Question: What is targeted by monoclonal antibody Pembrolizumab?

Context:
gents currently in active clinical development for lung cancer include ipilimumab, which modulates the cytotoxic T-lymphocyte-associated antigen 4 pathway, and multiple agents targeting the programmed death protein 1 (PD-1) pathway, both anti-PD-1 compounds (nivolumab, pembrolizumab [MK-3475]) and those that target programmed death ligand 1 (PD-L1), a key ligand for PD-1 (BMS-936559, MPDL3280A). 
Ipilimumab (CTLA-4) and pembrolizumab (PD-1) are approved by the US Food and Drug Administration for the treatment of advanced melanoma, and additional regulatory approvals are expected across the oncologic spectrum for a variety of other agents that target these pathways.
Pembrolizumab inhibits the programmed cell death 1 (PD-1) immune checkpoint and has antitumor activity in patients with advanced melanoma.
CONCLUSIONS: The anti-PD-1 antibody pembrolizumab prolonged progression-free survival and overall survival and had less high-grade toxicity than did ipilimumab in patients with advanced melanoma. 
METHODS: We conducted a phase 2 study to evaluate the clinical activity of pembrolizumab, an anti-programmed death 1 immune checkpoint inhibitor, in 41 patients with progressive metastatic carcinoma with or without mismatch-repair deficiency.
CONCLUSIONS: This study showed that mismatch-repair status predicted clinical benefit of immune checkpoint blockade with pembrolizumab. 
The anti programmed cell death-1 (PD-1) antibodies pembrolizumab and nivolumab have been recently licensed by the Food and Drug Administration for the treatment of advanced melanoma. 
We describe for the first time the case of an adult patient who developed autoimmune diabetes likely as a consequence of PD-1 inhibition with pembrolizumab. 
Ipilimumab, an anti-cytotoxic T-lymphocyte antigen 4 antibody and pembrolizumab, a monoclonal antibody targeting programmed death 1 receptor may be a feasible treatment option in patients with metastatic mucosal melanoma
Pembrolizumab, a humanized highly selective IgG4 anti-PD-1 monoclonal antibody, was recently approved for the treatment of advanced melanoma based on promising early-phase clinical data
Anti-programmed-death-receptor-1 treatment with pembrolizumab in ipilimumab-refractory advanced melanoma: a randomised dose-comparison cohort of a phase 1 trial.
Efficacy was similar in the two pembrolizumab groups. Rates of treatment-related adverse events of grade 3 to 5 severity were lower in the pembrolizumab groups (13.3% and 10.1%) than in the ipilimumab group (19.9%).CONCLUSIONS: The anti-PD-1 antibody pembrolizumab prolonged progression-free survival and overall survival and had less high-grade toxicity than did ipilimumab in patients with advanced melanoma. 
BACKGROUND: The anti-programmed-death-receptor-1 (PD-1) antibody pembrolizumab has shown potent antitumour activity at different doses and schedules in patients with melanoma. We compared the efficacy and safety of pembrolizumab at doses of 2 mg/kg and 10 mg/kg every 3 weeks in patients with ipilimumab-refractory advanced melanoma.METHODS: In an open-label, international, multicentre expansion cohort of a phase 1 trial, patients (aged ?18 years) with advanced melanoma whose disease had progressed after at least two ipilimumab doses were randomly assigned with a computer-generated allocation schedule (1:1 final ratio) to intravenous pembrolizumab at 2 mg/kg every 3 weeks or 10 mg/kg every 3 weeks until disease progression, intolerable toxicity, or consent withdrawal. 
Vemurafenib and dabrafenib are targeted agents for patients with BRAF mutation-positive melanoma. Ipilimumab, an anti-cytotoxic T-lymphocyte antigen 4 antibody and pembrolizumab, a monoclonal antibody targeting programmed death 1 receptor may be a feasible treatment option in patients with metastatic mucosal melanoma.
Pembrolizumab, a humanized highly selective IgG4 anti-PD-1 monoclonal antibody, was recently approved for the treatment of advanced melanoma based on promising early-phase clinical data. Encouraging results have also been seen in other malignancies, and PD-1-targeted therapies are likely to markedly change the treatment landscape.

Answer: Pembrolizumab inhibits the programmed cell death 1 (PD-1) immune checkpoint and has antitumor activity in patients with advanced melanoma. Pembrolizumab is approved by the US Food and Drug Administration for the treatment of advanced melanoma, and additional regulatory approvals are expected across the oncologic spectrum for a variety of other agents that target these pathways.
Exact answer: programmed cell death 1