Study for Patients With Newly Diagnosed, High-risk Acute Promyelocytic Leukemia

Inclusion Criteria: * Informed consent * Women or men with a newly diagnosed APL by cytomorphology, confirmed by molecular analysis\* * Age ≥ 18 and ≤ 65 years * ECOG performance status 0-3 * WBC at diagnosis \> 10 GPt/l * Serum total bilirubin ≤ 3.0 mg/dl (≤ 51 µmol/l) * Serum creatinine ≤ 3.0 mg/dl (≤ 260 µmol/l) * Women must fulfill at least one of the following criteria in order to be eligible for trial inclusion: * Post-menopausal (12 months of natural amenorrhea or 6 months of amenorrhea with Serum FSH \> 40 U/ml) * Postoperative (i.e. 6 weeks) after bilateral ovariectomy with or without hysterectomy * Continuous and correct application of a contraception method with a Pearl Index of \<1% (e.g. implants, depots, oral contraceptives, -intrauterine device - IUD) * Sexual abstinence * Vasectomy of the sexual partner * The confirmation of diagnosis at genetic level (microspeckled PML nuclear distribution by PGM3 monoclonal antibody and/or PML/RARa fusion by RT-PCR or fluorescence in situ hybridization (FISH) and/or demonstration of t(15;17) at karyotyping) will be mandatory for patient eligibility. However, in order to avoid delay in treatment initiation, patients can be randomized on the basis of morphologic diagnosis only and before the results of genetic tests are available Exclusion Criteria: * Patients who are not eligible for chemotherapy as per discretion of the treating physician * APL secondary to previous radio- or chemotherapy for non-APL disease * Other active malignancy at time of study entry (exception: basal-cell carcinoma) * Lack of diagnostic confirmation at genetic level * Significant arrhythmias, ECG abnormalities: * Congenital long QT syndrome; * History or presence of significant ventricular or atrial tachyarrhythmia; * Clinically significant resting bradycardia (\<50 beats per minute) * QTc \>500msec on screening ECG for both genders (using the QTcF formula detailed on protocol) * Right bundle branch block plus left anterior hemiblock, bifascicular block * Other cardiac contraindications for intensive chemotherapy (L-VEF \<50%) * Uncontrolled, life-threatening infections * Severe non controlled pulmonary or cardiac disease * Severe hepatic or renal dysfunction * HIV and/or active hepatitis C infection * Pregnant or breast-feeding patients * Allergy to trial medication or excipients in study medication * Substance abuse; medical, psychological or social conditions that may interfere with the patients participation in the study or evaluation of the study results * Use of other investigational drugs at the time of enrolment or within 30 days before study entry