This study aims to test the safety and effectiveness of a drug called Pirtobrutinib in adults with chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma (SLL). **Leukemia** is a type of blood cancer, while **lymphoma** affects the immune system. To join, you must have CLL or SLL, have tried 1-3 different treatments before, and taken a specific type of medicine called a Bruton tyrosine kinase (BTK) inhibitor. A BTK inhibitor helps stop cancer cell growth. The study will last around 3 years. You should not join if you've already tried a different kind of BTK medicine that breaks down cancer cells or if you have other serious health issues like a known brain involvement or recent other cancers.

• The study lasts about 3 years.
• You must be able to swallow pills.
• Not suitable if you've had severe bleeding from BTK treatments.