Background: Gemtuzumab ozogamicin (GO) is a CD33-directed antibody-drug conjugate approved by the FDA in 2017 for the treatment of newly diagnosed and relapsed/refractory (R/R) CD33-positive acute myeloid leukemia (AML) in adults and pediatric patients of 1 month and older and 2 years and older, respectively. Previous data have associated GO with adverse events (AEs) including hepatotoxicity and hepatic veno-occlusive disease (VOD). Patients receiving allogeneic hematopoietic stem cell transplantation (HSCT) may be at greater risk of VOD with GO. This study aimed to characterize AEs after HSCT in adult patients with AML who were treated with GO. Methods: This non-interventional post-authorization safety study used de-identified healthcare data from the Center for International Blood and Marrow Transplant Research (CIBMTR) database. Data were collected from 01 September 2017. Safety outcomes post-HSCT were evaluated in adult patients with newly diagnosed or R/R AML who received GO prior to first HSCT. Data cutoff was 04 July 2023. Results: We present the interim data of 157 patients from 24 centers with a median follow-up of 12.9 months (range, 3.0-49.7). At the time of HSCT, 84 patients were in first complete remission (CR1), 48 patients were in second CR (CR2) and 25 patients were in third or greater CR, relapse or primary induction failure (CR3, n=5; Rel, n=12; PIF, n=8). Most patients (n=105; 67%) received GO as first line therapy. Median lines of therapy prior to HSCT were 2, 3.5 and 5 in CR1, CR2 and CR3/Rel/PIF groups, respectively. Median age was 52.5 y (range, 18.7-74.9); 53% male. Time from diagnosis to first GO dose was <3 months for most patients (n=120; 76%). Total cumulative GO dose was 1-3 mg/m2 in 25 (16%), 4-6 mg/m2 in 28 (18%), 7-9 mg/m2 in 45 (29%) and ≥10 mg/m2 in 14 (9%) patients. The most common HSCT donor type was unrelated (n=93; 59%), and 55% of patients received myeloablative conditioning regimens. Non-fatal VOD was reported in 7 (4%) patients. Median time from HSCT to VOD was 0.9 months (range, 0.4-2.2). No VOD-related deaths occurred. Outcome probabilities for 6-month transplant-related mortality (TRM) were 8% (95% CI, 4-13) and 5% (95% CI, 2-8) for 100-day VOD. Conclusions: The use of GO appears to be safe prior to HSCT in adults with AML. Rates for 100-day VOD and TRM were comparable to those previously reported for patients with AML who received HSCT with or without prior GO. Clinical trial information: B1767034.