Targeting Treg cells with GITR activation alleviates resistance to immunotherapy in murine glioblastomas

Immune checkpoint blockers (ICBs) have failed in all phase III glioblastoma (GBM) trials. Here, we show that regulatory T (Treg) cells play a key role in GBM resistance to ICBs in experimental gliomas. Targeting glucocorticoid-induced TNFR-related receptor (GITR) in Treg cells using an agonistic antibody (alpha GITR) promotes CD4 Treg cell differentiation into CD4 effector T cells, alleviates Treg cell-mediated suppression of anti-tumor immune response, and induces potent anti-tumor effector cells in GBM. The reprogrammed GBM-infiltrating Treg cells express genes associated with a Th1 response signature, produce IFN gamma, and acquire cytotoxic activity against GBM tumor cells while losing their suppressive function. alpha GITR and alpha PD1 antibodies increase survival benefit in three experimental GBM models, with a fraction of cohorts exhibiting complete tumor eradication and immune memory upon tumor re-challenge. Moreover, alpha GITR and alpha PD1 synergize with the standard of care treatment for newly-diagnosed GBM, enhancing the cure rates in these GBM models. Glioblastomas (GBM) are frequently resistant to immune checkpoint blockade therapy. Here the authors show that treatment with an agonistic anti-GITR antibody converts tumor infiltrating regulatory T cells to effector cells, overcoming resistance to PD1 blockade in preclinical models of GBM.

Automated summary

In this study, researchers found that treatment with an agonistic anti-GITR antibody converts tumor infiltrating regulatory T cells to effector cells, overcoming resistance to PD1 blockade in preclinical models of GBM.