The Intracellular Domain of CD40 is a Potent Costimulatory Element in Chimeric Antigen Receptors.

The costimulatory domains incorporated into second-generation and third-generation chimeric antigen receptors (CARs) strongly influence CAR-T-cell function. Here, we explored second-generation and third-generation CARs harboring the signaling domain of the CD40 receptor as a new costimulatory element in comparison with similar CARs carrying the 4-1BB domain. In CARs of both generations, CD40 was more potent than 4-1BB in triggering the NF-κB signaling pathway. In human T cells from 2 donors, CD40 was comparable to 4-1BB in upregulating costimulatory and activation markers, inducing proinflammatory cytokine secretion and mediating target cell killing. Interestingly, differences in the response pattern of T cells from the 2 donors with respect to CD40 and 4-1BB were evident. We conclude that in human T cells, the CD40 signaling domain is a potent costimulatory element in both second-generation and third-generation CARs.