What is immunotherapy?
- Immunotherapy is defined as one of the methods of treatment by inducing, enhancing, or suppressing an immune response.
- It is one of the types of biological therapy in which the substances obtained from living organisms are used to treat cancer.
- Generally, immunotherapies are classified into two groups:
- Activation immunotherapies: includes immunotherapies employed for amplifying an immune response.
- Suppression immunotherapies: includes immunotherapies that suppress or reduce an immune response.
- Mostly, immunotherapies have been found to be promising to cure varieties of cancer.
- Also, it often has fewer side effects in comparison to the existing drugs.
Relation between immunotherapy and immune system:
- Immunotherapy helps to enhance immune cells by providing with additional components.
- Immunotherapy instructs the immune system to identify and defend specific cancer cells.
- Immunotherapy helps to eradicate cancer by boosting immune cells.
Types of Immunotherapy for cancer:
There are various types of immunotherapy. They are listed as follows:
- Monoclonal antibodies and tumor-agnostic treatments, such as checkpoint inhibitors
- Oncolytic virus therapy
- CAR T-cell therapy
- Cancer vaccines
- Immune checkpoint inhibitors
1. Monoclonal antibodies (mAbs or MoAbs) and tumor-agnostic treatments:
- When a threat is sensed by the immune system, it produces antibodies.
- Antibodies are proteins that interact with antigens and initiate an immune response in the body.
- Monoclonal antibodies are defined as antibodies that are prepared in laboratory in order to boost the natural antibodies or to defend the foreign threats itself.
- Monoclonal antibodies help to fight cancer in several ways, for instance, monoclonal antibodies can be designed to fight with a specific cancer cell.
- Thus, it is also termed as targeted therapy.
- Basically, three types of mAbs are introduced, they are:
- i. Naked monoclonal antibodies:
- Most commonly used for treatment of cancer.
- They are not attached to any other substance.
- These antibodies instruct the immune system to defend cancer cells or block proteins within tumor.
- ii. Conjugated monoclonal antibodies:
- These are attached with either a radioactive particle or chemotherapy drug.
- They are capable of attaching directly to the cancer cells.
- It works by delivering the drug to the location of utmost requirement.
- There are reduced or less chance of side effects and enhances the chemotherapy as well as radiation.
- iii. Bispecific monoclonal antibodies (BsMAb):
- These are antibodies designed in order to bind with two proteins at once.
- Few can bind to both cancer cells and an immune system cell facilitating the immune response on cancer.
- i. Naked monoclonal antibodies:
2. Oncolytic virus therapy:
- In this type of treatment, viruses used are modified in the lab with a motive to infect and kill specific tumor cells.
- Procedure of Oncolytic virus therapy:
- First, the genetically modified virus is injected into the tumor.
- Then the virus reaches the cancer cells and make copy of itself.
- This leads to the disruption of cancer cells and ultimately their death.
- As soon as the cells die, it stimulates the immune system to attack any cancer cells on the body having alike proteins as that of dead cells.
- This modified oncolytic virus doesn’t affect healthy cells.
- This therapy is considered superior to all other immunotherapies as it does not depend on any specific antigen expression patterns.
- The features that makes it an ideal candidate for the treatment of diverse malignancies are as follows:
- Oncolytic viruses enhance the recruitment of tumor-infiltrating lymphocytes (TILs)
- Reprogramming of immunosuppressive tumor micro-environment (TME)
- Boosts systemic anti-tumor immunity
3. CAR T-cell therapy:
- It stands for chimeric antigen receptor T-cell therapy (CAR T-cell therapy).
- T cell, a type of leukocytes is one of the main constituents of the adaptive immune system.
- In CAR T-cell therapy, the doctor reprograms T cells after taking out T cells from blood in order to find cancer cells more easily in contrast to it, T-cell therapy instruct the T-cells to search for tiny bits of specific antigens inside the cancer cells.
- Procedure of CAR T-cell therapy:
- At first T cells are isolated from patient’s blood.
- Then, the receptors, which are specific proteins are added to it in the laboratory.
- The receptors permit the T cells to identify cancer cells.
- Then, the programmed T cells are then re-entered into the body.
- Now, these cells find and destroy cancer cells.
- Side effects such as low blood pressure, fever, confusion, and in rare cases, seizures are observed.
4. Cancer vaccines:
- These are also termed as therapeutic vaccines.
- The vaccines are employed to people already diagnosed with cancer with a motive to increase body’s natural defense in order to fight cancer.
- The vaccines may either prevent the cancer from recurrence, destroy any cancer cells remnant even after the accomplishment of other treatments or stop a tumor from spreading.
- Procedure of cancer vaccine therapy:
- As we know, when the antibodies are produced in response to the antigens, the immune system develops memory cells, which will respond to these antigens in future.
- Cancer vaccines enhance the immune system’s capacity to identify and destroy antigens.
- Certain molecules termed as cancer specific antigens are present on the surface of the cancer cells, which are lacked by healthy cells.
- These molecules act as antigens when given to a person, and trigger the immune system to identify and kill cancer cells having these molecules on the surface.
- Few cancer vaccines also consist of adjuvants that may enhance the immune response.
5. Immune-checkpoint inhibitors:
- It is the significant function of immune cells to be able to differentiate between the own normal cells and foreign cells.
- Checkpoints are thus required, in order to monitor the foreign cells.
- In general term, immune checkpoints are molecules on specific immune cells that needs to be either activated or inactivated for starting an immune response.
- Drugs targeting these checkpoints are found to be promising for cancer treatment.
- These drugs are hence termed as checkpoint inhibitors.
- Two types of checkpoint inhibitors are described on the basis of proteins they target, they are:
- i. Checkpoint inhibitors that target PD-1 or PD-L1:
- T cells are immune cells and PD-1 is a checkpoint protein on it.
- PD-1 protein prevents the T-cells from attacking other cells in the body, acting as a type of off switch.
- It occurs when it is bound to PD-L1, which is a protein on some normal and cancer cells.
- After the binding, it stops T-cells from attacking any cells favoring the cancer cells with high PD-L1 protecting it from immune attack.
- Monoclonal antibodies targeting either PD-1 cells or PD-L1 cells can prevent the binding and enhance immune response against cancer cells.
- Drugs targeting PD-1 (PD-1 inhibitors):
- Pembrolizumab (Keytruda)
- Nivolumab (Opdivo)
- Cemiplimab (Libtayo)
- Drugs targeting PD-L1 (PD-L1 inhibitors):
- Atezolizumab (Tecentriq)
- Avelumab (Bavencio)
- Durvalumab (Imfinzi)
- Drugs targeting PD-1 (PD-1 inhibitors):
- ii. Checkpoint inhibitors that target CTLA-4
- Some T cells contain CTLA-4 protein that also acts as a off switch inorder to regulate immune system.
- The CTLA-4 is inhibited by Ipilimumab (Yervoy) which is a monoclonal antibody that attaches to CTLA-4.
- The body’s immune response is hence improved.
- This drug is proved to treat melanoma of skin.
- Side effects of checkpoint inhibitors include:
- – Inflammation in the lungs
- – Rashes along with itchiness
- – Kidney infections
- – Diarrhea