(Adds further detail on lawsuit, statement from Sanofi, background on EpiPen)
By Nate Raymond
April 24 (Reuters) - France's Sanofi SA on Monday sued Mylan NV, accusing the pharmaceutical company of engaging in illegal conduct to squelch competition to its EpiPen allergy treatment, which has been at the center of a public debate over drug prices.
In a lawsuit filed in federal court in Trenton, New Jersey, Sanofi said Mylan caused it to lose hundreds of millions of dollars in sales by erecting barriers to U.S. consumers' access to and use of a rival product, Auvi-Q.
In particular, Sanofi said Mylan offered rebates to insurers, pharmaceutical benefit managers and state Medicaid agencies conditioned on Auvi-Q not being an epinephrine auto-injector device they would reimburse for use by consumers.
Sanofi had introduced the Auvi-Q in 2013 to treat anaphylaxis in patients who are at risk of or have a history of the potentially fatal allergic reaction. The company ceased marketing the product in 2015 following a recall.
In a statement, Sanofi sought damages, which under U.S. antitrust law would be tripled, for Mylan's conduct in the market for epinephrine auto-injectors.
"At the time when Sanofi was marketing Auvi-Q, Mylan engaged in illegal business practices to block a new and innovative product from competing against their best-selling epinephrine auto-injector, harming customers who sought to switch to Auvi-Q and harming Sanofi," Sanofi said.
Mylan did not immediately respond to a request for comment.
The EpiPen, which Mylan acquired in 2007, is a handheld device that treats life-threatening allergic reactions by automatically injecting a dose of epinephrine.
Mylan came under fire beginning last year for raising the price of a pair of EpiPens to $600 from $100 in 2008 and listing it with Medicaid as a generic product even though it is listed with the U.S. Food and Drug Administration as a branded one.
The U.S. company, which is registered in the Netherlands, now sells a $300 generic version.
In January, Mylan said the U.S. Federal Trade Commission had opened an investigation of the EpiPen after the U.S. Senate Judiciary Committee asked the agency to look at whether it violated antitrust law.
In September, Mylan said it agreed to a $465 million settlement with the U.S. Justice Department over how the drug was classified for government buyers. The department has not confirmed the settlement. (Reporting by Nate Raymond in Boston; Editing by Lisa Von Ahn)