A Study of Obinutuzumab in Combination With Idasanutlin and Venetoclax in Participants With Relapsed or Refractory (R/R) Follicular Lymphoma (FL) or Rituximab in Combination With Idasanutlin and Venetoclax in Participants With R/R Diffuse Large B-Cell Lymphoma (DLBCL)

Inclusion Criteria:

- Eastern Cooperative Oncology Group (ECOG) performance status of 0, 1, or 2

- B-cell lymphoma classified as either of the following: R/R FL after treatment with at
least one prior chemoimmunotherapy regimen that included an anti-cluster of
differentiation 20 (CD20) monoclonal antibody; R/R DLBCL after treatment with at least
one prior chemoimmunotherapy regimen that included an anti-CD20 monoclonal antibody in
participants who are not eligible for second line combination chemotherapy and
autologous stem-cell transplantation, have failed second line combination
chemotherapy, or experienced disease progression following autologous stem-cell
transplantation

- Histologically documented CD20-positive lymphoma

- Fluorodeoxyglucose (FDG)-avid lymphoma (that is [i.e.], PET-positive lymphoma)

- At least one bi-dimensionally measurable lesion (greater than [>] 1.5 centimeters [cm]
in its largest dimension by CT scan or magnetic resonance imaging [MRI])

- Availability of a representative tumor specimen and the corresponding pathology report
for retrospective central confirmation of the diagnosis of FL or DLBCL

Exclusion Criteria:

- Known CD20-negative status at relapse or progression

- Prior allogeneic stem-cell transplantation (SCT)

- Completion of autologous SCT within 100 days prior to Day 1 of Cycle 1

- Prior standard or investigational anti-cancer therapy as specified:
Radioimmunoconjugate within 12 weeks prior to Day 1 of Cycle 1; Monoclonal antibody or
antibody-drug conjugate within 4 weeks prior to Day 1 of Cycle 1; Radiotherapy,
chemotherapy, hormonal therapy, or targeted small-molecule therapy within 2 weeks
prior to Day 1 of Cycle 1

- Clinically significant toxicity (other than alopecia) from prior therapy that has not
resolved to Grade less than or equal to ( Institute Common Terminology Criteria for Adverse Events [NCI CTCAE] version 4.0)
prior to Day 1 of Cycle 1

- Grade 3b FL

- History of transformation of indolent disease to DLBCL (expansion-phase only)

- Central nervous system lymphoma or leptomeningeal infiltration

- Treatment with systemic corticosteroids >20 mg/day, prednisone or equivalent

- Clinical conditions requiring treatment with oral or parenteral anticoagulants or
antiplatelet agents unless treatment can be discontinued 7 days (or 5 half-lives)
prior to initiation of study treatment (except used as flushes for indwelling
catheters)

- History of severe allergic or anaphylactic reaction to humanized or murine monoclonal
antibodies

- Known hypersensitivity or allergy to murine products or any component of the
obinutuzumab, rituximab, idasanutlin, or venetoclax formulation

- Current or history of hepatitis B virus (HBV) or hepatitis C virus (HCV) infection:
positive for hepatitis B surface antigen (HBsAg), total hepatitis B core antibody
(HBcAb), or HCV antibody at screening

- History of progressive multifocal leukoencephalopathy (PML)

- History of other malignancy that could affect compliance with the protocol or
interpretation of results

- Evidence of any significant, uncontrolled concomitant disease that could affect
compliance with the protocol or interpretation of results

- Non-malignant medical illnesses that are uncontrolled or whose control may be
jeopardized by study treatment, such as severe hereditary coagulation disorders or
insulin-dependent diabetes mellitus that is not optimally controlled with medical
management (example, presence of ketoacidosis)

- Major surgical procedure other than for diagnosis within 28 days prior to Day 1 of
Cycle 1, or anticipation of a major surgical procedure during the study

- Inadequate hematologic function (unless due to underlying lymphoma), defined as
follows: Hemoglobin less than (<) 9 grams per decilitre (g/dL), absolute neutrophil
count (ANC) <1.5*10^9 cells per liter (cells/L), platelet count <75*10^9 cells/L

- Any of the following abnormal laboratory values (unless due to underlying lymphoma):
International normalized ratio (INR) or prothrombin time (PT) >1.5*upper limit of
normal (ULN) in the absence of therapeutic anticoagulation; partial thromboplastin
time (PTT) or activated partial thromboplastin time (aPTT) >1.5*ULN in the absence of
a lupus anticoagulant

- Life expectancy <3 months