Medical NGOs mounted a new legal bid Monday to break a US pharma giant's hold on a hepatitis C drug whose price -- costing thousands of dollars for a typical course -- has unleashed a fierce patent battle.

The drug, known by its lab name as sofosbuvir, cures 90 percent of Hep C cases, bringing hopes for millions infected with the dangerous liver virus. 

But critics say the manufacturer, Gilead Sciences, has priced it out of the reach of many patients and public health systems.

A single pill of the the drug, marketed as Sovaldi and other names, can cost up to $1,000 (920 euros). In France, a 12-week course of treatment costs 41,000 euros.

Seeking to clear the way for a low-cost generic version of the drug, the groups on Monday filed a fresh legal challenge with the European Patent Office in Munich.

The complaint has been backed by 30 groups from 17 European nations including Doctors Without Borders (MSF) and Doctors of the World (MDM).

"Gilead's patent monopolies on sofosbuvir are blocking access to affordable hepatitis C treatment," said Alienor Devaliere, EU Policy Advisor for MSF's Access Campaign. 

"The science behind sofosbuvir isn't new."

The new suit takes aim at the base compound used to make the drug. 

In a previous challenge last October, MDM notched up a partial victory when the European Patent Office upheld Gilead's patent but "in an amended form". The ruling protected sofosbuvir's component parts, but not the base compound itself.

In its previous legal filing, MDM had argued Gilead did not deserve the patent as the science behind the drug was not sufficiently innovative, and relied on advances made by other private and public researchers.

Hepatitis C is a liver disease caused by a blood-borne virus, transmitted for instance through infected needles. 

According to the UN's World Health Organization (WHO), between 130 and 150 million people are chronically infected with the virus -- a condition that leads to cirrhosis of the liver in 15-30 percent of cases within 20 years.

The annual death toll from Hepatitis C-related liver diseases is around 700,000 according to the WHO website.

Gilead did not immediately respond to a request to comment on the new lawsuit.

Source :Naharnet