Systematic analysis the genomic and microenvironment characteristics with the status of human leukocyte antigen (HLA) and the integration of HLA LOH, TMB and PD-L1 could further distinguish the responders to immunotherapy.

e20529 Background: Although studies have shown that loss of heterozygosity (LOH) at the human leukocyte antigen (HLA) locus is one of the mechanisms of immune escape, the effect of HLA LOH on the immune checkpoint inhibitors (ICIs) treatment is still need to be further investigated, especially for the patients with positive programmed cell death-Ligand 1 (PD-L1) expression and high tumor mutation burden (TMB). Methods: 425 sample of Chinese lung cancer patients who received PD-L1 immunotherapy were performed with targeted panel sequencing to analyzed the genomic characteristics with HLA status. 994 non-small cell lung cancer (NSCLC) sample from The Cancer Genome Atlas (TCGA) were used to analyze the impact of HLA LOH on the tumor microenvironment. In addition, 89 samples from previous study were used to analyze the association of HLA status with the ICIs treatment in NSCLC. Results: The genomic characteristics from 425 sample of Chinese lung cancer patients who received PD-L1 immunotherapy were analyzed. We found that mutation frequency of driver genes and TMB in the HLA LOH high group were significantly increased. Transcriptome analysis revealed HLA LOH played a critical role in the tumor immune microenvironment in PD-L1 + /TMB-H population and the impact on lung adenocarcinoma was greater than that on lung squamous cell carcinoma. Progression-free survival of PD-L1 + /TMB-H population was significantly decreased in HLA LOH group which suggest that comprehensive considering HLA LOH as a biomarker may improve clinical response to immunotherapy. Conclusions: This work showed the genomic and immune microenvironment characteristics of HLA LOH and demonstrated HLA LOH as a significant negative predictor of outcomes after ICIs treatment, especially in PD-L1 + /TMB-H population. These data suggested that comprehensive considering HLA LOH as a biomarker may improve clinical response to immunotherapy.