Background: tAML may occur as a late complication of cytotoxic therapy and is associated with a poor prognosis. CPX-351 is a liposomal formulation that delivers a synergistic 5:1 molar ratio of cytarabine (C) and daunorubicin (D). In a randomized, open-label, controlled phase III trial in patients (pts) aged 60-75 years with newly diagnosed, secondary AML (tAML or after MDS), CPX-351 significantly improved OS versus 7+3. The current analysis of this phase III study evaluated outcomes in the subgroup of pts with tAML. Methods: Pts were randomized 1:1 to induction with 1-2 cycles of CPX-351 (100 u/m² [C 100 mg/m² + D 44 mg/m²] on Days 1, 3, and 5 [2nd induction: Days 1 and 3]) or 7+3 (C 100 mg/m²/day x 7 days [2nd induction: x 5 days] + D 60 mg/m²on Days 1, 2, and 3 [2nd induction: Days 1 and 2]). Pts with complete remission (CR) or CR with incomplete platelet or neutrophil recovery (CRi) could receive up to 2 cycles of consolidation therapy. The study was not powered for this subgroup analysis. Results: 304 pts were enrolled and received study treatment, including 62 (20%) pts with tAML; demographics of tAML pts were similar between study arms. Pts with tAML had typically received prior non-anthracycline chemotherapy alone (25%), radiation alone (25%), or non-anthracycline chemotherapy + radiation (32%). CPX-351 was associated with an OS benefit versus 7+3 in older tAML pts and numerically longer event-free survival (EFS) and remission duration (Table). A greater proportion of tAML pts achieved CR+CRi (47% vs 36%, respectively) and proceeded to stem cell transplantation (37% vs 27%) with CPX-351. The safety profile of CPX-351 was comparable to that of 7+3. Conclusions: CPX-351 is associated with improved outcomes in older pts with newly diagnosed tAML. Outcomes in the tAML subgroup mirrored the overall study population, indicating CPX-351 may represent a new therapeutic option for this difficult to treat population. Clinical trial information: NCT01696084