The European Medicines Agency has given the go-ahead for the use of GlaxoSmithKline and Genmab’s Arzerra as a treatment for refractory chronic lymphocytic leukaemia.

Arzerra (ofatumumab) was approved by regulators across the Atlantic in October last year, and yesterday GSK and Genmab confirmed that the drug has now received a conditional marketing authorisation in Europe for CLL, but only for the 25% or so of patients who have failed to respond to standard therapy with Genzyme’s Campath (alemtuzumab) or the chemotherapy fludarabine.

Conditional marketing authorisation is assigned to drugs with a positive benefit/risk profile when they address an unmet medical need and the benefits of their immediate availability outweigh the risks of not having enough data for a full approval. Under the conditions associated with this type of approval, GSK will be required to submit further data for Arzerra to the EMEA.

The drug is a monoclonal antibody that works by triggering the body’s own immune system to fight against normal and cancerous B-cells. It has a unique mode of action under which it attaches itself to the loop epitopes on a molecule called CD20, which is found on the surface of B-cells, the type of cell that becomes cancerous in CLL.

Nearly all patients with CLL ultimately relapse and it therefore remains an incurable disease, GSK noted. Patients with refractory forms of the disease have limited therapeutic options and poor outcomes, and the prognosis for patients who cannot take fludarabine and alemtuzumab is very poor, with a median survival of eight months.

"Because CLL is a disease that keeps coming back each time it is treated, extending the life of patients with the disease means finding new treatments that can work when other treatments have failed. Ofatumumab does just that, and this is what makes the drug such an important development for patients with CLL," said Professor of Haematology Andrew Pettitt, from the Liverpool Cancer Research UK Centre.

Analysts are reportedly expecting Arzerra - the rights to which GSK bought from Genmab in December 2006 - to pull in annual sales of around nearly $465 million by 2013, but the drug could be facing a setback after Roche and Biogen filed a complaint in the US early last month claiming that it infringes a patent held by their cancer drug Rituxan (rituximab).

At the time, a GSK spokeswoman told Reuters that the firm does not believe Roche and Biogen’s claims are valid or enforceable, and that the suit does not seek an injunction to prevent the actual sale of the drug.