Ibrutinib is primarily used in the treatment of certain types of cancers, particularly those affecting the blood and lymph nodes. It is highly effective in managing chronic lymphocytic leukemia (CLL), small lymphocytic lymphoma (SLL), and mantle cell lymphoma (MCL). The drug works by inhibiting Bruton's tyrosine kinase (BTK), an enzyme crucial for the survival and proliferation of malignant B-cells. This targeted approach helps to slow down or stop the progression of these cancers. Additionally, ibrutinib is used in treating Waldenström's macroglobulinemia, a rare type of non-Hodgkin lymphoma. Its ability to selectively target cancer cells while sparing healthy cells makes it a valuable option in oncology, offering improved outcomes and reduced side effects compared to traditional chemotherapy.