Cambridge drug developer Idenix Pharmaceuticals Inc. has filed lawsuits in Europe charging that biotechnology giant Gilead Sciences Inc. infringed on an Idenix patent when it marketed a popular new hepatitis C treatment in England, France, and Germany.
The suits escalate a three-month-old legal battle between Gilead and Idenix over the drug, called Sovaldi. Idenix — in which a Boston hedge fund has taken a growing position — says it has exclusive rights to intellectual property for sofosbuvir, the compound on which Sovaldi is based. The company lodged similar complaints against Gilead in California in December.
Idenix has not specified how much it is seeking in damages. Its suits in Europe follow the granting of a patent by the European Union on Wednesday. The patents that are the subject of the US infringement cases were granted between 2005 and 2009.
“These are the first offensive moves Idenix has taken in this landscape of litigation against Gilead,” said Teri Dahlman, an Idenix spokeswoman. “We feel strongly about our intellectual property and we’re defending it.”
Amy Flood, a vice president at Gilead’s headquarters in Foster City, Calif., said her company rejects Idenix’s intellectual property assertion.
“Gilead will defend against any claim brought by Idenix and we will challenge the validity of Idenix’s European patent,” she said.
Shares of Idenix were unchanged at $6.94 on the Nasdaq exchange Friday. Gilead shares tumbled 3.8 percent to $75.05, a loss of $2.96 apiece.
Patients carrying the liver-ravaging hepatitis C virus have been gravitating to Sovaldi, approved by the Food and Drug Administration in December, because it is a pill that is easier to tolerate, can be taken for a shorter span than other treatments, and is considered more effective than previous drugs. The wholesale price of Gilead’s drug is $28,000 for a four-week treatment.
Analysts have projected Sovaldi could generate sales of at least $6 billion this year, which would make it one of the top-selling drugs of all time. Vertex Pharmaceuticals Inc., the Boston biotechnology company that markets rival hepatitis C drug Incivek, has lost business to Sovaldi and other new-generation treatments for the disease.
Idenix, founded in 1998, co-developed a hepatitis B treatment currently marketed exclusively by Novartis AG, the Swiss pharmaceutical company that has its worldwide research and development headquarters in Cambridge. Idenix has two hepatitis C drug candidates in clinical trials, and several others in preclinical development, drawing on intellectual property it has under patents awarded in the United States and Europe.
In a regulatory filing last month, Boston’s largest hedge fund, Seth Klarman’s Baupost Group, said it had accumulated a 35.4 percent stake in Idenix.Robert Weisman can be reached at email@example.com. Follow him on Twitter @GlobeRobW.