Study Overview: This study is for adults with Chronic Lymphocytic Leukemia (CLL), a type of blood cancer. It looks at how well two medicines, **venetoclax** and **obinutuzumab**, work together to treat CLL if the disease comes back after the first treatment. Participants will be divided into two groups based on when their CLL returned after the first treatment. Treatment Plan: Participants will receive oral venetoclax and intravenous (IV) obinutuzumab in 28-day cycles. The treatment includes 6 cycles with both drugs, and then 6 to 18 more cycles of venetoclax alone, lasting a total of 12 to 24 cycles. Key Points: - **Study Duration:** 12 to 24 treatment cycles, with regular hospital or clinic visits. - **Participation Requirements:** Must have completed a previous venetoclax treatment and experienced CLL return after 12-24 months. - **Considerations:** This study might be more demanding than standard care, with regular medical assessments and tests. Participants should discuss with their doctors about potential side effects, benefits, and if this study is suitable for them.