US regulators approved Amgen's blinatumomab — a CD19- and CD3-targeting bispecific antibody — for acute B-cell lymphoblastic leukaemia, 5 months ahead of schedule.

The lowdown: The US Food and Drug Administration's accelerated approval of Amgen's breakthrough designee blinatumomab marks the first US approval for a bispecific antibody. The bispecific T-cell engager (BiTE) immunotherapy binds CD19 on the surface of B-cell lymphoblasts and CD3 on the surface of T cells, bringing the cell types together and driving an immune response to malignant cells. In clinical trials in 185 adults with acute B-cell lymphoblastic leukaemia (B-ALL), 32% of treated patients had complete remissions for an average of 6.7 months.

Blinatumomab and the BiTE technology were initially developed by Micromet, which was acquired by Amgen in 2012 for US$1.16 billion. Financial analysts expect sales of over $300 million for the bispecific by 2019, according to Thomson Reuters Cortellis. Uptake of blinatumomab may be limited by competition from other exciting drugs in the ALL pipeline, including Pfizer's antibody–drug conjugate inotuzumab ozogamicin and Novartis' Phase II personalized cell therapy CTL019. Blinatumomab's administration route (it is continuously infused with a portable mini-pump for 28 days, and so requires visits to the hospital every 48 hours to change infusion bags) and adverse events (including neurotoxicity and symptoms of cytokine-release syndrome) may also keep sales down.

Blinatumomab leads an explosion of the bispecific antibody pipeline. At least 18 other bispecifics are in clinical development for oncology, autoimmune and infectious-disease indications (Nature Rev. Drug Discov. 13, 799–801; 2014). Trion Pharma secured European approval for a first (rat–mouse hybrid) bispecific in 2009, but the newer bispecific antibody formats that now fill the pipeline are more stable, less immunogenic and easier to manufacture.