In Spain, between 1,300 and 1,500 children are diagnosed with cancer each year, according to the Registro Español de Tumores Infantiles (RETI‑SEHOP official registry). Among the rare cancers that affect youngsters, brain tumors are especially lethal, representing roughly 20 % of novel diagnoses and an annual incidence of about five cases per 100,000 children. Despite advances in imaging and therapy, the outlook for many pediatric central‑nervous‑system (CNS) tumors remains grim.
Researchers at the Cancer Center Clínica Universidad de Navarra (CUN) are preparing a phase‑2 clinical trial that could change that picture. Led by Dr. Jaime Gállego, coordinator of the CNS tumor area at CUN, the team plans to test a genetically engineered adenovirus serotype 5—the same virus that causes the common cold—as an oncolytic agent against three of the most aggressive pediatric brain cancers.
The virus has been re‑engineered for two key purposes. First, it replicates only in tumor cells that carry specific genetic alterations, sparing healthy tissue. Second, the modifications increase the virus’s affinity for tumor‑cell membranes, improving its ability to infect and destroy malignant cells while leaving normal brain tissue largely untouched.
Trial design and target tumors
The upcoming study builds on a 2022 The New England Journal of Medicine report that demonstrated the feasibility and safety of an oncolytic virus in children with diffuse intrinsic pontine glioma. In phase 2, the same engineered virus will be tested against three pediatric CNS tumor groups: high‑grade gliomas, embryonal tumors such as medulloblastoma and atypical teratoid/rhabdoid tumor and ependymomas. All three have shown promising responses in animal models.
Enrollment will start with five patients per tumor type, aged 1 to 25 years. If any of the initial five show a clear clinical benefit—either disease stabilization or measurable tumor reduction—the cohort can expand to up to 13 patients, for a potential total of 39 participants.
Unlike the earlier phase‑1 trial, which enrolled children whose disease had progressed after standard therapy, this phase 2 cohort will consist of newly diagnosed patients. The protocol calls for a stereotactic injection: a thin cannula delivers the diluted virus directly into the tumor under three‑dimensional neuronavigation, ensuring the needle path avoids functional brain areas. Pre‑procedure magnetic‑resonance imaging will map the tumor and surrounding anatomy in detail.
Safety profile and next steps
In the phase‑1 study of 12 children, investigators reported no major toxicity and observed signs of efficacy, including longer-than‑expected survival. “No significant toxicity was observed,” Dr. Gállego noted, adding that the upcoming trial will confirm safety and assess true therapeutic impact.
Systemic delivery is not an option because the immune system would clear the virus within minutes. The team therefore injects the virus locally, where it can replicate within tumor cells before the immune response is triggered.
Future iterations aim to add a further genetic edit that would boost the virus’s ability to stimulate an anti‑tumor immune response—what the researcher describes as “flipping the immune‑system switch.” The trial will remain on hold until the European Medicines Agency (EMA) grants approval; once started, the study is expected to run for about three years, though recruitment may shorten that timeline.
Funding and broader implications
The Spanish Association Against Cancer (AECC) is contributing €1 million through its 2025 Clinical Studies Grant to support the phase‑2 trial. “Effective treatments are urgently needed,” said AECC scientific director Marta Puyol, emphasizing the importance of pediatric‑first trials rather than adapting adult studies for children.
Beyond this specific virus, the effort reflects a growing global interest in oncolytic virotherapy—a strategy that uses engineered viruses to both lyse cancer cells and prime the immune system. If successful, the trial could pave the way for similar approaches in other hard‑to‑treat pediatric cancers.
| Tumor type | Initial cohort | Potential maximum |
|---|---|---|
| High‑grade glioma | 5 | 13 |
| Embryonal tumors (medulloblastoma, ATRT) | 5 | 13 |
| Ependymoma | 5 | 13 |
For families and clinicians seeking updates, the EMA’s public register will list the trial’s status once the application is submitted. The RETI‑SEHOP registry continues to monitor pediatric cancer incidence across Spain, providing essential epidemiological context for studies like this see here.
While the trial awaits regulatory clearance, the research team remains optimistic: “Families want a chance to fight,” Dr. Gállego said, “and we hope to give them that soon.”
Disclaimer: This article is for informational purposes only and does not constitute medical advice. Readers should consult qualified health professionals for diagnosis or treatment options.
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