Targeting TGFβ docking receptor Glycoprotein A Repetitions Predominant (GARP) via novel chimeric antigen receptor (CAR)-T cell platform to treat glioblastoma.

Background: Glycoprotein A-repetitions predominant (GARP) is a cell surface non-signaling receptor for docking and activating latent transforming growth factor beta (LTGFβ) expressed by regulatory T cells, platelets and tumor cells. In lung and breast cancers, its expression correlates with advanced stage and poor prognosis - suggesting that GARP could act as a therapeutic target. This study examines the therapeutic impact of targeting GARP in glioblastoma (GBM) via a novel anti-GARP chimeric antigen receptor-expressing T cell (CAR-T) modality in murine models of GBM.

Methods: We examined multiple human glioma databases to correlate the expression of GARP with clinical outcomes. We then performed multi-plex imaging of human GBM samples to understand the impact of GARP expression on the tumor microenvironment (TME). Importantly, we developed a novel anti-GARP CAR-T cell strategy to treat GBM. We examine if this therapy is efficacious against orthotopic models of GBM, in both immunocompetent syngeneic and immunodeficient mice.

Results: We demonstrate that elevated GARP expression in human GBM correlates with poor overall survival, mesenchymal subtype, and gene signatures associated with angiogenesis and immune exclusion in the TME. Our novel anti-GARP CAR-T is efficacious in vitro and in vivo, against multiple preclinical models of GBM including patient-derived xenograft (PDX) models without significant toxicity.

Conclusions: GARP-LTGFβ plays a key role in the development and prognostics of GBM and GARP-targeted CAR-T therapy shows promising efficacy and safety in murine orthotopic GBM models. A first-in-human phase I clinical trial for patients with recurrent GBM began to enroll patients in May 2025 (NCT06964737).