ANTI-TUMOR ACTIVITY OF ENDOGLIN CAR T CELLS AGAINST ADVANCED SARCOMAS

• Published in: Cytotherapy (Oxford, England) Vol. 26; no. 6; p. S174
• Main Authors: Joseph, S.K., Berger, H.R., Maharana, M., Kurenbekova, L., Delaidelli, A., Malik, S., Dasgupta, A., Ozcan, A.I., Morris, J., Gad, A.Z., Seon, B.K., McKenna, M., Sorensen, P.M., Hegde, M., Yustein, J.T., Ahmed, N.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01-06-2024
• Subjects: Endoglin CAR T cells; Immunotherapy; Sarcomas; Sarcomas; Immunotherapy; Endoglin CAR T cells
• ISSN: 1465-3249; 1477-2566
• DOI: 10.1016/j.jcyt.2024.03.343

The prognosis for metastatic sarcoma in children remains bleak. Cellular immunotherapy with chimeric antigen receptor T cells (CAR-T) can be a suitable approach for these hard-to-treat cancers. However, a paucity of relevant tumor-associated antigens exists in sarcoma, limiting their therapeutic potential. We describe the creation of a novel CAR-T against the surface protein endoglin (ENG, CD105), a TGF-β co-receptor, expresed on sarcomas. We identified ENG as a significant target of endogenous immune reactivity in an exceptional responder with metastatic sarcoma, after co-administration of HER2 CAR-T and lymphodepletion chemotherapy in our clinical study NCT00902044. We aim to target the broad expression of ENG on cancer cells, neovascular endothelial cells and cancer-associated fibroblasts in sarcomas using endoglin-directed CAR-T (ENG CAR-T).
To target ENG, we engineered iterations of second-generation CAR molecules combining the anti-ENG mAb c-SN6j, the intracellular signaling domain (ICD) derived from the CD28-, 41BB- or OX40-molecules and the CD3-ζ activating domain. Retroviral transduction was used to express the ENG CAR molecules on primary human T cells. The functional assessments for the ENG CAR-T included cytokine release, T-cell proliferation, impedance-based cytotoxicity, 3D spheroid disruption and anti-tumor efficacy in murine orthotopic xenograft models of sarcoma.
Co-culture of ENG CAR-T with sarcoma cell lines revealed the best outcomes with CD28-ICD-mediated signaling, displaying enhanced release of IFN-γ and IL-2, increased proliferation and robust cytotoxic responses in vitro. ENG CAR-T efficiently disrupted the formation of 3D spheroids in sarcoma lines, both independently and when co-cultured with fibroblast lines. In intratibial orthotopic models of osteosarcoma and Ewing sarcoma, as well as an intramuscular model of rhabdomyosarcoma, ENG-CART exhibited potent anti-tumor activity, extending survival rates in mice and delaying metastasis. In conclusion, the results suggest that the novel ENG CAR-T demonstrates anti-tumor activity in experimental models of advanced sarcomas