Chimeric antigen receptors (CARs) are artificial fusion proteins that incorporate antigen-recognition domains and T cell signaling domains. CD30 is a cell surface protein expressed on Hodgkin's lymphoma, some T cell lymphomas, and some B cell lymphomas. CD30 has a restricted expression pattern in normal cells, so CD30 has good potential as a clinical target for CAR T cells. We compared three different anti-CD30 CAR designs incorporating a single-chain variable fragment derived from the 5F11 fully human monoclonal antibody. 5F11-28Z has hinge, transmembrane, and costimulatory domains from CD28 and a CD3ζ T cell activation domain. 5F11-CD828Z has hinge and transmembrane domains from CD8α, a CD28 costimulatory domain, and a CD3ζ T cell activation domain. 5F11-CD8BBZ is identical to 5F11-CD828Z, except for the replacement of the CD28 moiety with a 4-1BB moiety. We found that T cells expressing 5F11-CD8BBZ had lower levels of CD30-specific degranulation and cytokine release compared with CD28-containing CARs. When compared to the CD28-containing CARs, T cells expressing 5F11-CD8BBZ had higher levels of nonspecific functional activity, including degranulation, cytokine release, and proliferation, when stimulated with CD30-negative target cells. We established tumors in nod-scid common gamma-chain deficient (NSG) mice and treated the tumors with T cells expressing different CARs. T cells expressing 5F11-28Z were most effective at eradicating tumors. T cells expressing 5F11-CD828Z had intermediate effectiveness, and T cells expressing 5F11-CD8BBZ were least effective. CD30+ T cells are lost from cultures of T cells containing 5F11-28Z-expressing T cells. This indicated the killing of CD30+ T cells by the 5F11-28Z-expressing T cells. Despite this, the number of T cells in the cultures consistently accumulated to numbers needed for use in a clinical trial. Based on all in vitro and murine experiments comparing the different CARs, we selected 5F11-28Z for further development, and we have initiated a clinical trial testing 5F11-28Z T cells.
Keywords: 4-1BB; CAR; CD28; CD30; chimeric antigen receptor.