Chronic lymphocytic leukemia (CLL) is the most common adult leukemia. Although newer treatments have helped many patients, some people experience relapsed disease, meaning the cancer returns after treatment, or refractory disease, meaning the cancer does not respond to treatment. Small lymphocytic lymphoma (SLL) is a similar disease to CLL, but appears mainly in the lymph nodes rather than the blood. BGB-16673 is an investigational drug, meaning it is not approved by the United States Food and Drug Administration (FDA). It is described as selective, meaning it is designed to act mainly on one...