Urinary RNA as response predictor for patients with metastatic urothelial carcinoma treated with pembrolizumab.

Abstract

e16591 Background: Limited biomarkers are available to predict response and outcome in metastatic urothelial carcinoma (mUC) patients treated with pembrolizumab. The Belgian multicenter CORPORA study evaluates the use of tissue, plasma and urine RNA as companion diagnostic in this setting. Results for plasma and urine will be presented. Methods: Baseline plasma (n = 41) and urine (n = 27) were prospectively collected in mUC patients receiving pembrolizumab (200 mg Q3W). Cell-free RNA (cfRNA) isolation and library prep, using Illumina RNA prep with enrichment, was followed by short read RNA sequencing (15M reads/sample). Data analysis included principal component analysis (PCA), differential gene expression (DGE), and gene set enrichment analysis (GSEA). Association to response (RECIST 1.1), survival, and occurrence of immune-related adverse events (irAEs) was determined. Results: PCA of plasma and urine did not reveal any sample clustering. Further downstream DGE indicated no significant difference in plasma cfRNA single gene abundance for response, outcome, or irAEs. In contrast, DGE in urine identified four significantly downregulated genes ( C12orf75 , RPS28P7 , ENSG00000267469 , RPL36AP37 ) and one significantly upregulated gene ( CIDEC ) that differentiate responders from non-responders. Regarding outcome, 5 genes ( ALKBH8 , FSIP1 , GDE1 , HMGB3 , and RHOU ) were identified as candidates for progression-free survival (PFS) and overall survival (OS, Table). A total of 271 genes, including the five genes identified for outcome, were significantly differentially abundant between patients who developed grade 3+ irAEs compared to those with milder grade 1-2 toxicity. GSEA indicated responders to exhibit cellular reprogramming toward enhanced metabolic fitness and tissue remodeling, whereas non-responders show a more stress-associated transcriptional state with altered immune, cell death, and mitochondrial respiration programs. Development of irAEs on the other hand was associated with broad immune hyperactivation and tissue remodeling programs, accompanied by suppression of mitochondrial oxidative metabolism. Conclusions: Urinary cfRNA contains candidate biomarkers for pembrolizumab response prediction, prolonged survival, and the occurrence of more severe irAEs. Further research is ongoing, including comparison to tissue RNA, and study of circular RNA, fusion genes, and immune cell enumeration via deconvolution. Cox regression univariate analysis for urine mRNA and survival. PFS OS Gene HR (95% CI)* P HR (95% CI)* P ALKBH8 0.46 (0.27-0.78) 0.004 0.58 (0.35-0.95) 0.030 FSIP1 0.55 (0.31-0.96) 0.036 0.37 (0.19-0.71) 0.003 GDE1 0.49 (0.25-0.94) 0.032 0.53 (0.29-0.96) 0.037 HMGB3 0.51 (0.31-0.84) 0.009 0.36 (0.17-0.73) 0.005 RHOU 0.57 (0.34-0.94) 0.028 0.38 (0.19-0.79) 0.009 *HRs representing change in risk per one standard deviation increase in gene expression.