WT1 Peptide Vaccine Demonstrates Immune Activity in Pediatric High-Grade Gliomas

Clinical Summary:

• Design/Population: A phase 1/2 study evaluated an intradermal Wilms’ tumor gene 1 (WT1) peptide vaccine in pediatric patients with diffuse intrinsic pontine glioma, glioblastoma, or anaplastic astrocytoma.
• Key Outcomes: Although the study did not meet its primary efficacy end point, the vaccine was well tolerated and WT1-specific immune responses were associated with improved overall survival.
• Clinical Relevance: These findings support continued investigation of WT1-targeted immunotherapy, particularly in patients who develop vaccine-induced immune responses.

Results from a phase 1/2 study demonstrated that a Wilms' tumor gene 1 (WT1) peptide vaccine is well tolerated and elicited immune responses associated with improved survival among pediatric patients with high-grade gliomas. 

In this study, 18 patients younger than 20 years of age with diffuse intrinsic pontine glioma (n = 11), glioblastoma (n = 5), or anaplastic astrocytoma (n = 2) received intradermal WT1 peptide vaccine injections. The primary end point was the 9-month overall survival (OS) rate. Secondary analyses evaluated WT1-specific immune responses, including delayed-type hypersensitivity (DTH) and cytotoxic T-lymphocyte (CTL) frequency.

In the phase 1 portion of the study, 3.5 mg was established as the recommended dose for phase 2 after no dose-limiting toxicities were observed. 

At analysis, the 9-month OS rate was 44.4% in the overall population (90% confidence interval [CI], 24.4 to 65.9) and 27.3% in patients with diffuse intrinsic pontine glioma (90% CI, 7.9 to 56.4). The study did not meet its primary efficacy end point because the lower bound of the 90% CI for the diffuse intrinsic pontine glioma cohort did not exceed the prespecified threshold of 20%. 

Median OS was 5.4 months in patients with diffuse intrinsic pontine glioma. Among all patients, those who developed WT1-specific immune responses, defined by increased CTL frequency or count and/or positive DTH responses, experienced significantly longer median OS than nonresponders (9.9 vs 4.9 months; P = .024).

Injection-site reactions were the most frequently reported treatment-related adverse event, occurring in 77.8% of patients. No dose-limiting toxicities were observed.

“The vaccine was not effective statistically but was well tolerated and appeared to have induced WT1-specific immune responses,” concluded Dr Hashii et al. These results suggest “improved survival in WT1-specific immune responders among [diffuse intrinsic pontine glioma] patients and warrant its further development.”  

Source:

Hashii Y, Fujisaki H, Terashima K, et al. Phase 1/2 study of a WT1 peptide-dosing emulsion in pediatric patients with recurrent/refractory diffuse intrinsic pontine glioma, glioblastoma, or anaplastic astrocytoma. Eur J Cancer. Published online: May 18, 2026. doi:10.1016/j.ejca.2026.116808