Elsubrutinib(ABBV-105) is a covalent, irreversible, potent, and highly selective inhibitor of Bruton’s Tyrosine Kinase (BTK), with an IC50 of 0.18 μM for BTK catalytic domain. It specifically inhibits BTK dependent cellular functions, including both BCR and FcγR mediated signaling. It also exhibits significant efficacy in pre-clinical mechanistic models of antibody production, as well as in models of rheumatoid arthritis and lupus.