Ibrutinib-biotin (Compound 1-5) is a probe that consists of Ibrutinib linked to biotin via a long chain linker. Ibrutinib is a TEC family kinase inhibitor. The TEC kinase family is composed of five members, TEC, BTK (Bruton's Tyrosine Kinase), ITK (interleukin-2-inducible T-cell kinase)/EMT/TSK, BMX and TXK/RLK. The TEC family kinases participate in phosphotyrosine- mediated and phospholipid-mediated signaling systems. Many TEC family proteins are abundantly expressed in hematopoietic tissues, and play important roles in the growth and differentiation processes of blood cells[1].