The US Food and Drug Administration has granted breakthrough therapy designation to GlaxoSmithKline and Genmab’s already-marketed leukaemia drug Arzerra as a potential first-line treatment.

The agency has concluded that Arzerra (ofatumumab) qualifies as breakthrough in combination with chlorambucil in patients with chronic lymphocytic leukaemia who have not received prior treatment and are inappropriate for fludarabine-based therapy. The designation is based on the results from a Phase III trial in more than 400 patients with previously untreated CLL.

Breakthrough therapy designation is distinct from the FDA's other fast-track programmes, such as accelerated approval and priority review, as it involves more intensive guidance from the agency on putting together an efficient drug development programme.

CLL, the most common form of leukaemia in adults, is estimated to cause more than 4,580 deaths in the USA alone in 2013. At present, no curative chemotherapy is available, GSK and Genmab note.

This is the second drug developed by Genmab to receive breakthrough therapy designation, the other being daratumumab (partnered with Johnson & Johnson) for multiple myeloma. The FDA approved Arzerra for CLL in October 2009 for patients who have not responded to Sanofi unit Genzyme’s Campath (alemtuzumab) or fludarabine.