Case Report: Immune-directed post-transplant maintenance with low-dose gemtuzumab ozogamicin and stepwise donor lymphocyte infusion in acute myeloid leukemia with t(1;3)(p36.3;q21).

Relapse after allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the leading cause of treatment failure in acute myeloid leukemia (AML), particularly in genetically adverse subtypes. Although prophylactic donor lymphocyte infusion (DLI) may augment graft-versus-leukemia effects, its stand-alone efficacy is suboptimal, necessitating rational combination approaches. Limited case reports have suggested potential clinical benefits of gemtuzumab ozogamicin (GO) in combination with DLI as salvage therapy for post-transplant relapse; however, its role in prophylactic maintenance has not been determined. We report a 29-year-old woman with chemo-refractory AML harboring t(1;3)(p36.3;q21) who relapsed approximately 3 months after her first allo-HSCT. She underwent a second haploidentical allo-HSCT without achieving remission beforehand. Given the extremely high risk of relapse, she received immune-directed maintenance with low-dose GO (3 mg/m2 on days 98 and 140 post-transplant) followed by dose-escalated DLI (six monthly infusions starting on day 374). Although the patient developed chronic graft-versus-host disease, including pulmonary involvement (NIH lung score 2), it remained clinically manageable. She maintained molecular complete remission for more than 6 years. Our case suggests that sequential low-dose GO followed by stepwise DLI may support durable remission when used as a post-transplant maintenance strategy in chemo-refractory AML with adverse cytogenetics, such as t(1;3)(p36.3;q21). This maintenance approach warrants further investigation to clarify feasibility and safety.