Blinatumomab or Inotuzumab Ozogamicin as Bridge to Allogeneic Stem Cell Transplantation for Relapsed or Refractory B-lineage Acute Lymphoblastic Leukemia: A Retrospective Single-Center Analysis

Background Blinatumomab and inotuzumab ozogamicin are now widely used to treat relapsed or refractory B-cell acute lymphoblastic leukemia (r/r B-ALL). Patients and Methods We have reported the clinical course of 34 adult patients with r/r B-ALL receiving blinatumomab or inotuzumab ozogamicin at our institution from 2009 to 2019. Results Blinatumomab-based salvage therapy was applied for overt r/r B-ALL (n = 13) or minimal residual disease (MRD) positivity (n = 5). Of the 13 patients with r/r B-ALL, 9 (69%; 95% confidence interval [CI], 39%-91%) achieved complete remission (CR), with 78% of CR patients (95% CI, 40%-97%) reaching MRD negativity. MRD negativity was also achieved in all 5 patients treated for MRD positivity. The 1-year overall survival of patients receiving blinatumomab for r/r B-ALL and MRD positivity was 54% (n = 13; 95% CI, 26%-81%) and 80% (n = 5; 95% CI, 44-100), respectively. In the inotuzumab ozogamicin group, all 16 patients were treated for overt r/r B-ALL. The rate of CR was 94% (95% CI, 70%-100%), with 67% (95% CI, 38%-88%) of CR patients reaching MRD negativity. The 1-year OS after the first application of inotuzumab ozogamicin was 46% (95% CI, 18%-74%). Of those patients receiving blinatumomab and inotuzumab ozogamicin as a bridge-to-transplant strategy, 79% and 80%, respectively, proceeded to allogeneic stem cell transplantation. The most frequent drug-specific adverse events were similar to those previously reported, including cytokine release syndrome, capillary leak syndrome, and neurotoxicity for blinatumomab and transplant-associated veno-occlusive disease of the liver for inotuzumab ozogamicin. Conclusion Together with previous observations from phase III clinical trials, these data suggest that blinatumomab and inotuzumab ozogamicin are highly effective salvage regimens in r/r B-ALL.