Schéma : This is a multicenter, double-blind, randomized, placebo-controlled study designed to compare overall survival in participants with relapsed or refractory AML treated with idasanutlin in combination with cytarabine versus participants treated with placebo and cytarabine. Participants will receive induction treatment with idasanutlin/placebo and cytarabine (Cycle 1). Responding participants may continue to receive a maximum of further two cycles of consolidation (Cycle 2 and Cycle 3). Complete remission (CR), CR with incomplete platelet count recovery (CRp), overall remission rate (ORR), event-free survival (EFS), leukemia-free survival (LFS) and percentage of participants with an allogeneic hematopoietic stem cell transplant (HSCT) will also be compared between treatment arms. This study will include participants with and without TP53 wild type (TP53 WT) mutations.

Study Arms:
- Experimental: Idasanutlin plus Cytarabine
Participants will receive induction therapy idasanutlin and cytarabine for 5 days followed by 23 days of rest in Cycle 1 (treatment cycle length=28 days). Responding participants may continue with consolidation therapy for a maximum of 2 additional cycles including idasanutlin and cytarabine for 5 days followed by 23 days of rest in each cycle (treatment cycle length=28 days). After each cycle, for participants achieving CRp or complete remission with incomplete blood count recovery (CRi), up to 28 additional days are allowed for blood count recovery, if needed.
Interventions:
Drug: Cytarabine
Drug: Idasanutlin
- Placebo Comparator: Placebo plus Cytarabine
Participants will receive induction therapy idasanutlin matching placebo and cytarabine for 5 days followed by 23 days of rest in Cycle 1 (treatment cycle length=28 days). Responding participants may continue with consolidation therapy for a maximum of 2 additional cycles including idasanutlin matching placebo and cytarabine for 5 days followed by 23 days of rest in each cycle (treatment cycle length=28 days). After each cycle, for participants achieving CRp or CRi, up to 28 additional days are allowed for blood count recovery, if needed.
Interventions:
Drug: Cytarabine
Other: Placebo

Current Primary outcome:
Overall Survival in TP53 WT Population [ Time Frame: Baseline up to approximately 3.5 years ]

Current secondary outcomes:
- Overall Survival in the Overall Population [ Time Frame: Baseline up to approximately 3.5 years ]
- Percentage of Participants in CR at the End of Induction According to Hematologic Malignancy Response Assessment (HMRA) in TP53 WT Population [ Time Frame: At the end of induction (up to Day 56) ]
- Percentage of Participants in CRp at the End of Induction According to HMRA in TP53 WT Population [ Time Frame: At the end of induction (up to Day 56) ]
- Percentage of Participants with Overall Remission at the End of Induction According to HMRA in TP53 WT Population [ Time Frame: At the end of induction (up to Day 56) ]
- EFS According to HMRA in TP53 WT Population [ Time Frame: Baseline up to treatment failure, relapse or death from any cause (up to approximately 3.5 years) ]
- LFS According to HMRA in TP53 WT Population [ Time Frame: Date of remission to date of relapse or death (up to approximately 3.5 years) ]
- Percentage of Participants Undergoing HSCT Following Response, in TP53 WT Population [ Time Frame: Baseline up to approximately 3.5 years ]
- Percentage of Participants in CR at the End of Induction According to HMRA in Overall Population [ Time Frame: At the end of induction (up to Day 56) ]
- Percentage of Participants in CRp at the End of Induction According to HMRA in Overall Population [ Time Frame: At the end of induction (up to Day 56) ]
- Percentage of Participants with Overall Remission at the End of Infusion According to HMRA in Overall Population [ Time Frame: At the end of induction (up to Day 56) ]
- EFS According to HMRA in Overall Population [ Time Frame: Baseline up to treatment failure, relapse or death from any cause (up to approximately 3.5 years) ]
- LFS According to HMRA in Overall Population [ Time Frame: Date of remission to date of relapse or death (up to approximately 3.5 years) ]
- Percentage of Participants Undergoing HSCT Following Response, in Overall Population [ Time Frame: Baseline up to approximately 3.5 years ]
- Apparent Clearance (CL/F) of Idasanutlin [ Time Frame: Cycle 1: Predose (0 hour [Hr]), end of 1-3 Hr cytarabine infusion, 6 Hr postdose on Days 1, 5; Predose (0 Hr) on Day 2; at Days 8, 10; Cycle 2, 3: predose (0 Hr) on Days 2, 5 (predose/postdose: relative to idasanutlin morning dose; cycle length= 28 days) ]
- Apparent Volume of Distribution (Vd/F) of Idasanutlin [ Time Frame: Cycle 1: Predose (0 Hr), end of 1-3 Hr cytarabine infusion, 6 Hr postdose on Days 1, 5; Predose (0 Hr) on Day 2; at Days 8, 10; Cycle 2, 3: predose (0 Hr) on Days 2, 5 (predose/postdose: relative to idasanutlin morning dose; cycle length= 28 days) ]
- Maximum Concentration Observed (Cmax) of Idasanutlin [ Time Frame: Cycle 1: Predose (0 Hr), end of 1-3 Hr cytarabine infusion, 6 Hr postdose on Days 1, 5; Predose (0 Hr) on Day 2; at Days 8, 10; Cycle 2, 3: predose (0 Hr) on Days 2, 5 (predose/postdose: relative to idasanutlin morning dose; cycle length= 28 days) ]
- Steady-State Concentration (C trough) of Idasanutlin [ Time Frame: Cycle 1: Predose (0 Hr), end of 1-3 Hr cytarabine infusion, 6 Hr postdose on Days 1, 5; Predose (0 Hr) on Day 2; at Days 8, 10; Cycle 2, 3: predose (0 Hr) on Days 2, 5 (predose/postdose: relative to idasanutlin morning dose; cycle length= 28 days) ]
- Area Under the Concentration-Time Curve (AUC) During One Dosing Interval (AUCtau) of Idasanutlin [ Time Frame: Cycle 1: Predose (0 Hr), end of 1-3 Hr cytarabine infusion, 6 Hr postdose on Days 1, 5; Predose (0 Hr) on Day 2; at Days 8, 10; Cycle 2, 3: predose (0 Hr) on Days 2, 5 (predose/postdose: relative to idasanutlin morning dose; cycle length= 28 days) ]
- AUC from Time Zero to 24 Hours Post Dose (AUC0-24) of Idasanutlin [ Time Frame: Cycle 1: Predose (0 Hr), end of 1-3 Hr cytarabine infusion, 6 Hr postdose on Days 1, 5; Predose (0 Hr) on Day 2; at Days 8, 10; Cycle 2, 3: predose (0 Hr) on Days 2, 5 (predose/postdose: relative to idasanutlin morning dose; cycle length= 28 days) ]
- Half-Life (t 1/2) of Idasanutlin [ Time Frame: Cycle 1: Predose (0 Hr), end of 1-3 Hr cytarabine infusion, 6 Hr postdose on Days 1, 5; Predose (0 Hr) on Day 2; at Days 8, 10; Cycle 2, 3: predose (0 Hr) on Days 2, 5 (predose/postdose: relative to idasanutlin morning dose; cycle length= 28 days) ]
- Total Clearance (CL) of Cytarabine [ Time Frame: Cycle 1: Within 2 Hr pre-cytarabine dose, end of 1-3 Hr cytarabine infusion, 6 Hr post idasanutlin morning dose on Days 1, 5; Within 2 Hr pre-cytarabine dose on Day 2; Cycle 2, 3: Within 2 Hr pre-cytarabine dose on Day 2 (Cycle length= 28 days) ]
- Volume of Distribution (Vd) of Cytarabine [ Time Frame: Cycle 1: Within 2 Hr pre-cytarabine dose, end of 1-3 Hr cytarabine infusion, 6 Hr post idasanutlin morning dose on Days 1, 5; Within 2 Hr pre-cytarabine dose on Day 2; Cycle 2, 3: Within 2 Hr pre-cytarabine dose on Day 2 (Cycle length= 28 days) ]
- Percentage of Participants with Adverse Events [ Time Frame: Baseline up to approximately 3.5 years ]
- Change from Baseline in European Organisation for the Research and Treatment of Cancer Quality of Life Questionnaire Core 30 (EORTC QLQ-C30) Score [ Time Frame: Cycle 1 Day 1 (Baseline), Days 8, 15, 28 of Cycle 1, Days 1, 8, 15, 28 of Cycles 2, 3, 28 days after last dose (last dose on Cycle 3 Day 5), thereafter every 3 months until relapse (maximum up to 3.5 years) ]
- Change from Baseline in EuroQol 5 Dimension 5-Level (EQ-5D-5L) Questionnaire Score [ Time Frame: Cycle 1 Day 1 (Baseline), Days 8, 15, 28 of Cycle 1, Days 1, 8, 15, 28 of Cycles 2, 3, 28 days after last dose (last dose on Cycle 3 Day 5), thereafter every 3 months until relapse (maximum up to 3.5 years) ]