Intratumoral T-cell infiltration and response to nivolumab plus ipilimumab in patients with metastatic clear cell renal cell carcinoma from the CheckMate-214 trial.

4536 Background: We have previously shown that levels of antigen-experienced but not terminally exhausted CD8 + TILs (i.e. CD8 + PD1 + TIM3 - LAG3 - TILs) are associated with improved clinical outcomes in patients (pts) with metastatic clear cell RCC (mccRCC) treated with nivolumab monotherapy within three independent clinical trials (CheckMate-010, CheckMate-025, HCRN GU16-260). Here, we aimed to evaluate the performance of this biomarker in patients with mccRCC treated with nivolumab plus ipilimumab (Nivo+Ipi) versus sunitinib (Sun) as part of the CheckMate-214 (CM-214) clinical trial. Methods: Pre-treatment, formalin fixed paraffin embedded (FFPE) tumor samples from the CM-214 clinical trial were stained with a multiplex immunofluorescence (mIF) assay and the density of CD8+PD1+TIM3-LAG3- TILs (mIF biomarker) was quantified using Halo image analysis software. The correlation between the mIF biomarker and clinical outcomes, including progression-free survival (PFS), and objective response rate (ORR), was evaluated using Cox proportional hazards and logistic regression models. The significance level was set at 5% (2-sided). Results: Following quality control, mIF data were obtained for 255 intermediate-and poor-risk patients (Nivo+Ipi= 136, Sun= 119). A comparison between patients with mIF biomarker data available and those without, showed no imbalance with regards to ORR and PFS in the Nivo+Ipi group. However, in the Sun group, pts with mIF biomarker data showed a higher ORR compared to pts without available data (33% vs 24%). In Nivo+Ipi-treated pts, the mIF biomarker measured as continuous variable showed a trend for a positive association with ORR (OR = 1.23, p = 0.1162) but no association with PFS (HR 0.97, p = 0.688). In Sun-treated pts, the mIF biomarker measured as continuous variable showed a trend for a positive association with ORR (OR = 1.32, p = 0.0726) and a significant positive association with PFS (HR= 0.78, p = 0.004. However, given that Sun-treated pts with available mIF data were enriched for responders, results obtained in the Sun group should be interpreted with caution. Conclusions: In contrast to Nivo monotherapy, pre-treatment levels of CD8+ PD1+ TIM-3-LAG-3- TILs were not associated with improved clinical outcomes to Nivo+Ipi. These results suggest that the baseline levels of intratumoral T-cell inflammation do not represent a strong determinant of response to anti-CTLA4-based therapy in mccRCC, which is consistent with the knowledge that anti-CTLA4 therapy (Ipi) can recruit new T cells into the tumor. The association between CD8+ PD1+ TIM-3-LAG-3- TILs and outcomes on sunitinib needs further investigation.