Gemtuzumab Ozogamicin-Containing Salvage Strategies as a Bridge to Second Allogeneic Hematopoietic Stem Cell Transplantation in Post-Transplant Relapsed AML.

Post-transplant relapsed acute myeloid leukemia (AML) carries a dismal prognosis. Whether gemtuzumab ozogamicin (GO)-containing salvage strategies can achieve sufficient disease control to facilitate second (2nd) allo-HSCT remains unclear. We retrospectively analyzed 34 patients with CD33-positive AML treated with GO-containing individualized salvage therapy and evaluated remission, transplantation outcomes, survival, and safety. The overall response rate was 61.8%, comprising morphologic remission in 20 patients (58.8%), including 1 complete remission (CR) and 19 complete remission with incomplete hematologic recovery (CRi), and partial remission in 1 patient (2.9%). Notably, 9/20 (45.0%) achieved MRD-negative CR/CRi, and 16/20 (80.0%) successfully proceeded to 2nd allo-HSCT. All but one patient initiated conditioning within 21-44 days after GO (median, 27 days). The median overall survival (OS) and leukemia-free survival (LFS) for the entire cohort were 7.6 and 6.6 months, respectively, with 1-year OS/LFS rates of 36.8%. Among CR/CRi patients, 1-year OS/LFS reached 61.9% following 2nd allo-HSCT. MRD-negative CR/CRi before transplantation was associated with superior post-transplant outcomes, with 1-year OS/LFS rates of 87.5% versus 33.3% among patients with MRD-positive CR/CRi (both P=0.012). Exploratory analysis showed numerically higher survival among patients transplanted >30 versus ≤30 days after GO (85.7% vs. 54.6%). Persistent cytopenias before conditioning were common (WBC <0.5×10⁹/L, 55.6%; platelets <20×10⁹/L, 38.9%) and did not preclude transplantation in patients achieving adequate disease control. Hepatic toxicity was generally manageable, with grade 1-2/≥3 ALT or AST elevation in 47.1%/14.7%, grade 1-2 hyperbilirubinemia in 29.4%, and only one fatal sinusoidal obstruction syndrome/veno-occlusive disease (1/18, 5.6%) after 2nd allo-HSCT. GO-containing individualized salvage strategies were associated with manageable hepatic toxicity and feasible bridging to 2nd allo-HSCT. Achieving deep remission before transplantation may be critical for improving post-transplant outcomes.