Pembrolizumab is a humanized antibody used in cancer immunotherapy. it is an igg4 isotype antibody that blocks a protective mechanism of cancer cells, and allows the immune system to destroy those cancer cells. it targets the programmed cell death 1 (pd-1) receptor of lymphocytes.pembrolizumab is used via intravenous infusion to treat inoperable or metastatic melanoma, metastatic non-small cell lung cancer (nsclc) in certain situations, as a second-line treatment for head and neck squamous cell carcinoma (hnscc), after platinum-based chemotherapy, and for the treatment of adult and pediatric patients with refractory classic hodgkin s lymphoma (chl).