GlaxoSmithKline and Genmab are a big step closer to expanding the patient population for their leukaemia drug Arzerra, after filing the drug with US regulators as a first-line treatment for a certain form of the disease.

The drugmakers said they have now submitted a supplemental Biologics License Application to the US Food and Drug Administration seeking approval for its use in combination with an alkylator-based therapy in patients with chronic lymphocytic leukaemia (CLL) who have not received prior treatment.

The application is based on Phase III findings (full details of which are to be presented in December) showing that patients taking Arzerra (ofatumumab) and chlorambucil experienced a 9.3 month improvement in progression free survival (PFS) compared to patients taking chlorambucil alone (22.4 months versus 13.1 months, respectively).    

Given that there were no unexpected safety findings the drug hit the key target of first-line CLL treatment - maximising the time patients live without their disease progressing while keeping side effects as low as possible.

Arzerra is a monoclonal antibody that causes the body’s immune response to fight against normal and cancerous B-cells. It attaches to the small and large loop epitopes – on a molecule called CD20, which is found on the surface of B-cells, the type of cell which becomes cancerous in CLL.

The drug was given a green light by the FDA in 2009 treatment for CLL patients who have not responded to Genzyme Corp’s Campath (alemtuzumab) or the chemotherapy fludarabine, and was also recently awarded 'breakthrough therapy' status by the regulator as a first-line treatment for the disease.