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Updated: Dec 31, 2025
Generation of CAR T Cells for Adoptive Therapy in the Context of Glioblastoma Standard of Care
Published on: February 16, 2015
EGFR806-CAR T cells selectively target a tumor-restricted EGFR epitope in glioblastoma
Ali C Ravanpay1,2, Juliane Gust3,4, Adam J Johnson1
1Ben Towne Center for Childhood Cancer Research, Seattle Children's Research Institute, Seattle, WA, U.S.A.
Abstract:
Targeting solid tumor antigens with chimeric antigen receptor (CAR) T cell therapy requires tumor specificity and tolerance toward variability in antigen expression levels. Given the relative paucity of unique cell surface proteins on tumor cells for CAR targeting, we have focused on identifying tumor-specific epitopes that arise as a consequence of target protein posttranslational modification. We designed a CAR using a mAb806-based binder, which recognizes tumor-specific untethered EGFR. The mAb806 epitope is also exposed in the EGFRvIII variant transcript. By varying spacer domain elements of the CAR, we structurally tuned the CAR to recognize low densities of EGFR representative of non-gene amplified expression levels in solid tumors. The appropriately tuned short-spacer 2nd generation EGFR806-CAR T cells showed efficient in vitro cytokine secretion and glioma cell lysis, which was competitively blocked by a short peptide encompassing the mAb806 binding site. Unlike the nonselective Erbitux-based CAR, EGFR806-CAR T cells did not target primary human fetal brain astrocytes expressing wild-type EGFR, but showed a similar level of activity compared to Erbitux-CAR when the tumor-specific EGFRvIII transcript variant was overexpressed in astrocytes. EGFR806-CAR T cells successfully treated orthotopic U87 glioma implants in NSG mice, with 50% of animals surviving to 90 days. With additional IL-2 support, all tumors were eradicate without recurrence after 90 days. In a novel human induced pluripotent stem cell (iPSC)-derived teratoma xenograft model, EGFR806-CAR T cells infiltrated but were not activated in EGFR+ epidermal cell nests as assessed by Granzyme B expression. These results indicate that EGFR806-CAR T cells effectively and selectively target EGFR-expressing tumor cells.
Insights
Chimeric antigen receptor (CAR) T cell therapy targeting solid tumors can be improved by focusing on tumor-specific epitopes. A novel EGFR806-CAR T cell therapy demonstrated effective and selective targeting of EGFR-expressing tumor cells in preclinical models.
Area of Science:
- Oncology
- Immunotherapy
- Molecular Biology
Background:
- Chimeric antigen receptor (CAR) T cell therapy faces challenges in targeting solid tumors due to antigen variability and the need for tumor specificity.
- Identifying unique tumor-specific epitopes, particularly those arising from posttranslational modifications, is crucial for effective CAR T cell development.
- Epidermal growth factor receptor (EGFR) is a target, but its expression variability and presence on normal tissues complicate selective targeting.
Purpose of the Study:
- To design and evaluate a novel CAR T cell therapy targeting a tumor-specific EGFR epitope for enhanced solid tumor treatment.
- To structurally tune the CAR to recognize low EGFR expression levels and ensure tumor selectivity.
- To assess the efficacy and safety of the engineered CAR T cells in preclinical solid tumor models.
Main Methods:
- Designed a CAR T cell therapy (EGFR806-CAR) using a binder (mAb806) recognizing tumor-specific untethered EGFR, including the EGFRvIII variant.
- Structurally tuned the CAR by varying spacer domains to optimize recognition of low EGFR densities.
- Evaluated in vitro activity (cytokine secretion, cell lysis) and in vivo efficacy in glioma and teratoma xenograft models, comparing with a standard EGFR-targeting CAR.
Main Results:
- EGFR806-CAR T cells demonstrated efficient in vitro glioma cell lysis and cytokine secretion, selectively targeting tumor cells over normal astrocytes expressing wild-type EGFR.
- In vivo studies showed successful treatment of orthotopic U87 glioma implants, with significant survival benefit and complete tumor eradication with IL-2 support.
- In a human iPSC-derived teratoma model, EGFR806-CAR T cells infiltrated tumors but remained quiescent in normal EGFR-expressing tissues, indicating safety.
Conclusions:
- The engineered EGFR806-CAR T cells exhibit potent and selective activity against EGFR-expressing solid tumors.
- This approach overcomes limitations of targeting variable antigen expression and off-tumor toxicity.
- EGFR806-CAR T cells represent a promising strategy for solid tumor immunotherapy.
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