Inclusion Criteria:

          -  Age >/= 60 years

          -  Histological confirmation of relapsed or refractory AML after prior anti-leukemic
             therapy by WHO Classification

          -  Not eligible for cytotoxic therapies

          -  Ineligible for allogeneic stem cell transplant

          -  Life expectancy of at least 12 weeks

          -  Eastern Cooperative Oncology Group (ECOG) Performance Status 0-2

          -  Adequate liver and renal function

        Exclusion Criteria:

          -  Patients with acute promyelocytic leukemia (French-American-British [FAB] class M3
             AML)

          -  Known active central nervous system (CNS) involvement with AML at study entry

          -  Prior exposure to Bcl-2 inhibitors, murine double minute 2 (MDM2) antagonists or
             prior exposure to experimental treatment targeting Raf, mitogen-activated protein
             kinase (MEK), or the mitogen-activated protein kinase (MAPK) RAS/RAF/MEK/ERK MAPK
             pathway

          -  Positive for hepatitis C virus (HCV), hepatitis B surface antigen (HBsAg) and known
             history of HIV, malignancy, active infection and cardiovascular diseases (CVs)

          -  Received strong cytochrome (CYP) 3A inhibitors, moderate CYP3A inhibitors, strong
             CYP3A inducers and moderate CYP3A inducers within 7 days prior to initiation of study
             treatment

          -  History of symptomatic Clostridium difficile infection within 1 month prior to dosing

        Additional phase specific exclusion criteria:

        Phase Ib Dose Escalation Arm A (Venetoclax and Cobimetinib)

          -  History or evidence of retinal pathology on ophthalmologic examination that is
             considered a risk factor for neurosensory retinal detachment/central serous
             chorioretinopathy (CSCR), retinal vein occlusion (RVO), or neovascular macular
             degeneration

          -  Left ventricular ejection fraction (LVEF) below institutional lower limit of normal
             (LLN) or below 50%, whichever is lower

        Phase Ib Dose-Escalation Arm B (Venetoclax and Idasanutlin):

        Received the following within 7 days prior to the initiation of study treatment:

          -  Strong CYP2C8 inhibitors or CYP2C8 substrates

          -  OATP1B1/3 substrates

        Received the following within 14 days prior to the initiation of study treatment:

        * Strong CYP2C8 inducers

          -  Received hormonal therapy (apart from luteinizing hormone releasing hormone
             agonist/antagonist for prostate cancer and hormone replacement therapy) within 2
             weeks prior to the first dose of study treatment

          -  History of liver cirrhosis by radiologic, clinical or laboratory data, or biopsy
             despite normal liver function tests

        Phase II Expansion Arm A and Arm B:

          -  Received the following within 7 days prior to the initiation of study treatment:

               -  Strong CYP2C8 inhibitors or CYP2C8 substrates

               -  OATP1B1/3 substrates

          -  Received the following within 14 days prior to the initiation of study treatment:

             * Strong CYP2C8 inducers

          -  History or evidence of retinal pathology on ophthalmologic examination that is
             considered a risk factor for neurosensory retinal detachment/CSCR, RVO, or
             neovascular macular degeneration

          -  LVEF below institutional LLN or below 50%, whichever is lower

          -  Received hormonal therapy (apart from luteinizing hormone releasing hormone
             agonist/antagonist for prostate cancer and hormone replacement therapy) within 2
             weeks prior to the first dose of study treatment

          -  History of liver cirrhosis by radiologic, clinical or laboratory data, or biopsy
             despite normal liver function tests