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

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.

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.

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.

These results provide a strong rationale for evaluating the iCas9.B7-H3 CAR T cell strategy in clinical trials for patients with advanced ICC.