Novartis had last year filed a case for Glivec, its anti-cancer treatment, to challenge an Indian law that bans patents for modifications to old medicines, but only for drugs developed after 1995.
A court in the Indian city of Chennai on Monday dismissed a contention by Novartis that India's patent law passed in 2005 was inconsistent with World Trade Organisation rules on intellectual property rights.
However the court reserved judgement on a broader petition that challenges the India Patents Act, Press Trust of India said.
Medecins Sans Frontieres nonetheless called the court decision against Novartis "a major victory for patients' access to affordable medicines in developing countries."
"This is a huge relief for millions of patients and doctors in developing countries who depend on affordable medicines from India," said Tido von Schoen-Angerer, Director of the MSF campaign for access to essential medicines. The issue went to the heart of India's Patents Act, which stipulates that an old drug cannot be granted a new patent unless changes have made it significantly more effective.
Novartis had argued that "incremental innovations" should be patentable and claimed that the Indian law breached the country's World Trade Organisation obligations.
Critics had said a ruling in favour of the Swiss firm would have set a dangerous precedent and would have stifled global access to generic medicines - cheaper, legal copies of a branded drug for which the patent has lapsed or been lifted.
Read more:
Tutu: people not profits
Hidden cancer secrets revealed