Swiss drugmaker Roche said trials showed its new blood cancer drug Gazyva failed to deliver significant improvements over an older medicine in people with an aggressive type of blood cancer, a blow in its fight against competition from biosimilars.

Gazyva did not significantly reduce the risk of disease worsening or death for people with previously untreated diffuse large B-cell lymphoma, over current drug Rituxan in a phase III GOYA study, Roche said.

Diffuse large B-cell lymphoma is the most common form of non-Hodgkin's lymphoma. An estimated 25,000 new U.S. cases of the aggressive blood cancer, and 10,000 deaths from it, are seen each year.

"Two previous studies showed Gazyva/Gazyvaro helped people with previously untreated follicular lymphoma or chronic lymphocytic leukemia live longer without their disease worsening compared to MabThera/Rituxan, when each was combined with chemotherapy," Roche's Chief Medical Officer Sandra Horning said.

"We were hopeful we could show a similar result for people with diffuse large B-cell lymphoma and once again improve on the standard of care."

The study included 1,418 previously untreated patients.

Clinical trials with the new drug are important in deciding how well the Swiss company is placed to fend off cheaper competition from so-called biosimilar copies of Rituxan, which are likely to hit the market in the next couple of years.

Strong results with Gazyva mean Roche can argue that its new drug delivers better results for patients, even if it is more expensive than biosimilars.

Roche's shares were boosted in May after Gazyva proved significantly better than Rituxan at delaying disease progression in people with previously untreated follicular lymphoma, and Chief Executive Severin Schwan said he could "sleep better" after the win for Roche.