BTK and B-cell chronic lymphocytic leukemia: Effective available treatment options for patients with chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) who relapse after becoming refractory to both a covalent Bruton Tyrosine Kinase inhibitor (cBTKi) and a B cell leukemia/lymphoma 2 inhibitor (BCL2i) remain limited, and prognosis is very poor.