RN-486 (Table 3) [49,50] is under preclinical investigation, in particular for RA; it presents IC50 values of 4nM compared to BTK, as well as some activity compared to Slk and Tec (with IC50 values of 43 nM and 64 nM, respectively) [4,51,52]. Here, BTK is linked to rheumatoid arthritis.