Patients’ rights advocates in India on Tuesday filed two oppositions in the Indian patent office, challenging patent claims by the US pharmaceutical company Gilead Sciences for its medicines sofosbuvir and velpatasvir, used to treat hepatitis-C infections.

The oppositions filed by the Delhi Network of Positive People (DNP+) challenge Gilead’s patent applications for the tablet formulations of the fixed dose combination of sofosbuvir and velpatasvir and a new form of velpatasvir.

The opposition is based on provisions in India’s patent laws that can deny or restrict patents on products that lack novelty, inventive steps and enhanced therapeutic efficacy, the DNP+ claimed in a media release.

The DNP+ said Gilead had launched sofosbuvir/velpatasvir in the US in 2016 at over $74,000 for a 12-week regimen. Velpatasvir is a key medicine used in combination with sofosbuvir in the oral treatment of all six major genotypes of the hepatitis-C virus, it said.

“Access to affordable generic sources of this medicine and its combination with sofosbuvir are critical for all countries with a high burden of people living with hepatitis-C,” the network said.

India’s generic drug-makers can manufacture the medicines if the patents are denied.

The international humanitarian agency Medicins Sans Frontieres (MSF) has welcomed the patent oppositions filed by DNP+, saying India plays a critical role in supplying developing countries with affordable, quality life-saving generic medicines.

“Through these patent oppositions, DNP+ aims to prevent unmerited patent applications from being granted and encourage open competition on the combination of sofosbuvir and velpatasvir after the basic compound patents have expired or are revoked in countries, excluded from Gilead’s licence agreements,” the MSF said.

Spokespersons from Gilead Sciences were not immediately available for comment on the oppositions filed by the DNP+.

Licensing pacts between Gilead and Indian generic companies enable access to lower-cost generic drugs from India to least developed countries and an increasing number of middle-income countries.

However, since South America, Russia and eastern European countries are not included in most of these pacts, their governments continue to face barriers in the import of raw materials and formulations of generic drugs, the MSF said.

In the coming decade, as the primary patents on the two drugs begin to expire in different countries, particularly in high- and middle-income countries not covered by licensing pacts, Indian companies may choose to terminate their geographically restricted pacts early and supply generics to those markets.

However, the MSF said, the secondary patent claims filed by Gilead, if granted in India, will prove to be a critical barrier to supplying affordable drugs to a number of those countries.