• Esther Drent, Renée Poels, Ruud Ruiter, van de DonkNiels W C JNWCJDepartment of Haematology, Amsterdam University Medical Centers, Cancer Center Amsterdam, Location VUmc, Amsterdam, the Netherlands., Sonja Zweegman, Huipin Yuan, Joost de Bruijn, Michel Sadelain, Henk M Lokhorst, GroenRichard W JRWJDepartment of Haematology, Amsterdam University Medical Centers, Cancer Center Amsterdam, Location VUmc, Amsterdam, the Netherlands., Tuna Mutis, and Maria Themeli.
• Department of Haematology, Amsterdam University Medical Centers, Cancer Center Amsterdam, Location VUmc, Amsterdam, the Netherlands.
• Clin Cancer Res. 2019 Jul 1; 25 (13): 4014-4025.

PurposeTargeting nonspecific, tumor-associated antigens (TAA) with chimeric antigen receptors (CAR) requires specific attention to restrict possible detrimental on-target/off-tumor effects. A reduced affinity may direct CAR-engineered T (CAR-T) cells to tumor cells expressing high TAA levels while sparing low expressing normal tissues. However, decreasing the affinity of the CAR-target binding may compromise the overall antitumor effects. Here, we demonstrate the prime importance of the type of intracellular signaling on the function of low-affinity CAR-T cells.Experimental DesignWe used a series of single-chain variable fragments (scFv) with five different affinities targeting the same epitope of the multiple myeloma-associated CD38 antigen. The scFvs were incorporated in three different CAR costimulation designs and we evaluated the antitumor functionality and off-tumor toxicity of the generated CAR-T cells in vitro and in vivo.ResultsWe show that the inferior cytotoxicity and cytokine secretion mediated by CD38 CARs of very low-affinity (K d < 1.9 × 10-6 mol/L) bearing a 4-1BB intracellular domain can be significantly improved when a CD28 costimulatory domain is used. Additional 4-1BB signaling mediated by the coexpression of 4-1BBL provided the CD28-based CD38 CAR-T cells with superior proliferative capacity, preservation of a central memory phenotype, and significantly improved in vivo antitumor function, while preserving their ability to discriminate target antigen density.ConclusionsA combinatorial costimulatory design allows the use of very low-affinity binding domains (K d < 1 μmol/L) for the construction of safe but also optimally effective CAR-T cells. Thus, very-low-affinity scFvs empowered by selected costimulatory elements can enhance the clinical potential of TAA-targeting CARs.©2019 American Association for Cancer Research.

45 keywords...

hide…