B-cell Acute lymphoblastic leukemia (B-ALL) is a potentially curable malignancy in the pediatric population. In contrast, the outcomes of adults with B-ALL have remained historically poor due to risk of relapse after frontline therapy. Novel agents in the current era have changed the treatment landscape of adults with relapsed/refractory B-ALL with improved tolerability and better outcomes \[1\]. Currently, blinatumomab (CD3-CD19 bispecific molecule) and inotuzumab (CD22 antibody drug conjugate) are approved for the management of patients with relapsed/refractory B-ALL. With the superior efficacy of these agents, recent clinical trials have focused on incorporating them in the management of newly diagnosed B-ALL.
A phase 3 randomized clinical trial (E1910) has recently demonstrated the superiority of adding blinatumomab during consolidation for patients who have achieved MRD negative CR \[2\]. Patients between the ages of 30 and 70 with newly diagnosed BCR-ABL1 negative B-ALL were enrolled and initially received 2.5 months of combination induction chemo utilizing a BFM-like regimen adapted from the E2993/UKALLXII clinical trial with extended remission induction, addition of pegasparginase for patients \<55 years of age and addition of rituximab for CD20 positive patients. Subsequently, their remission and MRD status were determined centrally by 6-color flow cytometry with MRD negativity defined as \<0.01%. All patients were then randomized to receive an additional four cycles of consolidation chemo or two cycles of blin for 28 days each cycle followed by 3 cycles of consolidation chemo, another 4-week cycle of blinatumomab (3rd cycle of blinatumomab) followed by an additional cycle of chemo and then a 4th cycle of blinatumomab. Two hundred and twenty-four MRD negative patients were randomized, 112 pts to each arm. Among the MRD negative patients, superior overall survival was seen in patients who received blinatumomab (median OS: not reached vs. 71.4 months; Hazard ratio 0.42, 95% CI: 0.24 - 0.75; two-sided p=0.003) with a median follow-up of 43 months.
While the results are encouraging and practice changing to consider adding blinatumomab to MRD negative CR patients, the backbone chemotherapy regimen used in E1910 study is not a commonly used regimen in clinical practice. Due to the unmet need, physicians are often considering combining blinatumomab consolidation with several other commonly used chemotherapy regimens. However, the outcome in this setting remains unknown. Our goal in this study is to evaluate the real-world utilization of blinatumomab in the frontline setting for management of B-ALL in the United States.
