CHEMBL5733202

Homogenous Time-Resolved Fluorescence (HTRF) Binding Assay: All binding studies were performed in an HTRF assay buffer consisting of dPBS supplemented with 0.1% (withv) bovine serum albumin and 0.05% (v/v) Tween-20. For the PD-1-Ig/PD-L1-His binding assay, inhibitors were pre-incubated with PD-L1-His (10 nM final) for 15 m in 4 μl of assay buffer, followed by addition of PD-1-Ig (20 nM final) in 1 μl of assay buffer and further incubation for 15 m. PD-L1 from either human, cyno, or mouse were used. HTRF detection was achieved using europium crypate-labeled anti-Ig (1 nM final) and allophycocyanin (APC) labeled anti-His (20 nM final). Antibodies were diluted in HTRF detection buffer and 5 μl was dispensed on top of binding reaction. The reaction mixture was allowed to equilibrate for 30 minutes and signal (665 nm/620 nm ratio) was obtained using an EnVision fluorometer. Additional binding assays were established between PD-1-Ig/PD-L2-His (20 & 5 nM, respectively), CD80-His/PD-L1-Ig (100 & 10 nM, respectively) and CD80-His/CTLA4-Ig (10 & 5 nM, respectively). Competition studies between biotinylated SEQ ID NO:71 and human PD-L1-His were performed as follows. Inhibitors were pre-incubated with PD-L1-His (10 nM final) for 60 m in 4 μl of assay buffer followed by addition of biotinylated SEQ ID NO:71 (0.5 nM final) in 1 μl of assay buffer. Binding was allowed to equilibrate for 30 m followed by addition of europium crypated labeled Strepatavidin (2.5 pM final) and APC-labeled anti-His (20 nM final) in 5 μl of HTRF buffer. The reaction was allowed to equilibrate for 30 m and signal (665 nm/620 nm ratio) was obtained using an EnVision fluorometer.