How CAR T-Cell Therapy Works—Cancer's Living Drug
CAR T-cell therapy reprograms a patient's own immune cells to hunt and destroy cancer. Here's how the process works, what it costs, and why scientists are now using it against autoimmune diseases.
Turning Immune Cells Into Cancer Killers
Every human body comes equipped with T cells—white blood cells that patrol the bloodstream and destroy infected or abnormal cells. But cancer often evades them. Tumour cells can disguise themselves, suppress immune signals, or simply multiply faster than T cells can respond.
Chimeric antigen receptor T-cell therapy, known as CAR T-cell therapy, changes the equation. It takes a patient's own T cells, genetically engineers them in a laboratory to recognise a specific protein on cancer cells, and infuses them back into the body as a precision-guided weapon. Oncologists call it a "living drug" because, unlike a pill or infusion that degrades over time, CAR T cells can multiply inside the body and keep fighting for months or even years.
The Five-Step Process
The therapy follows a carefully choreographed sequence:
- Collection (leukapheresis): Doctors draw blood and separate out the patient's T cells using a specialised machine.
- Engineering: In a lab, scientists use a disabled virus to insert a new gene into the T cells. This gene codes for a chimeric antigen receptor—a synthetic protein that sits on the cell surface and locks onto a target molecule found on cancer cells, most commonly CD19, a protein on the surface of B cells.
- Expansion: The modified cells are grown in bioreactors until they number in the hundreds of millions.
- Conditioning: The patient receives a short course of chemotherapy to deplete existing immune cells and make room for the engineered ones.
- Infusion: The CAR T cells are dripped into the bloodstream, where they begin seeking out and destroying target cells.
The entire manufacturing process typically takes three to four weeks—a delay that can be critical for patients with aggressive cancers.
What It Treats—and What It Costs
The U.S. Food and Drug Administration has approved six CAR T-cell products since 2017, when tisagenlecleucel (Kymriah) became the first to reach the market for paediatric acute lymphoblastic leukaemia. All currently approved therapies target blood cancers—leukaemias, lymphomas, and multiple myeloma. Solid tumours remain a major frontier, as they create hostile microenvironments that suppress engineered T cells.
The price tag is steep. The drug alone costs between $373,000 and $475,000 per infusion, according to a 2022 analysis in the British Journal of Cancer. When hospitalisation, monitoring, and management of side effects are included, total costs can exceed $600,000, with some cases surpassing $1 million.
The Risks: Cytokine Storms and Beyond
CAR T-cell therapy can trigger severe side effects. The most common is cytokine release syndrome (CRS), in which the newly activated T cells flood the bloodstream with inflammatory signalling molecules called cytokines. Symptoms range from high fevers and low blood pressure to, in rare cases, organ failure. Doctors now manage CRS with drugs like tocilizumab, an anti-inflammatory that blocks a key cytokine receptor.
A second concern is immune effector cell–associated neurotoxicity syndrome (ICANS), which can cause confusion, seizures, and difficulty speaking. Both CRS and ICANS are usually reversible, but require close monitoring in specialised medical centres.
Beyond Cancer: Autoimmune Breakthroughs
Perhaps the most exciting recent development is the use of CAR T cells against autoimmune diseases. In autoimmune conditions like lupus, rogue B cells produce antibodies that attack the patient's own tissues. Because CAR T cells targeting CD19 destroy B cells, researchers hypothesised they could reset a malfunctioning immune system.
The results have been striking. A STAT News report from April 2026 noted that five years after the first lupus patients received CAR T cells at Germany's University of Erlangen, researchers continue to see durable remissions. As of mid-2025, over 160 clinical trials were testing CAR T cells in autoimmune diseases including lupus, inflammatory myositis, and systemic sclerosis.
What Comes Next
Two innovations aim to solve the therapy's biggest limitations—manufacturing time and cost. Off-the-shelf CAR T cells, made in advance from healthy donor cells, could eliminate the weeks-long wait. Meanwhile, researchers at Duke University and others are developing in vivo approaches that use lipid nanoparticles to reprogram T cells directly inside the patient's body, skipping the laboratory entirely.
If these next-generation methods succeed, CAR T-cell therapy could shift from a last-resort treatment costing half a million dollars to a widely accessible medicine—one that harnesses the body's own defences against diseases it was never designed to fight alone.
