Genetic Ablation of CD33 in HSC to Broaden the Therapeutic Index of CD33-directed Immunotherapy in Patients with AML

Key Inclusion Criteria: * confirmed AML according to the WHO classification * relapsed disease after allo-SCT from an HLA-identical family donor (≥ 2 months after allo-SCT at time of inclusion) * ≤ 29% of bone marrow blasts as detected by cytomorphology or immunohistochemistry * age ≥ 18 years * confirmed CD33 expression on leukemic blasts at current relapse (as detected by flow cytometry) * adequate organ function: * Renal function defined as: serum creatinine of ≤ 2x ULN or eGFR ≥ 30 mL/min/1.73 m2 * Liver function defined as: * ALT ≤ 3 times the ULN for the respective age * Bilirubin ≤ 2.0 mg/dl with the exception of patients with hyperbilirubinemia explained by Gilbert-Meulengracht syndrome (may be included if total bilirubin is ≤ 3.0 x ULN and direct bilirubin ≤ 1.5 x ULN) or extrahepatic disease (e.g. chronic hemolytic anemia) * Minimum level of pulmonary reserve defined as ≤ grade 1 dyspnea and pulse oxygenation \> 90% on room air * Hemodynamic stability and LVEF ≥ 40% as confirmed by echocardiogram * Absolute lymphocyte count (ALC) ≥ 100/mm3 Key Exclusion Criteria: * ECOG performance status \>2 * Confirmed CNS involvement * Acute or chronic Graft versus Host disease (GvHD) * Availability of other curative standard treatment options * Prior treatment with GO * Prior hepatic veno-occlusive disease (VOD) or sinusoidal obstruction syndrome (SOS) * Uncontrolled active hepatitis B or C * HIV-positivity * Uncontrolled bacterial, viral or fungal infection * Participation in another clinical trial at the time of screening * Organ dysfunction (liver, kidney, lung, heart) that is a contraindication for conditioning therapy * Severe concomitant disease (e.g. uncontrolled arterial hypertension, heart failure NYHA III-IV, uncontrolled diabetes mellitus, uncontrolled hyperlipidemia) * Unstable angina and/or myocardial infarction within 3 months prior to screening * Pregnant or nursing (lactating) women