic imaging improves visibility of bleeding during gastric endoscopic submucosal dissection

Abstract Bleeding frequently occurs during gastric endoscopic submucosal dissection (ESD) and bleeding points are sometimes difficult to detect. Red dichromatic imaging (RDI) was recently developed to improve the visibility of bleeding. Our study aimed at examining the efficacy of RDI in improving the visibility of bleeding during gastric ESD. We retrospectively evaluated the visibility score and color difference of bleeding spot during gastric ESD during September 2020–January 2021. The visibility score was evaluated as four numeric values by operators, and the color difference between the bleeding spot and surroundings was evaluated using RDI and white light imaging (WLI). A further analysis to evaluate bleeding characteristics was performed to evaluate the possible beneficial effects of RDI. Twenty patients with a total of 85 bleedings were analyzed. The mean visibility score in RDI was significantly higher than that in WLI (3.69 ± 0.60 vs 3.20 ± 0.84, p < 0.01). The color difference with RDI was also significantly higher than that with WLI (19.51 ± 15.18 vs 14.80 ± 7.41, p < 0.01). Furthermore, in the bleedings with a higher visibility score in RDI, the color difference in RDI was significantly higher than that in WLI (23.99 ± 19.29 vs 14.33 ± 7.08, p < 0.01). The multivariate analysis of visibility scores revealed that submergence of bleeding points was independently associated with the superiority of RDI (odds ratio 10.35, 95% confidence interval: 2.76–38.81, p < 0.01). Our study demonstrates that RDI can improve the visibility of bleeding during gastric ESD

Expressions of PD-L1 on dog tumor cell lines.

<p>The expression of PD-L1 was evaluated by flow cytometric analysis using anti-PD-L1 mAb 4G12-C1. -; <3% positive, +; 3–30% positive, ++; 30–60% positive, +++; >60% positive.</p><p>*Cells were incubated with recombinant canine IFN-γ (100 ng/ml) for 24 h before the analysis.</p