B7-H3 CAR T cells eradicate intrahepatic cholangiocarcinoma and induce durable response

BACKGROUND: Intrahepatic cholangiocarcinoma (ICC) is the second most common primary liver tumor, with an increasing incidence over the past two decades. While surgery offers a curative option, most patients present with advanced disease, for which current therapeutic options are ineffective. B7-H3 is an immune checkpoint molecule that is overexpressed in ICC relative to normal tissue, making it an attractive therapeutic target. Utilizing in vitro and in vivo models, we investigated the efficacy of a B7-H3-targeted CAR T to treat ICC. METHODS: B7-H3 CAR T cells were generated from peripheral blood mononuclear cells of normal donors, transduced with a retroviral vector encoding a second generation B7-H3 specific CAR construct, incorporating an inducible caspase9 (iCas9) suicide gene-based safety switch. The anti-tumor activity of iCas9.B7-H3 CAR T cells against ICC was tested in vitro using human ICC cell lines and patient-derived organotypic tumor spheroids (PDOTS) and in vivo using xenograft models of ICC. RESULTS: Human ICC cell lines, resected ICC samples from patients, and ICC tissue microarrays demonstrate homogeneous expression of B7-H3. iCas9.B7-H3 CAR T cells demonstrated potent anti-tumor activity in vitro against multiple patient-derived ICC cell lines. A single systemic dose of iCas9.B7-H3 CAR T cells induced complete and sustained eradication of orthotopic ICC tumors in a preclinical mouse model, even after tumor re-challenge. Locoregional delivery of CAR T cells via splenic and intra-tumoral injection was equally effective as systemic therapy. CONCLUSIONS: These results provide a strong rationale for evaluating the iCas9.B7-H3 CAR T cell strategy in clinical trials for patients with advanced ICC.