Sanofi (NYSE:SNY) said yesterday that it is suing competitor Novo Nordisk (NYSE:NVO) for “misleading” marketing materials that claim Sanofi’s insulin drugs Lantus and Toujeo will be “blocked” by U.S. pharmacy benefit manager CVS Caremark in January and that patients should switch to Nordisk’s Tresiba.

CVS is replacing both Sanofi’s and Nordisk’s drugs with Eli Lilly’s Basaglar on its standard formulary, but Sanofi said that many health plans don’t follow CVS’s standard list and even those that do will probably continue to cover the company’s drugs.

“(W)e believe Novo’s statements concerning CVS Caremark’s formulary decision on Lantus and Toujeo coverage contain false and misleading claims about the continued availability of Lantus and Toujeo,” a Sanofi spokeswoman said in an emailed statement, according to Reuters. 

Nordisk has not released a formal comment on the matter.

According to the complaint filed in the U.S. District Court for the District of New Jersey, Sanofi is seeking an order to force Nordisk to pay unspecified money damages and withdraw the marketing materials.

Other insurers, such as UnitedHealth Group Inc., have put pressure on Sanofi’s U.S. diabetes business in recent months, replacing Lantus and Toujeo with the cheaper biosimilar Basaglar.

Until recently, Sanofi has been involved in talks with Actelion (VTX:ATLN) in an attempt to buy the Swiss biotech firm. Sanofi jumped at the chance to make a deal after Johnson & Johnson (NYSE:JNJ) backed out of negotiations, but recent reports confirmed that the US healthcare group has re-entered exclusive talks with Actelion, kicking Sanofi to the curb.

The French drugmaker was eager to land a deal after it lost out to Pfizer in a pursuit for Medivation earlier this year.