Roche’s Genentech unit and partner Biogen Idec are seeking approval in the USA for the cancer blockbuster Rituxan as a treatment for the most common type of adult leukaemia.

The firms have submitted two supplemental Biologics License Applications to the US Food and Drug Administration for Rituxan (rituximab) plus standard chemotherapy for people with previously untreated or treated chronic lymphocytic leukaemia. The companies will request a priority review, and if granted, “anticipate the FDA will make a decision within six months”, they said. The drug was recently approved in Europe for for use in patients with previously-untreated CLL.

The applications are based on positive results from two of the largest global Phase III clinical trials conducted in patients with CLL, Genentech says. The studies, known as CLL8 and REACH, showed that Rituxan plus standard chemotherapy for CLL extended the time patients lived compared to those receiving chemotherapy alone.

In CLL8, previously-untreated patients who received Rituxan plus chemotherapy had a 69 % improvement in progression-free survival or PFS. In REACH, patients whose cancer relapsed after previous treatment had a 54% improvement in PFS.

"There is no cure for CLL, and the primary goal of treatment is to keep the cancer from getting worse," said Cecil Pickett, Biogen's president of R&D. These data showed that Rituxan was able to extend the period of time before cancer progression by about 10 months for people with newly-diagnosed or recurrent disease, he added

Genentech’s chief medical officer, Hal Barron, noted that the results from these studies, which involved nearly 1,500 patients, “give us confidence in Rituxan's efficacy and safety in CLL". Approval will boost Rituxan’s already-considerable sales which hit $2.6 billion last year.

The drug, which is sold as MabThera by Roche outside the USA, is currently approved for non-Hodgkin’s lymphoma and rheumatoid arthritis.