Question: What are PD-1 inhibitors?

Context:
 The programmed death-1 (PD-1) pathway negatively regulates T-cell activation and has an important role in regulating antitumor host immunity. Monoclonal antibodies directed against PD-1 or the PD-1 ligand (PD-L1) have shown activity in several tumor types with preliminary data suggesting a relationship between PD-L1 expression and response.
Pembrolizumab is a selective humanized IgG4 kappa monoclonal antibody that inhibits the programmed death-1 (PD-1) receptor, an integral component of immune checkpoint regulation in the tumor microenvironment.
Checkpoint inhibitors with monoclonal antibodies targeting the CTLA-4 or PD-1 axis have revolutionized treatment in some solid tumors, especially melanoma and lung
In recent years, the introduction and Federal Drug Administration approval of immune checkpoint inhibitor antibodies has dramatically improved the clinical outcomes for patients with advanced melanoma.
Nivolumab and pembrolizumab target programmed cell death protein 1 (PD-1) receptors and have proven to be superior to ipilimumab alone. T
The Next Immune-Checkpoint Inhibitors: PD-1/PD-L1 Blockade in Melanoma
PD-1 inhibitors are also poised to become standard of care treatment for other cancers, including non-small cell lung cancer, renal cell carcinoma and Hodgkins lymphoma
PD-1 inhibitors raise survival in NSCLC
PD-1 inhibitors raise survival in NSCLC.
PD-1-PD-1 ligand interaction contributes to immunosuppressive microenvironment of Hodgkin lymphoma.
The development of programmed cell death 1 (PD-1)/PD-1 ligand 1 (PD-L1) checkpoint inhibitors has changed the landscape of non-small-cell lung cancer (NSCLC) therapy, with 2 approvals from the US Food and Drug Administration of PD-1 inhibitors for second-line therapy.
In this article, we will review the unique biologic features that predispose cHL to PD-1 inhibition, current data regarding the safety and efficacy of PD-1 inhibitors in the treatment of cHL, biomarkers of immune response, ongoing clinical trials with PD-1 inhibitors, as well as areas of uncertainty.
To determine how PD-1 signaling inhibits T cell proliferation, we used human CD4(+) T cells to examine the effects of PD-1 signaling on the molecular control of the cell cycle.
PD-1 inhibits T cell proliferation by upregulating p27 and p15 and suppressing Cdc25A.
The field of immuno-oncology has witnessed unprecedented success in recent years, with several programmed cell death 1 and PD-L1 inhibitors obtaining US FDA registration and breakthrough drug therapy designation in multiple tumor types.
The use of antibodies against programmed cell death 1 (PD-1), such as nivolumab and pembrolizumab, has dramatically improved the prognosis of patients with advanced melanoma.
 Since 2010, treatment options for metastatic melanoma have been developed including chemotherapies, checkpoint inhibition immunotherapies, e.g., anti‑cytotoxic T‑lymphocyte antigen‑4 (CTLA‑4) and anti‑programmed death‑1 (PD‑1), and molecular-targeted therapies, e.g., BRAF and MEK inhibitors. 
his strategy may be particularly advantageous for vaccines targeting prostate cancer, a disease for which antitumor vaccines have demonstrated clinical benefit and yet PD-1 pathway inhibitors alone have shown little efficacy to dat
Manipulation of co-stimulatory or co-inhibitory checkpoint proteins allows for the reversal of tumor-induced T-cell anergy observed in cancer
Colorectal cancers (CRCs) have been identified as potential targets for immunotherapy with programmed cell death (PD)-1 inhibitors
Blockading the interaction of programmed death-1 (PD-1) protein with its ligands (PD-Ls, such as PD-L1) was proved to be a pathway for suppressing the development of tumors and other degradations of biological species. Thus, finding PD-1 inhibitors situated at the convergence point of drug discovery
Anti-programmed cell death receptor-1 (PD-1) antibodies have demonstrated antitumor activity in many cancer entitie
 Emerging agents blocking the programmed cell death 1 (PD-1) pathway show activity in metastatic clear cell renal cell carci
The effectiveness of a CTLA-targeted antibody in treating melanoma was an impetus for the use of programmed cell death-1 (PD-1) inhibitors in cancer treatmen
 Monoclonal antibodies that target the programmed death-1 (PD-1)/programmed death-ligand 1(PD-L1) pathway have shown antitumour activity in metastatic renal cell carcinoma (mRCC)

Answer: The programmed death-1 (PD-1) pathway negatively regulates T-cell activation and has an important role in regulating antitumor host immunity. Monoclonal antibodies directed against PD-1 or the PD-1 ligand (PD-L1) are used to treat cancer.