What Is Immunotherapy?

More and more, cancer patients are being treated with immunotherapy. It’s an innovative treatment that uses certain components of a patient’s immune system to fight cancer. It works by stimulating a patient’s immune system to target cancer cells or by introducing human-made immune system proteins and other elements into the body.

The idea that the immune system could be harnessed to fight cancer was developed more than 30 years ago at the National Cancer Institute. Groundbreaking research led to the development of the first immunotherapy, monoclonal antibodies, in 1984. That was followed by the identification of checkpoint inhibitors in the early 2000s and eventually the creation of chimeric antigen receptor T-cell therapy (CAR T), which was approved by the Food and Drug Administration to treat blood cancers in 2017, and tumor-infiltrating lymphocyte therapy (TIL), which was FDA approved for advanced melanoma in 2024.

Several types of immunotherapy can be used to treat cancer, including:

Adoptive cell transfer — T cells, which are part of the immune system, are removed from a patient, multiplied in the lab and then reinfused into the patient. Examples include:

• CAR T-cell therapy — A patient’s T cells are genetically modified in the lab to recognize the unique proteins that are present on the surface of cancer cells and programmed to destroy cancerous cells. It is FDA approved for patients with diffuse large B cell lymphoma, mantle cell lymphoma, acute lymphoblastic leukemia, multiple myeloma, follicular lymphoma, transformed follicular lymphoma and primary mediastinal B cell lymphoma.
• TIL therapy — TILs, which are an immune cell, are harvested from cancerous tissue collected during surgery. They are grown to billions in the lab and infused back into the patient to attack cancer. It is FDA approved to treat advanced melanoma, and multiple trials are ongoing to investigate the treatment in other solid tumor cancers, such as sarcoma, lung and cervical cancer.
• T-cell receptor therapy — TCR therapy involves the modification of T cells in a lab, but this immunotherapy is unique in that it can recognize many types of cancer that have overexpression of a specific antigen within the cell. In studies, the therapy has effectively destroyed blood, lung, breast, prostate, colon, bone, skin, kidney, ovarian and cervical cancer cells while ignoring healthy cells.

Cancer vaccines — Vaccines are injected into the body to stimulate the immune system, essentially training it to destroy cancer.

Cytokines — Human-made cytokines, a group of proteins found naturally in the body, can send signals to help destroy cancer cells and enable normal cells to live longer. Other types of cytokines can be used to either prevent or manage side effects associated with chemotherapy.

Immune checkpoint inhibitors — These drugs block checkpoint proteins, effectively “releasing the brakes” on the immune system and bolstering its ability to fight cancer. Examples include:

• Ipilimumab (Yervoy) blocks the immune checkpoint protein CTLA-4 and can be used to treat several types of cancers such as melanoma, non-small cell lung cancer and kidney cancer.
• Pembrolizumab (Keytruda) and nivolumab (Opdivo) block the immune checkpoint known as PD-1 and can be used to treat several cancers: bladder, breast, kidney, head and neck, non-small lung, melanoma and Hodgkin lymphoma.
• Atezolizumab (Tecentriq), avelumab (Bavencio) and durvalumab (Imfinzi) block the immune checkpoint PD-L1. They are used to treat Merkel cell carcinoma, as well as bladder, breast and non-small cell lung cancer.

Monoclonal Antibodies — An antibody is a Y-shaped protein that binds to a foreign invader called an antigen, signaling to other immune cells they need to attack. A monoclonal antibody is a human-made version of the antibody that is produced in a laboratory and infused back into the patient.

Oncolytic Viruses — Oncolytic virus immunotherapy typically involves injecting a genetically modified virus into a tumor to kill cancer cells and trigger a response from the immune system. In 2015, the FDA approved talimogene laherparepvec, or T-VEC, a genetically modified form of the herpes simplex virus used to treat patients with metastatic melanoma that cannot be surgically removed. It is also being studied in triple-negative breast cancer and lung cancer.