Real-world analysis of 2IR immune response score in histologic subtype urothelial carcinoma (hsUC).

4568 Background: The 2IR immune response score was initially developed using bulk RNA sequencing of pre-treatment tissue from ImVigor 210 and CheckMate 275 trials, however these trials enrolled patients (pts) with pure urothelial carcinoma (pUC) histology. Patients with hsUC often exhibit worse response to immune checkpoint inibitors (ICI) than patients with pUC. Here, we evaluated the 2IR score as a prognostic or predictive biomarker in real-world pts with hsUC. Methods: Specimens from pts with pUC (n = 1677) and hsUC (n = 417) were profiled at Caris Life Sciences (Phoenix, AZ) using next generation sequencing (NGS) of DNA and RNA. HsUC histologies included majority ( > 50%) squamous (n = 340), sarcomatoid (n = 51), neuroendocrine (n = 20), and micropapillary (n = 6) component. 2IR was calculated by comparative RNA expression of 10 adaptive immune genes and 39 pro-tumorigenic genes. Tumors were classified as 2IR-Low (2IR ≤ -0.5), -Mid (-0.5 < 2IR < 0), and -High (2IR ≥ 0), as previously described (Wang et al., 2022). Spearman correlation analysis was utilized to compare 2IR with tumor mutation burden (TMB), interferon score (IFN) and the tumor microenvironment (TME) cell fractions estimated using quanTIseq. Clinical outcomes included real-world overall survival (rwOS) from ICI start to last contact and time on treatment (ToT) with pembrolizumab, obtained via matched insurance claims data and calculated using Kaplan-Meier methods, while Hazard ratio (HR) was calculated by Cox proportional model. Results: For patients with hsUC, distribution of 2IR score was High 5.76%, Mid 33.3%, and Low 60.9%. Median 2IR score was significantly lower in squamous (-0.60, p < 0.0001) and sarcomatoid UC (-0.82, p < 0.0001) compared to pUC (-0.41) and significantly higher in neuroendocrine UC (-0.15, p = 0.003). Among patients with hsUC, median rwOS was significantly longer for patients with high/mid 2IR score compared to low 2IR score (25.3 [10.9-39.3] months vs. 8.7 [6.2-11.3] months; HR 0.52, 95% CI 0.34 – 0.78, p = 0.0017). ToT with pembrolizumab was also significantly longer for high/mid 2IR score compared to low 2IR score (3.0 [1.4-5.5] months vs. 2.1 [1.4-3.3] months; HR 0.68, 95% CI 0.46-1.00, p = 0.0471). Similar to pUC, 2IR score in patients with squamous UC was positively associated with CD8 T cell infiltration (r = 0.39; p < 0.0001), IFN score (r = 0.41, p < 0.0001), and TMB (r = 0.20, p < 0.001) and negatively associated with M1 macrophage infiltration (r = -0.25, p < 0.0001). 2IR scores in hsUC correlated positively but not significantly with mutations in TP53 (Median: -0.59 vs -0.62, p = 0.067) and PIK3CA (Median: -0.56 vs -0.61, p = 0.172) and negatively with mutations in CDKN2A (Median: -0.67 vs -0.59, p = 0.052). Conclusions: In a real-world cohort of patients with hsUC, we show the 2IR score may be prognostic for rwOS and predictive for pembrolizumab ToT. Prospective studies are needed to further validate this biomarker for use in this population.