Eli Lilly could face generic competition for attention deficit disorder medication Strattera, after a court ruling invalidated a patent that would have prevented the sale of copies until May 2017.

Eli Lilly reduced its sales forecast in response, saying it expects “near-term entry” of generic versions of the drug from the likes of Teva Pharmaceuticals and Novartis AG.

John Lecheliter, Eli Lilly chairman and CEO, said that the ruling would not cause the company to deviate from plans to maintain its dividend at its current level.

The patent loss follows a US appeals court upholding a ruling that a patent on Lilly’s cancer medicine Gemzar, which had sales of $747.4m last year, was invalid, allowing generic competition two years earlier than projected.