Background: Background: Acute Myeloid Leukemias arising after cytotoxic therapy (t-AML) or with myelodysplasia-related changes (AML-MRC) share adverse risk features and poor outcomes after standard 3+7 chemotherapy. In a randomized clinical trial, CPX-351 has shown superior overall survival (OS) compared to standard anthracyclinecytarabine schedule in these AML subtypes. Aims:Aims: to evaluate the effectiveness of CPX-351 treatment in a real-world setting. Methods:Methods: adult t-AML and AML-MRC patients who have been treated upfront with CPX-351 in 35 Spanish centers between 2018 and 2021. All patients were included in the PETHEMA registry (NCT02606825). Primary end-point was OS. Secondary end points were complete remission with or without hematological recovery (CR/CRi), proportion of minimal residual negativity (MRD), rate of allogeneic hematopoietic stem cell transplant (HSCT) and safety. Results: Results:CPX-351 was administered to 74 patients as first induction chemotherapy. Median age was 67 (63-71) years, with 40% (30/74) of female patients. ECOG performance status score was 0-1 in 85% (53/62) patients. A diagnosis of t-

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