LAG-3-IN-1 (Compound 11) is an inhibitor of LAG-3 with a dissociation constant (KD) of 0.41 μM. It disrupts the interaction between LAG-3 and MHCII, enhances IFN-γ secretion, and promotes tumor cell killing in co-cultures of PBMCs and cancer cells. LAG-3-IN-1 is applicable in research on cancers such as ovarian cancer, colon adenocarcinoma, and melanoma.