Background Glypican-3 (GPC-3) is an oncofetal protein that is highly expressed in various solid tumors including hepatocellular carcinoma (HCC) but is rarely expressed in healthy adult tissues and serves as a therapeutic target of interest. Autologous αβ chimeric antigen receptor (CAR) T cell therapy has established clinical benefit in hematologic malignancies but limited success in solid tumors due to numerous challenges including poor T cell homing, heterogenous antigen expression, and hostile tumor microenvironments.1 These challenges may be overcome by the Vδ1 subset of gamma delta T cells due to their natural peripheral tissue tropism and ability to recognize and kill tumor cells through MHC-independent antigens upregulated under stress.2 Allogeneic Vδ1 T cells engineered with CARs can have enhanced intrinsic antitumor activity and overcome challenges of allogeneic αβ T cells, including graft-versus-host disease (GvHD). Here, we describe the first preclinical evaluation of ADI-002, a next-generation allogeneic CAR Vδ1 T cell therapy targeting GPC-3 and armored with IL-15, for the treatment of solid tumors.
Methods Vδ1 T cells were expanded from healthy donor PBMCs and transduced to express a 4–1BB/CD3z CAR against GPC-3 that encodes constitutively-secreted IL-15 (sIL-15), which we hypothesized could sustain proliferation and antitumor activity of intratumoral GPC-3.CAR Vδ1 T cells. In vitro characterization included co-culture with HCC targets expressing high (HepG2) and low (PLC/PRF/5) GPC-3, phenotypic analysis by flow cytometry, and cytokine production by multiplexed immunoassay. For in vivo assessment, immunodeficient NSG mice were subcutaneously injected with HepG2 tumor cells and treated with a single dose of GPC-3.CAR Vδ1 T cells. Tissues were harvested 7 days post transfer and analyzed for Vδ1 T cell tissue homing and proliferation, or at study end and analyzed for GvHD by immunohistochemistry.
Results GPC-3.sIL-15.CAR Vδ1 T cells expanded over 10,000-fold and routinely reached >80% purity. Expanded Vδ1 T cells showed a primarily naïve-like phenotype (CD45RA+CD27+) with minimal exhaustion receptor expression and displayed robust proliferation, cytokine production, and cytotoxic activity against HCC cell lines in vitro. In vivo, GPC-3.sIL-15.CAR Vδ1 T cells primarily accumulated and proliferated in tumors, and a single dose could efficiently control tumor burden without causing GvHD. When compared to GPC-3.CAR Vδ1 T cells lacking sIL-15, GPC-3.sIL-15.CAR Vδ1 T cells displayed greater tumor-specific proliferation that resulted in enhanced tumor control (figure 1).
Conclusions Expanded Vδ1 T cells engineered with GPC-3.CAR and sIL-15 represent a promising approach for safe and effective off-the-shelf treatment of HCC and support further investigation in the clinical setting.
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Ethics Approval All mouse experiments were performed in accordance with the Guide for the Care and Use of Laboratory Animals and followed all institutional and national guidelines and after appropriate approvals.