A three-year-old boy with chemotherapy-resistant liver cancer has achieved complete remission after receiving an experimental form of CAR T-cell immunotherapy, offering researchers fresh evidence that specially engineered immune cells could eventually be used against difficult-to-treat solid tumours.

The child had advanced hepatoblastoma, a rare childhood liver cancer that had spread to other parts of his body and returned despite several rounds of chemotherapy and surgery.

Doctors treated him with two infusions of genetically modified CAR T cells designed to recognise a protein called glypican-3 (GPC3) on cancer cells. The experimental cells were additionally engineered to produce the immune-signalling proteins interleukin-15 (IL-15) and interleukin-21 (IL-21).

After the second infusion, scans showed complete resolution of the metastatic disease. According to the research team, the complete regression had continued for at least 12 months, and the child did not experience cytokine release syndrome, one of the serious complications associated with CAR T-cell treatment. New England Journal of Medicine

The case was reported by researchers from Baylor College of Medicine, Texas Children’s Hospital and Seattle Children’s Hospital in the New England Journal of Medicine.

The report, published online on 9 September 2026, describes a three-year-old boy whose hepatoblastoma had stopped responding to chemotherapy. The cancer had metastasised, including to the lungs, and had returned following previous treatment. New England Journal of Medicine

The researchers reported that after two CAR T-cell infusions, given eight weeks apart, imaging showed the disappearance of the metastatic cancer.

Importantly, this does not yet mean the child has been permanently cured. The published report documents complete regression lasting at least one year. Longer follow-up and results from additional patients will be needed to understand how durable the response really is.

Key points from the case

• Patient: 3-year-old boy
• Cancer: Hepatoblastoma
• Disease status: Metastatic and chemotherapy-resistant
• Experimental treatment: GPC3-targeted CAR T cells
• Additional engineering: IL-15 and IL-21
• Number of infusions: Two
• Interval between infusions: Eight weeks
• Response: Complete regression of metastatic disease
• Follow-up reported: At least 12 months
• Cytokine release syndrome: Not observed in this case
• Clinical trial: CARE, a Phase 1 study New England Journal of Medicine

What Is Hepatoblastoma?

Hepatoblastoma is the most common primary liver cancer in young children. It generally occurs in very young children and can require a combination of surgery, chemotherapy and other specialist treatments.

In this particular case, the disease was particularly difficult to treat because it had spread beyond the original liver tumour and subsequently returned despite previous treatment.

Baylor researchers said the child initially had a large primary liver tumour as well as metastatic disease in the lungs. Before entering the CARE study, he had received three lines of chemotherapy and undergone surgery to remove the primary liver tumour and two lung metastases. A new lung metastasis subsequently developed. Baylor College of Medicine

This left doctors facing a cancer that was no longer responding adequately to conventional chemotherapy.

How CAR T-Cell Therapy Works

CAR T-cell therapy is a form of cellular immunotherapy.

Rather than relying entirely on medicines to kill cancer cells, the approach uses the patient’s own immune cells and modifies them so they can recognise particular features of cancer.

The general process involves:

1. Collecting T cells from the patient’s blood.
2. Genetically modifying the T cells in a laboratory.
3. Giving the cells a special receptor known as a chimeric antigen receptor (CAR).
4. Expanding the modified cells so that a therapeutic number can be produced.
5. Returning the engineered cells to the patient.
6. Allowing the modified T cells to identify and attack cells carrying the target antigen.

The National Cancer Institute explains that CAR T cells have become an important treatment for several blood cancers, although their use against solid tumours remains experimental. National Cancer Institute

CAR T-cell therapy has produced major advances in some blood cancers. However, researchers have struggled to achieve the same results against solid tumours.

There are several reasons.

1. Finding the right target

A CAR T cell needs to recognise a particular protein or antigen.

The challenge is finding a target that is:

• abundant on cancer cells;
• present on as many tumour cells as possible;
• accessible to the engineered T cells; and
• largely absent from healthy tissues.

Targeting a protein that is also widely found on healthy cells could cause the immune system to damage normal organs.

2. The tumour environment can suppress immune cells

Solid tumours can create an environment that makes it difficult for immune cells to function effectively.

Researchers have described factors including immunosuppressive molecules, limited nutrients and other biological barriers that can prevent T cells from working efficiently. National Cancer Institute

3. Tumours are not always uniform

Cancer cells within the same tumour can differ from one another.

Some cells may have large amounts of a particular target antigen, while others may have little or none. This creates a potential escape route for cancer cells that CAR T cells cannot recognise.

For these reasons, developing CAR T-cell treatments for solid tumours has proved considerably more challenging than developing them for certain blood cancers. National Cancer Institute

Why Scientists Chose Glypican-3

The experimental therapy used in the CARE study was designed to recognise glypican-3, or GPC3.

GPC3 is a protein associated with several cancers, including hepatoblastoma and other solid tumours.

The researchers designed the CAR T cells so that they could recognise GPC3-positive cancer cells and attack them.

This approach is particularly interesting in childhood liver cancer because GPC3 can provide a target that helps distinguish malignant cells from many normal mature tissues.

The treatment is therefore not simply conventional CAR T therapy. The researchers have attempted to build additional functions into the cells to help them remain active in the hostile environment surrounding a solid tumour.

The CAR T Cells Were Given an Extra Immune Boost

One of the most interesting aspects of the experimental treatment is the addition of IL-15 and IL-21.

These are cytokines — signalling proteins involved in regulating immune-cell activity.

The researchers engineered the CAR T cells to produce both of these proteins.

The idea is to help the modified T cells:

• survive for longer;
• multiply more effectively;
• remain active around the tumour;
• strengthen their cancer-killing activity; and
• potentially overcome some of the limitations faced by conventional CAR T cells in solid tumours.

Previous laboratory research has investigated the use of IL-15 and IL-21 to strengthen T-cell-based cancer treatments. The NCI has reported experimental work showing that T cells equipped with both cytokines demonstrated stronger anti-tumour activity in laboratory and animal studies than cells carrying neither or only one of the cytokines. National Cancer Institute

The current child’s response provides an important human clinical observation, but it remains far too early to know how broadly the strategy will work.

Researchers Also Added a Safety Switch

The experimental cells contained another important feature: an inducible safety switch.

The researchers used an inducible caspase-9 system designed to allow the engineered cells to be eliminated with a specific drug if necessary.

This type of built-in control is being investigated as a way of improving the safety of genetically modified cell therapies.

The CARE study’s treatment design includes GPC3-targeted CAR T cells carrying IL-15 and IL-21 along with the safety-switch system. Baylor College of Medicine

Two Infusions Produced a Dramatic Response

The child received two infusions of his own engineered T cells, with the treatments separated by eight weeks.

The response developed in stages.

After the first treatment

Doctors observed a partial response, meaning the cancer burden decreased but had not completely disappeared.

After the second treatment

Following the second infusion, imaging showed complete resolution of the metastatic disease.

According to Baylor College of Medicine, the complete regression continued for one year after treatment. Baylor College of Medicine

The New England Journal of Medicine report similarly states that the child experienced complete regression lasting at least 12 months. New England Journal of Medicine

The Child Did Not Develop Cytokine Release Syndrome

One particularly notable feature of this case was the absence of cytokine release syndrome (CRS).

CRS is a potentially serious complication of CAR T-cell therapy. It occurs when activated immune cells release large quantities of cytokines, potentially causing symptoms ranging from fever and fatigue to low blood pressure and breathing difficulties.

Severe CRS can be life-threatening. National Cancer Institute

The National Cancer Institute also identifies neurological complications, collectively known as immune effector cell-associated neurotoxicity syndrome (ICANS), as another possible concern with CAR T-cell treatment. National Cancer Institute

In the reported case, however, the researchers found no dose-limiting toxicities or CRS. The treatment was administered in the outpatient setting. Baylor College of Medicine

That is an important finding, although one patient’s experience cannot establish that the treatment will be equally safe for other children.

The CARE Trial Will Test the Treatment in More Patients

Perhaps the most important next step is determining whether this result can be reproduced.

The child is participating in the CARE study, officially registered as NCT04715191.

It is a Phase 1 clinical trial investigating IL-15- and IL-21-armoured GPC3-specific CAR T cells in children with GPC3-positive solid tumours.

The study includes several childhood cancers, including liver cancer, rhabdomyosarcoma, malignant rhabdoid tumour, liposarcoma, Wilms tumour and yolk sac tumour. Clinical Trials

The study is designed primarily to investigate the treatment’s safety, dosing and early signs of effectiveness rather than to prove that the therapy is a definitive cure.

Why a larger study matters

A single patient can produce an extraordinary medical result, but researchers need to treat such findings cautiously.

Future patients will help scientists determine:

• How often complete responses occur.
• How long responses last.
• Which cancers respond best.
• Whether GPC3 levels influence treatment success.
• How well the engineered cells survive in the body.
• Whether serious side effects appear in a larger group.
• Whether the treatment can work against other GPC3-positive solid tumours.

The significance of the report goes beyond hepatoblastoma.

Researchers around the world are trying to adapt CAR T-cell therapy for solid tumours, including cancers of the brain, pancreas, breast, lung and other organs.

The central challenge is getting engineered immune cells to locate the tumour, enter it, survive there and continue attacking cancer cells without causing unacceptable damage to healthy tissue.

The NCI describes these obstacles as major reasons why CAR T-cell development for solid tumours has lagged behind progress in blood cancers. National Cancer Institute

The new CARE approach attempts to address several of these problems simultaneously:

Target recognition
→ GPC3 directs the CAR T cells towards certain cancer cells.

Immune-cell support
→ IL-15 and IL-21 are intended to strengthen the engineered T cells.

Safety control
→ An inducible safety switch provides researchers with a mechanism to eliminate the cells if necessary.

This combination represents an example of how scientists are attempting to make the next generation of CAR T-cell therapies more sophisticated.

A Promising Result — But Not Yet a Cure

The child’s story is undoubtedly encouraging, but the scientific findings need to be placed in context.

This was one patient in an early-stage clinical trial.

The study does not yet establish that the therapy will cure hepatoblastoma or other solid cancers. Nor does it show that the treatment will work for every child with metastatic liver cancer.

The fact that the cancer remained in complete regression for at least 12 months is an important early result, but longer follow-up will be necessary.

The wider CARE trial will provide much more information about the treatment’s safety, effectiveness and durability.

As with other experimental cancer treatments, patients should only consider such therapies through appropriate specialist care and clinical-trial processes.

Why This Research Matters

For decades, CAR T-cell therapy has been developed primarily around cancers of the blood and immune system.

Solid tumours have presented a much harder problem.

The response seen in this three-year-old boy suggests that a carefully engineered CAR T-cell design may be able to overcome at least some of the barriers that have limited the technology in solid cancers.

Researchers are particularly interested in whether combining:

• a carefully selected tumour target;
• additional immune-stimulating signals;
• improved CAR T-cell persistence; and
• controllable safety mechanisms

can produce stronger and longer-lasting responses.

The latest case provides an early human example of that strategy.

Frequently Asked Questions

What type of cancer did the three-year-old boy have?

He had hepatoblastoma, a childhood liver cancer that had spread beyond the liver and had become resistant to chemotherapy. Baylor College of Medicine

What treatment did he receive?

He received two infusions of experimental GPC3-specific CAR T cells engineered to express IL-15 and IL-21. New England Journal of Medicine

Is he considered cured?

The published report documents complete regression lasting at least 12 months. It is too early to describe the result as a permanent cure because longer follow-up is required. New England Journal of Medicine

Is CAR T-cell therapy already available for solid tumours?

CAR T-cell therapy is an established treatment for some blood cancers, but its use for solid tumours remains experimental. National Cancer Institute

Did the child experience serious CAR T side effects?

According to the researchers, he did not experience dose-limiting toxicity or cytokine release syndrome during the reported treatment. Baylor College of Medicine

Will other children receive the experimental treatment?

The CARE Phase 1 clinical trial is evaluating the treatment in children with GPC3-positive solid tumours. Clinical Trials

Final Thoughts

The complete disappearance of detectable metastatic disease in a young child with chemotherapy-resistant hepatoblastoma represents an important early finding in the search for new cancer treatments.

The most significant part of the story may not simply be that CAR T cells were able to attack the cancer. It is that researchers have developed cells with multiple engineered functions — tumour recognition through GPC3, additional immune stimulation through IL-15 and IL-21, and an incorporated safety mechanism.

For now, the result should be viewed as promising early clinical evidence rather than proof of a cure.

The next stage is much larger and more difficult: treating additional patients and finding out whether the same response can be achieved consistently and safely.

If those results are positive, this research could add to growing efforts to bring CAR T-cell therapy beyond blood cancers and towards some of the solid tumours that have remained difficult to treat.

References and Further Reading

• New England Journal of Medicine — Complete Regression of Hepatoblastoma after IL-15 and IL-21 CAR T-Cell Therapy New England Journal of Medicine
• Baylor College of Medicine — CARE Study Reports Complete Regression of Liver Cancer in a Child Baylor College of Medicine
• ClinicalTrials.gov — CARE Study NCT04715191 Clinical Trials
• National Cancer Institute — CAR T Cells: Engineering Immune Cells to Treat Cancer National Cancer Institute
• National Cancer Institute — T-Cell Transfer Therapy National Cancer Institute

Image sources: The visual references above include educational material from the National Cancer Institute and St. Jude Children’s Research Hospital, alongside medical illustration searches relating to CAR T-cell therapy and hepatoblastoma.