Novel TCR-like CAR-T cells targeting an HLA∗0201-restricted SSX2 epitope display strong activity against acute myeloid leukemia

Scott Raskin; Stacey Van Pelt; Keri Toner; Preethi Bala Balakrishnan; Hema Dave; Catherine M Bollard; Eric Yvon

doi:10.1016/j.omtm.2021.09.008

Novel TCR-like CAR-T cells targeting an HLA∗0201-restricted SSX2 epitope display strong activity against acute myeloid leukemia

Mol Ther Methods Clin Dev. 2021 Oct 1:23:296-306. doi: 10.1016/j.omtm.2021.09.008. eCollection 2021 Dec 10.

Authors

Scott Raskin¹, Stacey Van Pelt^{2

3}, Keri Toner^{1

3}, Preethi Bala Balakrishnan², Hema Dave^{2

3}, Catherine M Bollard^{1

2

3}, Eric Yvon^{3

4}

Affiliations

¹ Program for Cell Enhancement and Technologies for Immunotherapy, Children's National Health System, Washington, DC 20010, USA.
² Institute for Biomedical Sciences, The George Washington University, Washington, DC 20052, USA.
³ The George Washington University Cancer Center, Washington, DC 20052, USA.
⁴ Department of Medicine, The George Washington University, Washington, DC 20052, USA.

Abstract

The synovial sarcoma X breakpoint 2 (SSX2) belongs to a multigene family of cancer-testis antigens and can be found overexpressed in multiple malignancies. Its restricted expression in immune-privileged normal tissues suggest that SSX2 may be a relevant target antigen for chimeric antigen receptor (CAR) therapy. We have developed a T cell receptor (TCR)-like antibody (Fab/3) that binds SSX2 peptide 41-49 (KASEKIFYV) in the context of HLA-A∗-0201. The sequence of Fab/3 was utilized to engineer a CAR with the CD3 zeta intra-cellular domain along with either a CD28 or 4-1BB costimulatory endodomain. Human T cells from HLA-A2⁺ donors were transduced to mediate anti-tumor activity against acute myeloid leukemia (AML) tumor cells. Upon challenge with HLA-A2⁺/SSX2⁺ AML tumor cells, CAR-expressing T cells released interferon-γ and eliminated the tumor cells in a long-term co-culture assay. Using the HLA-A2⁺ T2 cell line, we demonstrated a strong specificity of the single-chain variable fragment (scFv) for SSX2 p41-49 and the closely related SSX3 p41-49, with no response against the others SSX-homologous peptides or unrelated homologous peptides. Since SSX3 has not been observed in tumor cells and expression cannot be induced by pharmacological intervention, SSX2_41-49 represents an attractive target for CAR-based cellular therapy to treat multiple types of cancer.

Keywords: AML; CAR; CTA; SSX; T cell receptor-like antibody; TCR-like antibody; acute myeloid leukemia; cancer-testis antigen; cellular therapy; chimeric antigen receptor; synovial sarcoma X breakpoint.