A Study to Compare the Efficacy and Safety of Obinutuzumab + Venetoclax (GDC-0199) Versus Obinutuzumab + Chlorambucil in Participants With Chronic Lymphocytic Leukemia

Inclusion Criteria:

- Documented previously untreated CLL according to the International Workshop on Chronic
Lymphocytic Leukemia (IWCLL) criteria

- CLL requiring treatment according to IWCLL criteria

- Total Cumulative Illness Rating Scale (CIRS score) greater than (>) 6

- Adequate marrow function independent of growth factor or transfusion support within 2
weeks of screening as per protocol, unless cytopenia is due to marrow involvement of
CLL

- Adequate liver function

- Life expectancy > 6 months

- Agreement to use highly effective contraceptive methods per protocol

Exclusion Criteria:

- Transformation of CLL to aggressive Non-Hodgkin's lymphoma (Richter's transformation
or pro-lymphocytic leukemia)

- Known central nervous system involvement

- Participants with a history of confirmed progressive multifocal leukoencephalopathy
(PML)

- An individual organ/ system impairment score of 4 as assessed by the CIRS definition
limiting the ability to receive the treatment regimen of this trial with the exception
of eyes, ears, nose, throat organ system

- Participants with uncontrolled autoimmune hemolytic anemia or immune thrombocytopenia

- Inadequate renal function

- History of prior malignancy, except for conditions as listed in the protocol if
patients have recovered from the acute side effects incurred as a result of previous
therapy

- Use of investigational agents or concurrent anti-cancer treatment within the last 4
weeks of registration

- Participants with active bacterial, viral, or fungal infection requiring systemic
treatment within the last two months prior to registration

- History of severe allergic or anaphylactic reactions to humanized or murine monoclonal
antibodies or known sensitivity or allergy to murine products

- Hypersensitivity to chlorambucil, obinutuzumab, or venetoclax or to any of the
excipients

- Pregnant women and nursing mothers

- Positive test results for chronic hepatitis B virus (HBV) infection (defined as
positive hepatitis B surface antigen [HBsAg] serology) or positive test result for
hepatitis C (hepatitis C virus [HCV] antibody serology testing)

- Participants with known infection with human immunodeficiency virus (HIV) or human
T-cell leukemia virus-1 (HTLV-1)

- Requires the use of warfarin, marcumar, or phenprocoumon

- Received agents known to be strong and moderate Cytochrome P450 3A inhibitors or
inducers within 7 days prior to the first dose of study drug