IMMUNOTHERAPY: PROMISING NEW CANCER THERAPY
The immune system is a host defense system that protects against illness and infections. Cancer cells thrive because they are able to hide from the immune system.
Immunotherapy is a treatment that helps the immune system or uses certain parts of a person’s immune system to fight diseases, and it has become a promising alternative therapeutic approach for cancer patients. Certain immunotherapies can mark cancer cells so it is easier for the immune system to find and destroy them (monoclonal antibodies). Other types of immunotherapies boost your immune system to work better against cancer (immune checkpoint inhibitors, adoptive cell transfer, cytokines, treatment vaccines or Oncolytic virus therapy).
The immune system leaves the normal cells alone, while attacking the foreign or abnormal cells that are potentially dangerous to our body. To do this, the immune systems uses “checkpoints”, which are molecules presented on certain immune cells that need to be activated in order to initiate an immune response. The “immune checkpoints” are regulators of the immune system and prevent the immune system from attacking cells. The inhibitory checkpoint molecules, as CTLA-4 and PD-1, act as “off” switches when bound to their ligands.
Immune checkpoints inhibitors work by releasing the brakes on the immune system so it can destroy cancer cells. Once the immune checkpoints are inhibited, the immune system can detect and attack cancer cells more efficiently, therefore stopping or slowing cancer growth. Several immune checkpoint inhibitors are already approved by the Food and Drug Administration (FDA) and European Medicines Agency (EMA). The first such drug to receive approval was ipilimumab (Yervoy) to treat advanced melanoma.
CTLA-4 Inhibitors target CTLA-4 (Cytotoxic T-Lymphocyte-Associated protein 4) which is a protein receptor on some T cells that downregulates immune responses, acting as an“off switch” that prevents T cell proliferation. Ipilimumab is a monoclonal antibody that blocks the activity of CTLA-4, which can boost the body’s immune response against cancer cells.
PD-1 / PD-L1 Inhibitors PD-1 (Programmed Death 1) is a receptor that plays an important role in down-regulating the immune system, promoting apoptosis (cell death) in certain T-cells. PD-1 negatively regulates the immune system when it is attached to its ligand, PD-L1. Some cancer cells have large amounts of PD-L1, which helps them evade immune attack. Drugs that target either PD-1, as pembrolizumab (Keytruda) and nivolumab (Opdivo), or PD-L1, as atezolizumab (Tecentriq), avelumab (Bavencio) and durvalumab (Imfinzi), can block this binding and boost the immune response against cancer cells. These drugs have shown a great deal of promise in treating certain cancers.
Many other immunotherapies are now being tested in clinical trials as well, both alone and in promising combinations.