Confirmatory open-label, single-arm, multicenter phase 2 study of the BiTE antibody, Blinatumomab in patients (pts) with relapsed/refractory B-precursor acute lymphoblastic leukemia (r/r ALL)

SUMMARY: The FDA on December 3, 2014, granted accelerated approval to BLINCYTO® (Blinatumomab), a bispecific T cell engager (BiTE) antibody, for treatment of Philadelphia chromosome-negative (Ph-) Relapsed or Refractory B- cell precursor Acute Lymphoblastic Leukemia (ALL). BiTE® technology engages the body's immune system to detect and target malignant cells. These modified antibodies are designed to engage two different targets simultaneously, thereby placing the T cells within reach of the targeted cancer cell and facilitating apoptosis of the cancer cell. BiTE® antibodies are currently being investigated to treat a wide variety of malignancies. BLINCYTO® (Blinatumomab) is an investigational BiTE® antibody designed to direct the patients T cells against CD19, a protein found on the surface of B-cell derived leukemias and lymphomas. The approval was based on a multicenter single-arm phase II trial in which 185 patients with Relapsed or Refractory Philadelphia chromosome negative ALL patients were enrolled. The median age was 39 years, and patients had their 1st relapse and were refractory to post hematopoietic stem cell transplantation less than 12 months before. About a third of the patients had at least 2 salvage therapies. BLINCYTO® was given by continuous IV infusion, 4 weeks on and 2 weeks off for up to 5 cycles and the median number of cycles given were 2. The primary endpoint was complete remission (CR) and response with a reduction in Minimal Residual Disease (MRD) to less than 10^-4 or CR with partial hematological recovery (CRh), within the first 2 cycles of treatment. It was noted that 32% of patients attained CR with 2 cycles of treatment with BLINCYTO® and these responses were durable (median 6.7 months). Further, 31% of the patients in this study had a CR with or without complete hematological recovery but with reduction in MRD to less than 10^-4. At the time of primary analysis, 80% of responses occurred within cycle 1. Further, the Complete Remissions (CR) and CR with partial hematological recovery (CRh) were seen in all subgroups of patients, although this was more pronounced in those with less than 50% bone marrow blasts. The median Relapse Free Survival and Overall survival were 5.9 months and 6.1 months respectively. The most frequent grade 3 adverse events were febrile neutropenia, neutropenia and anemia, occurring in 26%, 15% and 15% of patients, respectively. The authors concluded that BLINCYTO® has significant single agent antileukemia activity in a difficult-to-treat population with Relapsed and Refractory Acute Lymphoblastic Leukemia. Future studies will hopefully address whether BLINCYTO® can serve as a bridge to transplantation, in patients with Relapsed and Refractory B-cell ALL. Cytokine Release Syndrome can result from the activation of the immune system. The FDA approved BLINCYTO® with a Risk Evaluation and Mitigation Strategy (REMS). Topp MS, Goekbuget N, Stein AS, et al. J Clin Oncol 32:5s, 2014 (suppl; abstr 7005)