This clinical trial is focused on studying the effects of a treatment for Chronic Lymphocytic Leukemia (CLL), a type of cancer that affects the blood and bone marrow. The treatment being tested involves a combination of two medications: Venetoclax and Obinutuzumab. Venetoclax, also known by its code name ABT-199, is a small molecule that targets a specific protein in cancer cells, while Obinutuzumab is a type of medication called an antibody, which helps the immune system to attack cancer cells.

The purpose of this study is to evaluate how effective and safe this combination treatment is for patients whose CLL has returned after previous treatment. Participants in the study will receive Venetoclax in the form of a film-coated tablet taken orally, and Obinutuzumab as a solution for infusion, which means it is given directly into a vein. The study will follow participants over a period of time to monitor changes in their disease and any side effects they may experience.

Throughout the study, participants will be assessed to see how their disease responds to the treatment. The study aims to understand the overall response rate, which is the proportion of participants who show improvement in their condition. Other aspects being evaluated include how long it takes for the treatment to start working, how long the response lasts, and the time until any further treatment is needed. The study will also look at progression-free survival, which is the length of time during and after treatment that a patient lives with the disease without it getting worse, and overall survival, which is the length of time a patient lives after starting the treatment.