India's patents chief ruled in March the price Bayer charged for the drug, Nexavar, was "exorbitant" and ordered the firm to give a so-called "compulsory licence" to make the medicine to Indian company Natco Pharma.

Bayer AG has challenged a ground-breaking Indian ruling that allowed a local firm to produce a vastly cheaper copy of its patented drug for kidney and liver cancer.

"We will rigorously continue to defend our intellectual property rights which are a prerequisite for bringing innovative medicines to patients," Bayer spokesman Aloke Pradhan told AFP in an emailed statement on Saturday.

The patent controller's order "damages the international patent system and endangers pharmaceutical research", Pradhan said.