International health advocacy groups Médecins Sans Frontières (MSF) and Médecins du Monde (MdM) have launched a fresh challenge to the patent on Gilead Sciences’ hepatitis C virus (HCV) drug sofosbuvir in Europe, Reuters reports.

The challenge, recently presented to the European Patent Office, argues that the science behind sofosbuvir (brand name: Sovaldi) is not new and accuses Gilead of abusing its patent on the next-generation treatment. Campaigners also argue that the patent on the popular treatment (which costs tens of thousands of dollars in Europe) has made HCV cures unnecessarily expensive and therefore unattainable for thousands of patients. 

MSF (known in the United States as Doctors Without Borders) and MdM, which have been joined by 28 groups across Europe in the challenge, also noted that key patents on sofosbuvir have already been revoked in China and Ukraine and that decisions are pending in several other countries, including Argentina, India, Brazil, Russia and Thailand.

If successful, the revocation of Gilead’s patent could make cheaper generic versions of sofosbuvir available in Europe — which advocates say would dramatically increase access to treatment across the continent.

This is the second time since 2015 that MdM has accused Gilead of abusing its patent on sofosbuvir. MSF has also filed similar challenges against Gilead in several countries. 

In response, Gilead said it was working to ensure that patients had access to its hepatitis C drugs and reminded the groups that the company’s treatment has so far cured more people in the past two and a half years than were cured in the previous 20 years combined.