 Checkpoint antibody inhibitors such as anti-PD1-PDL1 are a promising cancer therapeutic approach that modulate immune cell-tumor-cell interaction and yield remarkable anti-tumor responses with limited side effects. However, their efficacy is limited to specific types of cancers due to insufficient and heterogeneous expression of PD1 in the tumor microenvironment. The current landscape of the PD1-PDL1 mechanistic role in tumor immunovasion and therapeutic outcome for cancer treatment is reviewed along with progress in clinical trials, combination of drug therapy with immunotherapy, safety and future of checkpoint inhibitors for multiple types of cancer. This article was authored by Hashem O Alsab, Hashem O Alsab, some res cell, and others.