Blinatumomab Versus Standard of Care Chemotherapy in Patients With Relapsed or Refractory Acute Lymphoblastic Leukemia (ALL)

A Phase 3, Randomized, Open Label Study Investigating the Efficacy of the BiTE Antibody Blinatumomab Versus Standard of Care Chemotherapy in Adult Subjects With Relapsed/Refractory B-precursor Acute Lymphoblastic Leukemia (ALL) (TOWER Study)

The primary objective was to evaluate the effect of blinatumomab on overall survival when compared to standard of care (SOC) chemotherapy.

Adults with relapsed/refractory B-cell precursor ALL were randomized in a 2:1 ratio to receive blinatumomab or 1 of 4 pre-specified, investigator-chosen, SOC chemotherapy regimens. Randomization was stratified by age (< 35 years vs ≥ 35 years of age), prior salvage therapy (yes vs no), and prior allogeneic HSCT (yes vs no) as assessed at the time of consent.

The study consisted of up to a 3-week screening and pre-phase period, a treatment period consisting of induction with 2 cycles of either blinatumomab or SOC chemotherapy, a consolidation phase of up to 3 additional cycles of protocol-specified therapy, and a maintenance phase for up to an additional 12 months with protocol-specified therapy. A safety follow-up visit 30 days after the last dose of protocol-specified therapy and a long-term follow-up period were included. The long-term follow-up part of the study was discontinued prematurely based on a recommendation from the data monitoring committee (DMC) that the study be stopped for benefit.

• Subjects with Philadelphia negative B-precursor ALL, with any of the following:

  • refractory to primary induction therapy or refractory to salvage therapy,
  • in untreated first relapse with first remission duration <12 months
  • in untreated second or greater relapse
  • relapse at any time after allogeneic HSCT

• Subject has received intensive combination chemotherapy for the treatment of ALL for initial treatment or subsequent salvage therapy.

• Greater than 5% blasts in the bone marrow

• Eastern Cooperative Oncology Group (ECOG) performance status ≤ 2

Exclusion Criteria

• Malignancy other than ALL within 5 years before blinatumomab treatment, except for adequately treated selected cancers without evidence of disease
• Diagnosis of Burkitt's leukemia according to World Health Organization classification, or human immunodeficiency virus (HIV), Hepatitis B or C, or other clinically significant disorder
• Current relevant central nervous system (CNS) pathology or known or suspected CNS involvement
• Isolated extramedullary disease
• Current autoimmune disease or history of autoimmune disease with potential CNS involvement
• Autologous HSCT within 6 weeks or allogeneic HSCT within 12 weeks before blinatumomab treatment, or eligibility for allogeneic HSCT at the time of enrollment
• Active acute grade 2 to 4 graft versus host disease (GvHD) according to Glucksberg et al (1974) criteria that required systemic treatment to prevent or treat GvHD 2 weeks before blinatumomab treatment
• Known exclusion criteria to investigator choice of SOC chemotherapy (per package insert)
• Cancer chemotherapy or radiotherapy with 2 weeks, or immunotherapy (included CD19 therapy) within 4 weeks of protocol-specified therapy
• Abnormal laboratory values (alanine or aspartate transaminase [ALT or AST] or alkaline phosphatase [ALP] ≥ 5 × upper limit of normal [ULN]; total bilirubin or creatinine ≥ 1.5 × ULN), or calculated creatinine clearance < 60 mL/min.