Genentech, a unit of pharmaceutical giant Roche AG (RHHBY), filed a lawsuit claiming Amgen Inc. (AMGN) withheld key information about its proposed biosimilar of Genentech's cancer drug Avastin that could potentially spur patent infringement litigation.

Avastin (bevacizumab) is one of Genentech's blockbuster cancer drugs. It was first approved in February 2004, and has since then secured nine different approvals from the Food And Drug Administration (FDA) to treat colorectal, breast, lung, kidney, cervical and ovarian cancer.

The multiple-indication drug clocked around $6.8 billion in total sales in 2016. Avastin is facing imminent competition from Amgen’s proposed biosimilar named ABP 215. Amgen and its partner Allergan PLC (AGN) submitted a Biologics License Application (BLA) to the FDA in November 2016. (For more, see Amgen, Allergan Unveil Avastin Copycat.)

The FDA accepted their application in January 2017. Under the Biologics Price Competition and Innovation Act (BPCIA), the originator, Genentech, has 60 days for expert review and claim for any possible patent infringements. BPCIA rules require that a new applicant should provide “information that describes the process or processes used to manufacture the biological product.”

Genentech claims Amgen only submitted its application and did not provide FDA-required details. Genentech wants the court to compel Amgen to provides all the necessary data Genentech needs, as well as allow Genentech’s expert assessment, and put forth new deadlines for resolving any possible disputes arising from patent infringements.

The filing cited Amgen’s attempts to block a biosimilar rival of its anemia drug Epogen, when Amgen sued Hospira Inc., which is owned by Pfizer Inc. (PFE), for non-compliance with the BPCIA. Roche also wants to bar Amgen from selling its biosimilar to Avastin until the legal battle clears. (For more, see Amgen Targeting Biosimilars.)

With time running out for Roche to fend off biosimilar competition, a patent battle may be the much-needed respite for saving the sales of one of its best-selling drugs. (See also, Biosimilar Drug Competition Heats Up in 2017.)