Experimental IDH1 Vaccine Shows Encouraging 8-Year Survival in IDH-Mutant Astrocytoma

High-grade astrocytomas are among the most aggressive brain tumours and remain difficult to cure despite surgery, radiotherapy, and chemotherapy. A major proportion of these tumours harbour the IDH1-R132H mutation, an early and stable genetic alteration that drives tumour growth while creating a tumour-specific neoepitope recognizable by the immune system. This makes it an attractive target for immunotherapy.

Researchers from the German Cancer Research Centre (DKFZ), Mannheim University Medical Centre, Heidelberg University Hospital, and collaborating institutions reported the final long-term results of the multicentre NOA16 Phase 1 trial (NCT02454634) in Nature Cancer.

The open-label study enrolled 33 patients with newly diagnosed IDH1-R132H-positive grade III and IV astrocytomas who received standard treatment including surgery, radiotherapy, and/or temozolomide chemotherapy followed by eight doses of the investigational IDH1-vac peptide vaccine over approximately six months. The primary objective was to evaluate safety and vaccine-induced immune responses, while long-term clinical outcomes were assessed as secondary endpoints. Patients were followed for a median of 99.8 months, providing one of the longest follow-up datasets reported for an investigational glioma vaccine.

Encouraging Eight-Year Survival

After up to eight years of follow-up, vaccinated patients demonstrated encouraging long-term outcomes.

Overall, the 8-year progression-free survival (PFS) rate was 42% (95% CI, 24%–59%), while the 8-year overall survival (OS) rate reached 66% (95% CI, 46%–79%). Median overall survival for the overall study population had not yet been reached after eight years of follow-up, reflecting the durability of survival observed in the cohort.

Among patients with grade IV astrocytoma, median overall survival was 106.1 months, substantially longer than the 31.6–56.4 months typically reported in historical studies. Patients whose tumours were completely removed surgically experienced the most favourable outcomes, with 8-year PFS and OS rates of 68% and 88%, respectively, while median overall survival had not yet been reached after eight years. The investigators also highlighted complete surgical resection as an important prognostic factor associated with improved long-term outcomes.

Durable Immune Responses Linked to Better Outcomes

The vaccine successfully stimulated both T-cell and B-cell immune responses against the mutant IDH1 protein. Vaccine-induced T-cell responses developed in 87.5% of participants, antibody responses in 93.8%, and both immune responses in 81.3% of patients.

Patients who developed sustained antibody responses experienced significantly better long-term clinical outcomes than those with weaker or earlier antibody responses, suggesting that durable humoral immunity may contribute to prolonged disease control. In contrast, the magnitude of vaccine-induced T-cell responses alone was not clearly associated with improved long-term survival, highlighting the potential importance of sustained B-cell immunity.

Researchers also demonstrated that vaccine-induced T cells migrated into tumour tissue. These mutation-specific T cells were detected in inflammatory lesions associated with pseudoprogression, but not in patients with true early disease progression, providing evidence that the immune response was reaching the tumour itself.

Booster Vaccination Shows Potential

Long-term immune monitoring suggested that additional booster vaccinations administered years after the initial treatment could successfully restore immune responses without introducing new safety concerns. Although evaluated in only a small number of patients, these findings indicate that booster doses may help maintain long-term protection and warrant further investigation.

Safety and Study Limitations

The NOA16 trial previously met its primary safety endpoint, and no new significant safety signals were observed during long-term follow-up or after booster vaccinations.

However, the investigators emphasize that this was a single-arm Phase 1 study involving only 33 participants and lacked a randomized control group. Consequently, although survival outcomes compare favourably with historical data, definitive conclusions regarding clinical efficacy cannot yet be drawn.

The researchers also performed a retrospective molecular analysis of available tumour samples, which suggested more favourable outcomes among patients with lower-grade methylation profiles. However, they noted that the small sample size limits interpretation of these exploratory findings.

Clinical Implications

Lead author Lukas Bunse explained that the IDH1-R132H mutation appears early in tumour development and remains stable throughout disease progression, making it an ideal target for vaccine-based immunotherapy.

Senior investigator Michael Platten noted that this study provides the first evidence that vaccination against a shared tumour-driving mutation may be associated with long-term survival benefits in brain tumours. He added that these encouraging findings have paved the way for a multicentre, randomized Phase 2 trial.

What This Means and What Comes Next?

The NOA16 study represents an important step toward developing off-the-shelf precision cancer vaccines for patients with IDH-mutant astrocytomas. Unlike personalized neoantigen vaccines, IDH1-vac targets a shared clonal driver mutation found in many patients, making it suitable for broader clinical use while avoiding the need for individualized vaccine manufacturing.

Future studies will evaluate whether combining the vaccine with immune checkpoint inhibitors or IDH inhibitors can further improve outcomes.

While these results should be interpreted cautiously because of the study design, the durable survival, robust immune activation, and favourable safety profile provide a strong rationale for the ongoing randomized Phase 2 trial to determine whether IDH1-vac can become part of standard treatment for newly diagnosed IDH-mutant astrocytoma.

Reference

Vaccine Against Brain Tumors Shows Promising Long-Term Results – German Cancer Research Center

IDH1-mutant vaccine in newly diagnosed astrocytoma: final analysis of the multicenter, single-arm, open-label, first-in-human phase 1 NOA16 trial | Nature Cancer