Spebrutinib also less potently inhibits Yes, c-Src, Brk, Lyn, and Fyn with IC50s of 723 nM, 1.729 μM, 2.43 μM, 4.4 μM, and 7.15 μM, rspectively. Spebrutinib (CC-292) is a covalent, highly selective, orally active inhibitor of Btk with IC50 value of 0.5 nM. The concentration at which Spebrutinib inhibits 90% of Btk activity in Ramos cells is 35 nM while the concentration of Spebrutinib required for 90% occupancy of Btk is 39 nM[1]. Extensive analysis has revealed that the EC50 of Btk occupancy from a Spebrutinib dose-response in Ramos cells (EC50=6 nM) correlated directly with the cellular EC50 of Btk kinase inhibition with Spebrutinib (EC50=8 nM).