This study is for adults with specific types of blood cancer called **Chronic Lymphocytic Leukemia (CLL)** and **Small Lymphocytic Lymphoma (SLL)**. The study aims to evaluate the safety and effectiveness of a treatment named **JCAR017**. There are different parts to this study: Phase 1 will find the best dose of JCAR017, and Phase 2 will see how well it works. Some parts of the study will also test JCAR017 with other medicines like **ibrutinib** and **venetoclax**. Participants must have already tried other treatments without success. **Key Points**: - **Study Duration & Visits**: This study is divided into phases, requiring multiple visits to the study center. - **Compensation**: Participants may receive compensation for their time and travel. - **Risks & Benefits**: Potential risks include side effects from the treatment, but it may help manage cancer symptoms. To join, you must meet certain health criteria, such as having a specific diagnosis and previous treatment history. You also shouldn’t have certain health conditions or ongoing infections. Always discuss potential risks and benefits with your doctor before participating.