Abstract 7611: Circulating blood RNAseq detects activation of immune system and predicts response to immunotherapy in bladder cancer

Abstract Background: Anti-PD (L) 1 immunotherapies have revolutionized oncology by getting durable tumor responses in advanced cancers. Nevertheless, currently approved biomarkers (PD-L1, MSI, TMB) have suboptimal positive/negative predictive values for tumor responses and survival. Aims 3 months showed an overexpression of 25 genes associated with immune cells activation such as CD8A, CXCL8, EOMES, FASLG, GZM genes, whereas patients with a shorter PFS highly expressed genes of immune cell inhibition: CD177, CD300LG, CD99, and CST7. Finally, patients with an OS 7 months had also a higher expression of the same previous genes completed with 6 other genes, still indicators of immunity activation (CD3D, CD3E, CD3G, GZMM, IL2RB, and PTGDS). Conclusion: Total RNAseq from RNA directly extracted from whole blood can detect baseline activation of T-cells in patients who will subsequently benefit from anti-PD-L1 immunotherapy. This work shows that RNAseq can detect an immune activation state in circulating blood without specific cell selection. This technique could be used in clinical trials to select for patients prone to benefit from cancer immunotherapies. Citation Format: Corentin Richard, Sandy Chevrier, Aurélien Marabelle, Romain Boidot. Circulating blood RNAseq detects activation of immune system and predicts response to immunotherapy in bladder cancer abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 7611.