Supply of cheap, copycat drugs for the developing world could be badly threatened if Swiss firm wins a challenge to India’s patent law, medical charity MSF said.

The warning came as the Supreme Court was due to hear more arguments in an appeal seeking patent protection.

“If the patent law challenge is successful, it would have a devastating impact on access to affordable medicines across the developing world,” said Leena Menghaney, India representative of Medecins Sans Frontieres (MSF).

The drugmaker’s challenge goes to the heart of India’s patent act, which says a patent cannot be granted for an old drug unless changes make it significantly more therapeutically effective.