(Reuters) – Orexigen Therapeutics Inc and partner Takeda Pharmaceutical Co Ltd said they had filed a lawsuit against Actavis Plc to block a generic version of diet-pill Contrave. The lawsuit, filed at a Delaware district court, alleges that Actavis has infringed patents on Orexigen and Takeda’s weight-loss treatment. Contrave is one of the three weight-loss pills that were expected to gain quick ground in the market to reduce body weight in obese patients.