PD-1 inhibitor in patients with minimal residual disease who failed donor lymphocyte infusion or interferon after allogeneic haematopoietic stem cell transplantation.

This study aimed to evaluate the efficacy and safety of programmed death receptor 1 (PD-1) antibody in patients with acute myeloid leukaemia (AML) or myelodysplastic syndrome (MDS) with minimal residual disease (MRD) after allogeneic haematopoietic stem cell transplantation (allo-HSCT). Six patients were retrospectively reviewed in this study, and all had failed prior treatment (donor lymphocyte infusion or interferon) before PD-1 antibody administration. Among these 6 patients, two received PD-1 alone while four received PD-1 plus azacitidine. The median treatment with the PD-1 antibody was four doses (range, 1-7 doses). Three patients developed > grade 3 toxicity, including 2 deaths. Among the five evaluable patients, four achieved negative MRD with a median time to response of 2 months (range: 1-3 months); and the median duration of response was 105 days (range: 26-211 days). The median survival time of the five patients was 320 days (range: 107-350 days). Our data suggest that anti-PD-1 antibody in AML/MDS patients with positive MRD following allo-HSCT may be a treatment option.