Pembrolizumab is a type of immunotherapy. It stimulates the body's immune system to fight cancercells. Pembrolizumab targets and blocks a protein called PD‐L1 on the surface of certain immune cellscalled T‐cells. Blocking the PD‐L1 protein triggers the T‐cells to find and kill cancer cells. It isadministered as a drip into a vein for 30 minutes every three weeks for up to 35 cycles.