Abstract 3180: Development of a fully automated immunoassay system for detection of serum NY-ESO-1 and XAGE1 antibodies as biomarkers predicting the clinical efficacy of anti-PD-1 therapy
Authors: Sakai Yumiko , Abo Hirotaka , Sakaeda Kanako , Atarashi Yusuke , Ide Nobuyuki , Yamaoka Takaaki , Kurose Koji , Noda Kenta , Sato Toshiyuki , Oga Toru , Oka Mikio 
Published: September 2020

Abstract
Background: Programmed cell death-1 (PD-1) and PD-ligand1 (PD-L1) inhibitors have become standard therapies for advanced non-small-cell lung cancer (NSCLC) due to prolonged patient survival. However, extended survival with anti-PD-1/PD-L1 therapy is limited to a small subset of NSCLC patients. Therefore, predictive biomarkers are needed to determine which patients will benefit. Recently, we reported that serum antibodies (Abs) against NY-ESO-1 and/or XAGE1 cancer-testis antigens are useful biomarkers that predict the clinical efficacy of anti-PD-1 monotherapy for NSCLC. The serum Abs were measured with enzyme-linked immunosorbent assay (ELISA); however, the ELISA method has several technical limitations for clinical applications. To overcome limitations in Ab measurement, we have developed a fully automated immunoassay system (HISCLTM) using chemiluminescent magnetic immunoassay technology. HISCLTM is widely used in many clinical fields because it is superior to ELISA due to its rapid reaction (17 minutes), wide dynamic ranges, and high reproducibility.
Patients and Methods: Sera of NSCLC patients were obtained before anti-PD-1 monotherapy (nivolumab or pembrolizumab) as a part of standard care. NY-ESO-1/XAGE1 serum Abs were measured by ELISA and HISCLTM and their clinical performance was evaluated. In HISCLTM system, serum Abs were captured by magnetic beads coated with antigens, and the antigen-Ab complex was incubated with anti-human IgG conjugated with alkaline phosphatase. The chemiluminescent intensity acquired was then used for analyses.
Results: Twenty-eight NSCLC patients were selected as the initial cohort for this study. Half of the patients responded to anti-PD-1 monotherapy and the remaining half did not. There were strong correlations between HISCLTM chemiluminescence signal intensity and titers of NY-ESO-1 and XAGE1 serum Abs in ELISA (r&gt;0.93 for both). Twelve of thirteen Ab-positive patients in HISCLTM responded to anti-PD-1 therapy, while only two of fifteen Ab-negatives did (92% vs. 13%, p&lt;0.001). Notably, the signal intensities in HISCLTM correlated well with tumor reduction rates after anti-PD-1 therapy. Serum NY-ESO-1/XAGE1 Ab-positivity in HISCLTM predicted efficacy with an AUC of 0.898, resulting in a sensitivity of 86% and specificity of 93%.
Conclusions: We have developed a rapid and highly reproducible immunoassay system for detecting the serum NY-ESO-1 and XAGE1 Abs as predictive biomarkers of clinical benefits with anti-PD-1 monotherapy in NSCLC. In the future, our system would be examined in large-scale clinical trials for various other cancers.
Citation Format: Yumiko Sakai, Hirotaka Abo, Kanako Sakaeda, Yusuke Atarashi, Nobuyuki Ide, Takaaki Yamaoka, Koji Kurose, Kenta Noda, Toshiyuki Sato, Toru Oga, Mikio Oka. Development of a fully automated immunoassay system for detection of serum NY-ESO-1 and XAGE1 antibodies as biomarkers predicting the clinical efficacy of anti-PD-1 therapy [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3180.