Immune Profiling of CLL/SLL Treated With First-Line Pirtobrutinib

Background: Chronic lymphocytic leukemia (CLL) and small lymphocytic lymphoma (SLL) are blood cancers that affect certain white blood cells. Advanced forms of these diseases are difficult to treat. Pirtobrutinib is a drug approved to treat CLL and SLL after 2 previous treatments. Researchers want to know how this drug affects the immune system in those who have not yet started other treatments for CLL or SLL. Objective: To test pirtobrutinib as a first-line treatment for CLL or SLL. Eligibility: People aged 18 years and older with untreated CLL or SLL. Design: Participants will be screened. They will have a physical exam with blood tests. They will have imaging scans and tests of their heart function. They will have a lymph node biopsy: A large needle will be inserted into a lymph node to collect a small piece of tissue. Pirtobrutinib is a tablet taken by mouth. Participants will take 2 to 4 tablets daily in 4-week cycles. Participants will have clinic visits once every 4 weeks for the first 3 months. Then they will be seen once every 3 months. Imaging scans, lymph node biopsy, and other tests will be repeated at various study visits. A bone marrow biopsy (collection of soft tissue from inside a bone) may be done if there is no evidence of disease after 1 year of treatment with the study drug. Participants may opt to have cancer and immune cells collected from their blood. The cells will be used for research. Participants will have a clinic visit 1 month after their last dose of the study drug. Then they will have follow-up visits or phone calls every 6 to 12 months....