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DKFZ IDH-mutant glioma peptide / neoantigen vaccine update

IDH1R132H peptide vaccine — the DKFZ-led neoantigen IO program for IDH-mutant glioma, extending NOA-16 toward combination and post-vorasidenib positioning.

  • Speaker(s): Michael Platten, MD; Felix Sahm, MD, PhD; aligned with the Ton N. Schumacher (NKI) and DKFZ Neuro-Oncology team
  • Affiliation: DKFZ / Heidelberg University Hospital (Department of Neurology + Neuropathology)
  • Anchor type: targeted therapy / trial (neoantigen vaccine)
  • Day / session: Day 1 (Mon Mar 23, 2026), IDH-mutant Glioma session
  • Status: post-meeting; details captured from AACR Brain 26 program notes, the NOA-16 Nature 2021 first-in-human report (Platten et al.), and DKFZ follow-up; expanded 2026 cohort numerics and any vaccine + checkpoint combination data TBD pending abstract supplement

Headline finding

Updated cohort and follow-on data from the DKFZ IDH1R132H peptide vaccine program — the most-watched neoantigen-IO + IDH-mut combination strategy. NOA-16 (Nature 2021) established that the IDH1R132H peptide is genuinely immunogenic and produces mutation-specific CD4 T-cell responses with a tolerable safety profile in newly-diagnosed grade 3/4 IDH-mut glioma. The Brain 26 readout extends cohort N and brings vaccine + checkpoint (PD-1/PD-L1) combination signals into view, plus the practical question of how to sequence with vorasidenib. Specific PFS, immune-response rate, and combo-cohort numbers TBD.

Mechanism / methodology

The vaccine is a long-peptide formulation of the IDH1R132H neoepitope, presented through HLA-DR class II to drive a tumor-selective CD4 T-cell response (the IDH1R132H mutation is a shared, truncal driver, making it a near-universal target across IDH-mut glioma). Combination arms layer PD-1 or PD-L1 blockade on top of vaccination to overcome the strongly immunosuppressive D-2-HG-driven TME — a logic that intersects with vorasidenib's ability to lower 2-HG and potentially "open" the TME for IO.

Mechanism / methodology deep dive

Underlying biology. The IDH1R132H point mutation creates a tumor-restricted neoepitope spanning the mutated arginine-to-histidine residue, presented promiscuously on multiple HLA class II alleles (notably HLA-DR1 / DRB1 broadly) — making it one of the few truly "off-the-shelf" shared neoantigens across IDH-mut glioma. The mutation is truncal (present in essentially all tumor cells), and homozygous expression on all malignant clones makes immune editing / antigen loss biologically constrained — losing IDH-mut would also lose the oncogenic driver.

Therapeutic design. A 20-mer synthetic long peptide spanning the IDH1R132H mutation (NOA-16 construct: p123–142 IDH1(R132H)), formulated with Montanide ISA-51 adjuvant and topical imiquimod (TLR7 agonist) at the injection site to drive class-II–restricted CD4 helper responses. Subcutaneous prime-boost schedule; combination arms add anti-PD-L1 (avelumab/atezolizumab-class) per the public NOA-16 and follow-on protocols. Specific 2026 combination cohort schedule TBD.

Resistance / failure modes. Documented: pseudoprogression (vaccine-driven immune infiltrate mimicking tumor growth on MRI) requiring careful Rx-response distinction; modest durability of peripheral T-cell responses without boost. Anticipated escape: HLA class II downregulation on tumor cells; D-2-HG–driven local immunosuppression limiting effector trafficking; outgrowth of IDH-mut–retaining but antigen-presentation-defective subclones.

Translational gaps. Optimal sequencing with vorasidenib (does 2-HG suppression enhance or reduce neoepitope presentation?), durability of response, and whether a class I–restricted booster could add CD8 effector activity remain undefined.

Where it fits in the corpus

  • AACR 2026: IDH-mut and neoantigen-vaccine sessions in San Diego pick up the same thread.
  • SITC 2026: the Cathy Wu Smalley Lecture on neoantigen vaccines is the broader frame; IDH1R132H is one of the cleanest shared-neoantigen examples.
  • Related Brain 26 entries: vorasidenib-post-indigo.md, suva-glioma-cell-states.md.

Open questions

  • Does vorasidenib (2-HG suppression) genuinely improve the immune microenvironment enough to amplify vaccine response, or does it paradoxically reduce neoepitope presentation by de-differentiating less?
  • Long-term durability of IDH1R132H-specific T-cell responses and whether boosting / heterologous prime-boost extends them remains an open question.