Background: The NIVOREN GETUG-AFU 26 study reported safety and efficacy of N in mccRCC pts in a “real world setting”. A translationnal research program was launched to characterize immune cell populations in the tumor by immunohistochemistry (IHC) and correlate them with outcome on N. Methods: All pts treated with N in the GETUG AFU 26 NIVOREN trial who consented for translational program and with available archived paraffin- embedded (FFPE) tumor tissue samples were eligible. Tumor were centrally reviewed. Using IHC we quantified main immune populations (B-cells, CD8 T-cells, macrophages), and immune checkpoints receptors (TIM-3, LAG-3, PD-1) at the invasive margin (IM) and at the core of the tumor (CT). We also identified AXL and PBRM1/BAP1 expression. Results: Overall 324 pts were included. Pts had similar baseline characteristics (IMDC Good, Intermediate, Poor in 18%, 60% and 22%, respectively) and comparable outcomes than overall trial population (PFS/OS = 4.5 / 25.4 months). PD-1 (IM) expression was associated with better PFS whereas AXL expression by tumor cells (TC) was associated with worse PFS (table). LAG-3 expression tend to be associated with worse OS. PBRM-1 loss (15%) was associated with better OS and PFS and with a higher density of CD8 T-cells (p = 0.001) and CD163-macrophages (p = 0.01) (CT) and a higher expression of LAG-3 (CT) (p = 0.01) and PD-1 (CT) (p = 0.02). BAP-1 loss was not associated with PFS (p = 0.6) nor OS (p = 0.9) in this cohort. Conclusions: We report the largest translational analysis supporting that PD-1 and AXL expression are associated with PFS in pts with mccRCC receiving N. We further confirm that PBRM-1 loss is a strong prognostic factor in this setting.