Salvage Therapy With Inotuzumab Ozogamicin in Relapsed/Refractory B‐ <scp>ALL</scp> After <scp>CAR</scp> ‐T Therapy and <scp>HSCT</scp> : A Case Series

BACKGROUND: Although inotuzumab ozogamicin (InO) has been approved as an effective agent for patients with refractory/relapsed (r/r) B-cell acute lymphoblastic leukemia (B-ALL), data in the context of post chimeric antigen receptor (CAR)-T cell therapy and allogeneic hematopoietic stem cell transplantation (allo-HSCT) relapse are lacking. CASE: We report on a series of three heavily pretreated r/r B-ALL patients who relapsed after CAR-T therapy and allo-HSCT and were salvage treated with InO. All achieved bone marrow (BM) remission with negative minimal residual disease (MRD) after the first InO cycle; of note, one patient with extensive extramedullary involvement before InO treatment experienced a remarkable tumor regression on PET/CT imaging. They all completed 2 cycles of InO. Two patients experienced relapse 8 and 9.5 months after InO initiation (one central nervous system relapse, the other breast relapse). Treatment-related adverse events (AEs) were primarily hematologic and manageable. Crucially, no sinusoidal obstruction syndrome (SOS) developed in any of the patients during the whole course of InO therapy and beyond. CONCLUSION: InO appears to be a promising and well-tolerated salvage regimen for inducing remission in heavily pretreated B-ALL patients who have relapsed after both CAR-T therapy and allo-HSCT.