Roche’s new blood cancer drug Gazyva has failed to show significant improvements in a late-stage lymphoma trial, delivering a blow to its plans for a successor to blockbuster drug Rituxan. Results of a Phase III study, which assessed Gazyva in patients with previously untreated diffuse large B-cell lymphoma, showed that the new drug did not perform any better than its older therapy Rituxan.

The Swiss drugmaker was hoping to repeat findings from two previous studies that showed the drug boosted survival rates in patients with previously untreated follicular lymphoma or chronic lymphocytic leukemia compared to Rituxan, when each was combined with chemotherapy.

The findings have stymied Roche’s plans for Gazyva which it hoped would help defended its position in treating blood cancers when Rituxan starts to face competition from cut-price copycat drugs, or biosimilars, possibly in the latter half of 2017. Patent protection for Rituxan has already expired in Europe, and will run out in the US in 2018, with a likely fall in revenue after 2018. Rituxan is Roche’s third-biggest drug with revenues of 5.6 billion Swiss francs last year.

The race to launch its successor is said to be symptomatic of the broader challenge Roche faces from the rise of other biosimilars. Several manufacturers are said to be working on copies of Rituxan, Herceptin – Roche’s blockbuster breast cancer drug which had sales of 6.5 billion Swiss francs in 2015 – and Avastin which loses US patent protection in 2019.

Roche said it is carrying out additional studies investigating Gazyva across a range of blood cancers in combination with other medicines, including cancer immunotherapies and small molecule inhibitors.