What is CAR T-cell therapy?

The immune system is made up of a variety of cells and organs, including blood cells known as T-cells.

When a foreign substance enters the body, the immune system recognises it by finding proteins called antigens on the surface of the cell. T-cells are known as immune cells, and they have their own proteins called receptors. These attach to foreign antigens and help trigger other parts of the immune system to destroy the foreign substance.

CAR T-cell therapy is a type of immunotherapy, which are therapies that strengthen the power of a patient’s immune system to recognise and attack tumours. T-cells are taken from the patient’s blood and genetically modified in the lab to allow them to bind to cancer cells to get rid of them.

At present, CAR T-cell therapy has been proven to be effective in some forms of blood cancer, such as B-cell acute lymphoblastic leukaemia, non-Hodgkins lymphoma and myeloma.

How is CAR T-cell therapy different from existing cancer treatments?

Immunotherapy is a treatment that uses a patient’s own immune system to fight cancer, compared to chemotherapy which uses drugs to kill the cancer cells directly. Chemotherapy destroys all cells, not just cancerous cells, which can result in side effects such as hair loss and nausea.

CAR T-cell treatment is associated with specific side effects which happens when the modified T-cells come into contact with cancer cells. Patients can develop fever, breathlessness and even confusion and more severe neurological complications.

Chemotherapy treatment effects only last for as long as the drugs remain in the body. CAR T-cell therapy has been shown to potentially provide long-term protection against cancer due to the T-cell’s ability to remember and recognise what cancer cells look like. That is why some call CAR T-cell therapy a living drug therapy.

Who can receive CAR T-cell therapy in Singapore?

In Singapore, Tisagenlecleucel (Kymriah), an anti- CD19 CAR T-cell therapy, is currently approved and available for:

1) young adults (under 25) with relapsed/ refractory acute B-cell lymphoblastic leukaemia;

2) adults with diffuse large B-cell lymphoma (DLBCL) that has failed to respond to 2 lines of therapy.

Large B-cell lymphoma (DLBCL) is the most common form of aggressive lymphoma in Singapore. DLBCL accounts for 30-40% of recent diagnosed cases of non-Hodgkin lymphoma globally. Patients with relapsed or refractory DLBCL have a very poor outcome. However, use of CAR T-cell therapy in these patients has demonstrated high rates of disease clearance with 40-50% of patients benefiting from a prolonged remission and overall survival.

There are presently 6 CAR T-cell therapies approved in the US, and it is expected that more therapies will be available in the next future.

CAR T-cell therapies represent a new and exciting breakthrough in the treatment for cancer patients, and in future the therapies may be directed against both blood cancers as well as solid tumour cancers.

Together with the traditional pillars of cancer therapy, CAR T-cell therapy offers another option for patients in the fight against cancer.

This article is contributed by Dr Lim Zi Yi, Medical Director and Senior Consultant Haematologist at Centre for Clinical Haematology & Visiting Consulting Haematologist at Icon Cancer Centre.

References

Cancer Fax. (2020) CAR T-Cell therapy in Singapore. Retrieved on 5 September 2022 from https://cancerfax.com/car-t-cell-therapy-in-singapore/

Sing Health. (2021). CAR T-cell Therapy. Retrieved on 5 September 2022 from https://www.singhealth.com.sg/patient-care/conditions-treatments/car-t-cell-therapy

National Cancer Institute. (2021). CAR T Cells: Engineering Patients’ Immune Cells to Treat Their Cancers. Retrieved on 5 September 2022 from https://www.cancer.gov/about-cancer/treatment/research/car-t-cells

National Cancer Institute. (2021). CAR T-cell therapy. Retrieved 5 September 2022 from https://www.cancer.gov/publications/dictionaries/cancer-terms/def/car-t-cell-therapy

American Cancer Society. (2022). CAR T-cell Therapy and Its Side Effects. Retrieved on 6 September 2022 from https://www.cancer.org/treatment/treatments-and-side-effects/treatment-types/immunotherapy/car-t-cell1.html#:~:text=In%20CAR%20T%2Dcell%20therapies,given%20back%20to%20the%20patient.

Cancer research institute. (2016) Immunotherapy vs. Chemotherapy: What’s the Difference? Retrieved on 6 September 2022 from https://www.cancerresearch.org/en-us/blog/june-2016/difference-cancer-immunotherapy-and-chemotherapy#:~:text=So%20what’s%20the%20difference%3F,identify%20and%20destroy%20cancer%20cells

Peter Mac. (2021). CAR T-CELL THERAPY. Retrieved on 7 September 2022 from https://www.petermac.org/car-t

Sing Health. (2021). A New Approach to Treating Cancer – Chimeric Antigen Receptor (CAR) T-Cell Immunotherapy. Retrieved on 7 September 2022 from https://www.singhealth.com.sg/news/defining-med/car-t-cell-immunotherapy#:~:text=In%20Singapore%2C%20tisagenlecleucel%20(Kymriah),ALL)%20and%20adults%20with%20DLBCL