Unexpected toxicities when nivolumab was given as maintenance therapy following allogeneic stem cell transplantation: Toxicities with maintenance nivolumab after allogeneic stem cell transplantation

Abstract Treatment options are limited for patients with hematologic malignancies who relapse after allogeneic stem cell transplantation (allo-SCT). We conducted a pilot study to assess the tolerability and efficacy of low-dose nivolumab, a PD-1 inhibitor, as maintenance therapy after allo-SCT. Of the four patients enrolled in the study, all rapidly developed immune-related adverse events (irAE); two patients experienced serious adverse events, including grade 4 neutropenia and grade 3 autoimmune encephalopathy. As a result of these unexpected severe toxicities, the study was closed to further enrollment. Even at low doses, nivolumab maintenance in the post allo-SCT setting can cause serious irAEs beyond graft-vs-host disease, and further studies of dose and timing after allo-SCT are needed.