Swiss drugmaker Roche said that a study shows its top-selling cancer drug MabThera delayed disease progression in patients with relapsed or refractory Chronic Lymphocytic Leukaemia, or CLL.

MabThera is known as Rituxan in the United States, where it is marketed by Genetech Inc and Biogen Idec Inc. It is Roche's top-selling drug with sales of 2.9 billion Swiss francs ($2.55 billion) in the first half of 2008.

Roche said that in a global Phase III trial patients with relapsed or refractory CLL, the most common form of adult leukaemia, extended the amount of time they lived without their disease progressing when treated with MabThera in combination with chemotherapy significantly. Preliminary analysis of the safety data was in line with previous trials.