The HTRF assay confirmed that compound 4b has an IC50 of 339.9 nM (see Experimental Section for details) to inhibit PD-1/PD-L1 interaction (Figure ). This is comparatively better than the IC50 of 521.5 nM for the BMS compound 4a that was synthesized and tested in our lab (BMS-1 molecule in the BMS patent WO 2015/034820 A1). It should be noted that the BMS-1 molecule was denoted with the IC50 of 6-100 nM with HTRF assay in the BMS patent . However, multiple replicates of our experiments did not result in the IC50 value less than 100 nM to inhibit PD-1/PD-L1 interaction (see Calculation of IC50 values section and Supporting File