Abstract 2278: Dissecting immuno-genomic pathways of response and resistance to immunotherapy in metastatic urothelial carcinoma in a real-world cohort

Abstract Background: While Immune Checkpoint Inhibitors (ICI) are widely used for the treatment (tx) of patients (pts) with metastatic urothelial carcinoma (mUC), response rates are only around 20%. There is an unmet need to develop biomarkers of response and resistance to avoid unnecessary treatment in the majority of pts who will not respond to ICI, to spare toxicity from ICI as well as mitigate the financial burden. Here we report tumor immune-genomic characteristics associated with response and resistance to ICI in a real-world cohort of mUC pts at the Cleveland Clinic. Methods: We selected 61 mUC pts who received at least 2 cycles of ICI (atezolizumab or pembrolizumab) between 2015-2020 and had pre-tx archival fresh frozen paraffin-embedded (FFPE) tissues available. Pts were categorized by their response to ICI as complete responders (CR; N=8), partial responders (PR; N=14), stable disease (SD; N=9), and progressive disease (PD; N=30). Tumor was macrodissected from 2-5 FFPE slides guided by an H&E stained section of tumor. RNA extraction was done using Qiagen Rneasy FFPE kit. 100ng of RNA was used for transcriptomic analysis using the 770-gene Nanostring PanCancer IO 360 panel. Data normalization and analysis was carried out using nSolver 4.0. Results: Using unsupervised hierarchical clustering, when comparing molecular signatures of pts with CR vs PD respectively, we saw upregulation of exhausted CD8 (log fold change (FC) = 0.7287, p= 0.03289) and IFN downstream (logFC = 0.5929, p = 0.04986). Notably, the molecular signatures upregulated between SD vs PD respectively were IFN Gamma (logFC = 1.503, p = 0.0044), PD-L1 (logFC = 1.136, p = 0.0123), Antigen-presenting machinery (APM) (logFC = 1.103, p = 0.0006), Immunoproteasome (logFC = 0.984, p = 0.00096) and Tumor inflammatory score (logFC = 0.947, p = 0.032). Furthermore, molecular signatures were not differently upregulated between pts with PR vs PD. In our cohort, the proportion of pts who were alive at 35.9 months (median follow-up) was 62.5% for CR (5 of 8), 28.5% for PR (4 of 14), 22.2% for SD (2 of 9) and 6.2% for PD (2 of 30) even though the median overall survival was not significantly different between the groups. Conclusion: In our cohort of ICI-treated mUC pts, we found an association between existing T-cell effector function, particularly IFN-gamma responses, and response to ICI. Signatures associated with T cell exhaustion were also upregulated among pts with CR indicating ongoing anti-tumor activity. These findings need to be further validated in prospective trials. Ongoing genomic and immunologic correlative studies in our cohort will further help understand comprehensive biomarkers of response and resistance to ICI in pts with mUC are currently underway. Citation Format: Nikhil Pramod, Paul Pavicic, Scott Dawsey, Alan Shen, Roshan Lodha, Moshe Ornstein, Omar Mian, Timothy Gilligan, Christopher Wee, Amanda Nizam, Jane Nguyen, C. Marcela Diaz-Montero, Shilpa Gupta. Dissecting immuno-genomic pathways of response and resistance to immunotherapy in metastatic urothelial carcinoma in a real-world cohort [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2278.