Disclosed herein are compositions including a compound of formula (I) for treating cancer. Some embodiments relate to methods of treating cancer by co-administering a compound of formula (I) and one or more immune checkpoint inhibitor to a subject in need thereof, in particular, combinations of tucaresol and immune checkpoint inhibitors of PD-L1, PD-L2, or CTLA-4. Some embodiments relate to methods of treating cancer by co-administering a compound of formula (I) and plinabulin to a subject in need thereof. Some embodiments relate to methods of providing co-stimulation of T-cell activation against cancer by co-administering a compound of formula (I), one or more immune checkpoint inhibitor.
