Ibrutinib, an inhibitor of Bruton’s tyrosine kinase (BTK) and IL-2-inducible T-cell kinase (ITK) (Figure 4), was one of the first drugs ever to be used alongside CAR-T cells, based on observations that ibrutinib could extend the in vivo persistence of T cells and reduce the immunosuppressive profile of lymphoma cells [38,39]. Here, BTK is linked to lymphoma.