# Simultaneous Radiotherapy with PD-1 and IDO1 Blockade for Overcoming Immune Suppression in Glioblastoma

> **NIH NIH P50** · NORTHWESTERN UNIVERSITY · 2020 · $342,946

## Abstract

PROJECT 2: SUMMARY
Immunotherapy carries great promise for the treatment of several solid tumors, including malignant glioma.
But in order to have a true impact in the disease course, a combinatorial strategy is likely required. In
particular in glioblastoma, a heterogeneous disease characterized by local immunosuppression and an
immune-privileged environment as well as increased vascularity, a combination of radiotherapy with
concomitant immunomodulation by both a checkpoint inhibitor and IDO inhibitor could prove effective. In a
series of preclinical experiments, we have shown that the triple combination of radiotherapy, checkpoint
inhibition and IDO inhibition exert enhanced antitumor activity. Strikingly, this triple therapy led to a durable
survival benefit in mice with large, intracranial GBM. We confirmed that this approach inhibited
immunosuppressive IDO1 metabolism, as determined by an increase of intratumoral tryptophan and a
decrease of kynurenine levels. These preclinical findings are now to be translated within a clinical trial to
patients suffering from newly diagnosed GBM. The innovation of this trial is enhanced by the incorporation of
α-[11C]-methyl-L-Trp (AMT)-PET imaging, which is a noninvasive method to quantify tryptophan uptake and/or
IDO1 enzyme activity, and a comprehensive immunmonitoring panel. AMT-PET imaging therefore facilitates
the real-time evaluation of intracranial IDO1 enzyme inhibition, which is advantageous to patients with tumors
that are not conveniently accessible for repeat tissue sampling. The clinical trial will include correlative
analysis of systemic and intratumoral immunological markers, tumor gene expression and mutagenic burden,
quantitative AMT-PET data, and treatment outcome (overall survival as primary endpoint). In parallel, we will
conduct further experiments with mice reconstituted with human immune systems and inoculated with tumors
of human origin (PDX). This will allow for testing hypotheses arising from the clinical experience, as well as
additional therapeutics that could be incorporated in future clinical trials that are derivative of that being tested
in patients here. Ultimately, our research will influence future immunotherapeutic strategies in the
multimodality management of patients with glioma.

## Key facts

- **NIH application ID:** 9981698
- **Project number:** 5P50CA221747-03
- **Recipient organization:** NORTHWESTERN UNIVERSITY
- **Principal Investigator:** Derek Alan Wainwright
- **Activity code:** P50 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $342,946
- **Award type:** 5
- **Project period:** — → —

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9981698

## Citation

> US National Institutes of Health, RePORTER application 9981698, Simultaneous Radiotherapy with PD-1 and IDO1 Blockade for Overcoming Immune Suppression in Glioblastoma (5P50CA221747-03). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9981698. Licensed CC0.

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