In a duo of setbacks Mylan has received an FDA warning over manufacturing concerns at three of its Indian plants, and is being sued by Janssen after filing its generic Zytiga with the regulator.

The FDA’s warnings concern three facilities that Mylan acquired when it bought Indian sterile injectables firm Agila Specialities for $1.75 billion in 2013.

The regulator investigated two of these plants in 2014 and one in early 2015 and found “significant violations of current good manufacturing practice”, several of which are said to be “recurrent and long-standing”.  Among these were the failure to follow procedures designed to prevent contamination of drugs that are purported to be sterile.

The FDA says that since then, Mylan’s responses have lacked sufficient corrective action, and that if the firm fails to correct these violations it may block products from these plants being sold in the US.

In a statement, Mylan’s CEO Heather Bresch says: "We have a deep and unwavering commitment to quality everywhere we operate. We have been and will continue to work diligently to address all of the FDA's observations and have made important progress."

The statement adds that the FDA’s actions have no material impact on Mylan's business or its full year earnings guidance.

Zytiga lawsuit

Mylan has also confirmed that it is being sued Janssen in the US after filing an NDA for its generic version of the company’s prostate cancer drug Zytiga.

Abiraterone acetate, the active ingredient in Zytiga, was developed by Cancer Research UK, who assigned the commercialisation rights to Cougar Biotechnology. Johnson & Johnson acquired Cougar in 2009 and began selling Zytiga as a commercial product in 2011. Its designation as a New Chemical Entity is set to expire in 2016.

Mylan believes that it is one of the first companies to have filed a generic NDA for the drug and may therefore be eligible to 180 days of exclusivity under US rules.

Last year, Zytiga had US sales of approximately $1.08 billion, according to IMS health.