Follicular lymphoma is considered incurable and relapse is common. It is estimated that more than 75,000 people are diagnosed with this most common form of non-Hodgkin lymphoma each year worldwide, Roche said.
Investors have long fretted that biosimilars will eventually eat into Roche's business, which is heavily biased towards biological medicines that have so far been relatively immune to copycat competition.
That competitive landscape is now changing with the arrival of biosimilars, which are approved by regulators as similar enough to do the job, even if they are not 100 percent identical due to different production processes.
Roche is also continuing to study Gazyva in other clinical studies, including a closely watched trial called GOYA, which analysts had expected to produce results ahead of the GALLIUM one that reported on Friday.
Follow CNBC International on Twitter and Facebook.