She had exhausted every available treatment and was ineligible for trials.
In Heidelberg, Germany, a seventeen-year-old with metastatic kidney cancer and no remaining treatment options received an experimental cell therapy targeting a protein called PRAME — and entered remission. The case, reported in April 2026, represents the first known use of this approach in a pediatric patient, and the response has held at six months. It does not yet rewrite the rules of cancer medicine, but it reminds us that the boundary between the exhausted and the possible is rarely as fixed as it appears.
- A teenager with tumors in her lungs, liver, and brain had been turned away from clinical trials and had no standard treatments left — her situation was, by every conventional measure, terminal.
- A single infusion of engineered T cells targeting the PRAME protein produced tumor regression across all sites within three months, with liquid biopsy confirming molecular remission — an outcome that surprised even her own physicians.
- The immune system's forceful response triggered cytokine release syndrome, a serious but manageable inflammatory reaction that required anti-inflammatory drugs and corticosteroids before resolving.
- At six months, the remission is holding and the patient is in excellent physical condition — a result the company's chief medical officer called remarkable in a disease context where such words carry real weight.
- Immatics is now planning a first-in-pediatrics Phase 1/2 trial at Heidelberg, moving from a single extraordinary case toward the structured evidence needed to determine whether this can help other children.
A seventeen-year-old in Heidelberg had reached the end of the road. Her kidney cancer had spread to the lungs, liver, and brain, an abdominal tumor had grown to sixteen centimeters, and she had been turned away from clinical trials. Her treating physician, Dr. Christian M. Seitz, made an unusual request: compassionate access to an experimental therapy from biotech company Immatics that had never been used in a child before.
The therapy works by engineering a patient's own T cells to recognize PRAME, a protein expressed on the surface of more than fifty cancer types and found at particularly high levels in childhood tumors. The specific version used, IMA203CD8, was manufactured at the Hopp Children's Cancer Center where the patient was being treated.
Three months after the infusion, imaging showed marked regression across every tumor site. A liquid biopsy — which detects cancer DNA circulating in the blood — came back negative, indicating molecular remission. At six months, the response was still holding. The one significant complication, cytokine release syndrome, was managed with anti-inflammatory medications and resolved without lasting harm.
Dr. Seitz expressed careful gratitude, crediting Immatics and calling for further clinical evaluation. Cedrik Britten, the company's chief medical officer, described the outcome as remarkable — language that carries particular weight in pediatric oncology, where advanced disease leaves little room for optimism.
Immatics is now planning a Phase 1/2 basket study at Heidelberg to evaluate the therapy in children and adolescents with relapsed or refractory PRAME-expressing solid tumors. One case is not yet a new standard of care, but in a field where proof of concept can redirect years of research, this single remission may matter far beyond one patient's survival.
A seventeen-year-old patient in Heidelberg, Germany, had run out of options. The kidney cancer spreading through her body—metastases in the lungs, liver, and brain, with an abdominal tumor measuring sixteen centimeters across—had progressed despite every available treatment. She was ineligible for clinical trials. Her doctors had exhausted the standard arsenal. In that position, with nothing left to lose, her treating physician made an unusual request: access to an experimental cell therapy that had never been tried in a pediatric patient before.
The therapy came from Immatics, a biotech company focused on targeting a protein called PRAME, which appears on the surface of more than fifty different cancers and shows particularly high expression in childhood tumors. The approach works by engineering a patient's own T cells—the immune system's frontline soldiers—to recognize and attack cancer cells displaying PRAME. The specific version used here, encoded by a vector called IMA203CD8, was manufactured at the Hopp Children's Cancer Center in Heidelberg, where the patient was being treated.
What happened next surprised even the physicians involved. Three months after the infusion, imaging showed remission. The tumors across all sites—liver, lungs, brain—had regressed markedly. Liquid biopsy testing, which detects tumor DNA circulating in the bloodstream, came back negative, indicating molecular remission. At six months of follow-up, the response was still holding. The patient was in excellent physical condition. The only significant adverse event was cytokine release syndrome, a known side effect of cell therapies in which the immune system's activation causes inflammation; it was manageable and resolved with anti-inflammatory medications and corticosteroids.
Dr. Christian M. Seitz, the treating physician and group leader of the translational immunotherapy team at Heidelberg, described the moment with careful gratitude. He credited Immatics for providing the therapy and expressed hope that further clinical evaluation might demonstrate the potential of PRAME-targeted approaches in other children and adolescents facing similar diagnoses. Cedrik Britten, Immatics' chief medical officer, called the response remarkable and deeply encouraging—language that signals how unusual this outcome is in the context of advanced pediatric cancer, where options are few and prognosis is often grim.
The case matters because it opens a door. PRAME appears across multiple pediatric solid tumors, and young patients often mount particularly strong immune responses. The company is now planning a first-in-pediatrics Phase 1/2 basket study at the Heidelberg center, designed to evaluate the therapy in children and adolescents with relapsed or refractory PRAME-expressing solid tumors. Immatics is also running parallel trials in adults with melanoma and other cancers, testing both this second-generation cell therapy and a bispecific antibody approach targeting the same protein.
What remains to be seen is whether this single case—dramatic as it is—can be replicated in a broader population. One patient achieving remission after exhausting all other options is not yet proof of a new standard of care. But it is proof of concept, and in pediatric oncology, where the disease landscape is sparse and the stakes are absolute, proof of concept can shift the entire trajectory of research and hope.
Notable Quotes
We are very grateful to Immatics for providing the PRAME-directed TCR that enabled us to reprogram the pediatric patient's cells. We hope that possible further clinical evaluation may demonstrate the potential of PRAME-targeted cellular immunotherapies in helping other children and adolescents with cancer.— Dr. Christian M. Seitz, treating physician at Hopp Children's Cancer Center Heidelberg
Seeing such a profound response in a pediatric patient who had no treatment options left is both remarkable and deeply encouraging. It reinforces our belief in PRAME as a powerful target and highlights the potential of cell therapy for pediatric cancers.— Dr. Cedrik Britten, Chief Medical Officer at Immatics
The Hearth Conversation Another angle on the story
Why does this one case matter so much? It's a single patient.
Because she had nothing left. Every standard treatment had failed. She was ineligible for trials. In that position, a single response—especially one that holds at six months—tells you the mechanism might actually work. It's permission to keep going.
What makes PRAME special compared to other cancer targets?
It shows up in over fifty different cancers, and it's particularly abundant in childhood tumors. Most targets are specific to one or two cancer types. PRAME is everywhere in pediatric disease, which means if this works, it could apply broadly.
The cytokine release syndrome—that sounds serious.
It is, but it's also manageable and expected with cell therapies. What matters here is that it resolved. The patient is in excellent condition at six months. That's the real signal.
So what happens now?
They're planning a larger pediatric study at the same center in Heidelberg. If this replicates—if other kids with relapsed or refractory tumors respond the way this patient did—then you're looking at a genuinely new treatment option for diseases that have very few.
Is there a risk this was just luck?
Always. One case is anecdotal. But in pediatric oncology, you don't have the luxury of waiting for perfect data when children are dying. This case gives them enough signal to test the hypothesis properly.