Cell therapy is a broad category of medical treatment in which living human cells are used to repair, replace, or reprogram damaged tissue or a malfunctioning immune system. Some forms have been around for decades (bone marrow transplants are a type of cell therapy), while others, like genetically engineered immune cells that hunt cancer, were first approved only in 2017. The FDA now lists 49 approved cellular and gene therapy products, treating conditions from blood cancers and sickle cell disease to Type 1 diabetes and severe burns.
How Cell Therapy Works
All cell therapies share a basic premise: introduce living cells into the body to do something the body can no longer do on its own. Beyond that, the specific mechanisms vary widely. Some therapies directly replace missing or damaged cells. Transplanted insulin-producing cells for diabetes, for instance, take over a job the patient’s own pancreas has lost the ability to perform. Other therapies work by modulating the immune system, either calming an overactive response (as in autoimmune diseases) or supercharging immune cells to attack cancer.
A third mechanism involves what scientists call paracrine signaling. Rather than doing the repair work themselves, transplanted cells release molecular signals that stimulate the surrounding tissue to heal. These signals can recruit the body’s own stem cells, reduce inflammation, and encourage new blood vessel growth at a damaged site. In practice, many cell therapies rely on a combination of all three mechanisms at once.
Autologous vs. Allogeneic: Your Cells or a Donor’s
Cell therapies split into two broad categories based on where the cells come from. Autologous therapies use your own cells, collected, processed or modified, then returned to your body. Because they’re your cells, the risk of rejection is essentially zero, there’s no need for immune-suppressing drugs afterward, and immune recovery tends to be faster. Treatment-related mortality is under 5% in most studies. The downside: if you have cancer, your own harvested cells could be contaminated with tumor cells that contribute to relapse.
Allogeneic therapies use cells from a donor. The advantage here is a tumor-free graft, plus donor immune cells can mount their own attack against remaining cancer, an effect called graft-versus-malignancy. Relapse rates are generally lower. The tradeoff is a higher risk of serious complications. Donor immune cells can attack the recipient’s healthy tissue (graft-versus-host disease), immune recovery takes longer, and infections are more common. Mortality risk rises further when the donor isn’t a close genetic match.
CAR-T Therapy for Blood Cancers
The type of cell therapy that has generated the most attention in recent years is CAR-T, in which a patient’s own immune cells are genetically engineered to recognize and destroy cancer. The process starts with a blood draw. T cells are separated out and sent to a manufacturing lab, where they’re modified to produce chimeric antigen receptors (CARs) on their surface. These receptors act like a lock-and-key system, letting the T cells latch onto specific proteins found on cancer cells. The modified cells are then grown until there are hundreds of millions of them and infused back into the patient. The entire process, from initial blood collection to infusion, takes roughly three to five weeks.
CAR-T therapies are currently approved for several blood cancers: acute lymphoblastic leukemia (ALL) in both children and adults, multiple myeloma, non-Hodgkin lymphoma (including large B-cell lymphoma, follicular lymphoma, and mantle cell lymphoma), and chronic lymphocytic leukemia. Seven distinct CAR-T products are on the market, each targeting slightly different cancer types or patient populations.
Side Effects of CAR-T
CAR-T therapy can cause serious, sometimes life-threatening side effects. The most common is cytokine release syndrome (CRS), an overwhelming inflammatory response that has been reported in up to 100% of patients in some clinical trials. Mild CRS looks like a high fever. More severe cases involve dangerous drops in blood pressure and difficulty breathing that require intensive care. A second major risk is neurotoxicity, which occurs in up to 67% of leukemia patients and 62% of lymphoma patients. Early signs include difficulty speaking, tremors, and trouble writing. In severe cases, symptoms can progress to seizures, confusion, or coma. One large analysis of over 1,000 patients found that 7% died from treatment-related causes within 30 days of receiving CAR-T cells.
Stem Cell Transplants
Hematopoietic stem cell transplantation, commonly known as a bone marrow transplant, is the oldest and most established form of cell therapy. It replaces the blood-forming stem cells in your bone marrow, which makes it useful for a surprisingly wide range of diseases. On the cancer side, it treats multiple myeloma, Hodgkin and non-Hodgkin lymphoma, acute and chronic leukemias, and myelodysplastic syndromes. But it also treats non-cancerous conditions: sickle cell disease, thalassemia, severe combined immune deficiency, aplastic anemia, and several rare genetic disorders.
More recently, stem cell transplants have been used for certain autoimmune diseases. Patients with severe systemic sclerosis, lupus, and relapsing-remitting multiple sclerosis have been treated with the approach, which essentially reboots the immune system by replacing the faulty one entirely.
Cell Therapy Beyond Cancer
One of the most notable non-cancer approvals came in 2023, when the FDA cleared the first cellular therapy for Type 1 diabetes. The treatment consists of donor pancreatic islet cells, the clusters responsible for producing insulin, infused into patients who experience dangerous, repeated episodes of severe low blood sugar despite intensive management. In clinical studies of 30 participants, 21 were able to stop taking insulin for at least a year. Ten of those participants remained insulin-free for more than five years. Five participants never achieved insulin independence at all.
Other approved cell therapies address tissue repair directly. One product uses a patient’s own cartilage cells, grown on a membrane, to repair knee cartilage damage. Another uses lab-grown skin cells to treat deep burns. An engineered blood vessel product and a thymus tissue transplant for children born without a functioning immune system are also on the list. These products illustrate how far cell therapy extends beyond the cancer and blood disease space.
Cost and Access
Cell therapy is among the most expensive medical treatment available today. CAR-T therapies alone range from roughly $174,000 to $600,000 for the product itself, and the drug price accounts for about 75% of the total bill. Hospitalization adds an average of $34,000, and managing side effects costs another $47,000 on average. For a single course of treatment, total costs can easily exceed half a million dollars.
These prices create real barriers. Insurance coverage varies, and even when payers approve treatment, the upfront costs strain hospital budgets since facilities often have to pay manufacturers before reimbursement arrives. There are ongoing concerns about whether healthcare systems in any country can sustain these costs at scale, particularly as approvals expand to more cancer types and larger patient populations.
Why Solid Tumors Remain Difficult
Nearly all approved CAR-T therapies target blood cancers, and solid tumors (breast, lung, colon, and similar cancers) remain a major challenge. The obstacles are specific and stubborn. Engineered T cells struggle to physically reach tumors buried deep in tissue, unlike blood cancers where the targets are circulating and accessible. Even when T cells arrive, solid tumors create a hostile local environment that suppresses immune cell activity, essentially putting the brakes on the very cells designed to kill the cancer. Tumors also evolve to shed or change the surface proteins that CAR-T cells are programmed to recognize, allowing cancer cells to escape detection.
Researchers are working on strategies that use synthetic biology to help T cells overcome these barriers, including engineering cells that can target multiple proteins at once and reprogram the tumor’s suppressive environment from the inside. Clinical trials in advanced solid tumors have shown early signs of progress, but no CAR-T product for solid tumors has reached FDA approval yet.