Immunohistochemistry studies were performed on formalin-fixed and paraffin-embedded (FFPE) tissue sections collected by the study sponsors at the time of the trials. An in-house double IHC staining assay was developed using an extensively validated antibody against PD-L1 (405. 9A11 mouse monoclonal antibody, 1:100, 13 micrograms/ml, Dr. Freeman laboratory, Dana-Farber Cancer Institute, Boston, MA, USA and commercially available through Cell Signaling Technology (CST))(23 (link)-27 (link)) and a cocktail of antibodies recognizing immune cells consisting of anti-CD45 (1:500, D9M8I XP, rabbit monoclonal antibody, CST) with anti-CD163 (1:5000, EPR19518, rabbit monoclonal antibody, Abcam). Tumor sections were stained with Bond Rx Autostainer (Leica Biosystems, Buffalo Grove, IL) using the Bond Polymer Refine Detection Kit (DS9800; Leica Biosystems) and Bond Polymer Refine Red Detection Kit (DS9390, Leica Biosystems). Antigen retrieval was performed with Bond Epitope Retrieval Solution 2 (EDTA, pH = 9.0) for 30 minutes. All slides were counterstained with hematoxylin, dehydrated in graded ethanol and xylene, mounted, and cover slipped (Supplementary Figure 1).