PD-1/PD-L1

PD-1 (Programmed Death 1) is a protein on the surface of T cells, the immune system's main cancer-fighting cells. PD-L1 is a partner protein that some tumors display to switch those T cells off. When PD-1 and PD-L1 connect, the immune system stops attacking, which is why drugs that block this connection (checkpoint inhibitors) can wake the immune system back up against the cancer.

Origin

PD-1 was discovered in 1992 by Tasuku Honjo's lab at Kyoto University while studying programmed cell death in immune cells. PD-L1 was identified later as its binding partner. Honjo shared the 2018 Nobel Prize in Medicine with James Allison for showing that blocking these checkpoint proteins could treat cancer.

Significance in Asbestos Context

For mesothelioma patients, the PD-1/PD-L1 pathway is the basis of the immunotherapy combination nivolumab (Opdivo) plus ipilimumab (Yervoy), which the FDA approved in 2020 as first-line treatment for unresectable pleural mesothelioma. This was the first major advance in front-line mesothelioma therapy in over 15 years and is now a standard option alongside or instead of chemotherapy. Tumor tissue from your biopsy can be tested for PD-L1 expression, which helps your oncologist predict how well immunotherapy may work, though patients with low PD-L1 levels can still respond. Non-epithelioid mesothelioma (sarcomatoid and biphasic subtypes) tends to respond especially well to this combination compared with chemotherapy.

Example Sentence

After her pleural mesothelioma was diagnosed as the sarcomatoid subtype, her oncologist recommended a PD-1/PD-L1 checkpoint inhibitor combination rather than traditional chemotherapy.

Related Terms

Immunotherapy, Checkpoint Inhibitor, Nivolumab, Ipilimumab, Mesothelioma, Tumor Microenvironment

Notes

• Ask your oncologist whether your tumor has been tested for PD-L1 expression and what your score (TPS or CPS) was. Request this be added to your pathology report.
• Ask specifically about the nivolumab + ipilimumab regimen (CheckMate 743 trial) if you have pleural mesothelioma, especially if your subtype is sarcomatoid or biphasic.
• Watch for and immediately report immune-related side effects: persistent diarrhea, new rash, shortness of breath, unusual fatigue, or thyroid symptoms. These can become serious if not treated early with steroids.
• Keep copies of your pathology report, PD-L1 testing results, and all immunotherapy infusion records; these document your treatment course and costs for any legal claim.
• Ask whether you qualify for clinical trials combining checkpoint inhibitors with chemotherapy, radiation, or newer agents, as this is an active area of mesothelioma research.