Given the facts that the serum concentration reached in patients is around 6 μM (Baddeley et al, 2015) and that IC50 to effectively enhance cytotoxicity of CTL is well below micromolar, it is a tempting hypothesis that MB be a highly effective PD‐1 inhibitor in clinic for treating cancer patients either by itself or in combination with other drugs. This evidence concerns the gene PDCD1 and cancer.