The goal of this study is to test mosunetuzumab given alone or in combination with a Bruton tyrosine kinase inhibitor (BTKi, such as ibrutinib, acalabrutinib, zanubrutinib, or pirtobrutinib) in participants with CLL (chronic lymphocytic leukemia) or small lymphocytic lymphoma (SLL).
The names of the study drugs in this research study are:
* Mosunetuzumab
* BTK inhibitor: Ibrutinib, acalabrutinib, zanubrutinib, or pirtobrutinib