Blinatumomab proved superior to standard chemotherapy for relapsed or refractory acute lymphoblastic leukemia (ALL), based on results of an international phase III trial reported online March 2 in the New England Journal of Medicine.
The trial was halted early when an interim analysis revealed the clear benefit with blinatumomab, Hagop Kantarjian, MD, chair of the department of leukemia, University of Texas MD Anderson Cancer Center, Houston, and his associates wrote.
The manufacturer-sponsored open-label study included 376 adults with Ph-negative B-cell precursor ALL that was either refractory to primary induction therapy or to salvage with intensive combination chemotherapy, first relapse with the first remission lasting less than 12 months, second or greater relapse, or relapse at any time after allogeneic stem cell transplantation.
Study participants were randomly assigned to receive either blinatumomab (267 patients) or the investigator’s choice of one of four protocol-defined regimens of standard chemotherapy (109 patients) and were followed at 101 medical centers in 21 countries for a median of 11 months.
For each 6-week cycle of blinatumomab therapy, patients received treatment for 4 weeks (9 mcg blinatumomab per day during week 1 of induction cycle one and 28 mcg/day thereafter, by continuous infusion) and then no treatment for 2 weeks.
Maintenance treatment with blinatumomab was given as a 4-week continuous infusion every 12 weeks.
At the interim analysis – when 75% of the total number of planned deaths for the final analysis had occurred – the monitoring committee recommended that the trial be stopped early because of the benefit observed with blinatumomab therapy. Median overall survival was significantly longer with blinatumomab (7.7 months) than with chemotherapy (4 months), with a hazard ratio for death of 0.71. The estimated survival at 6 months was 54% with blinatumomab and 39% with chemotherapy.
Remission rates also favored blinatumomab: Rates of complete remission with full hematologic recovery were 34% vs. 16% and rates of complete remission with full, partial, or incomplete hematologic recovery were 44% vs. 25%.
In addition, the median duration of remission was 7.3 months with blinatumomab and 4.6 months with chemotherapy. And 6-month estimates of event-free survival were 31% vs. 12%. These survival and remission benefits were consistent across all subgroups of patients and persisted in several sensitivity analyses, the investigators said (N Engl J Med. 2017 Mar 2. doi: 10.1056/nejmOA1609783).
A total of 24% of the patients in the blinatumomab group and 24% of the patients in the chemotherapy group underwent allogeneic stem cell transplantation, with comparable outcomes and death rates.
Serious adverse events occurred in 62% of patients receiving blinatumomab and in 45% of those receiving chemotherapy, including fatal adverse events in 19% and 17%, respectively. The fatal events were considered to be related to treatment in 3% of the blinatumomab group and in 7% of the chemotherapy group. Rates of treatment discontinuation from an adverse event were 12% and 8%, respectively.
Patient-reported health status and quality of life improved with blinatumomab but worsened with chemotherapy.
“Given the previous exposure of these patients to myelosuppressive and immunosuppressive treatments, the activity of an immune-based therapy such as blinatumomab, which depends on functioning T cells for its activity, provides encouragement that responses may be further enhanced and made durable with additional immune activation strategies,” Dr. Kantarjian and his associates noted.
Dr. Kantarjian reported receiving research support from Amgen, Pfizer, Bristol-Myers Squibb, Novartis, and ARIAD; his associates reported ties to numerous industry sources.