Sanofi is pursuing another US competitor for alleged breach of the patent for its top-selling diabetes drug insulin glargine (branded as Lantus and Lantus SoloStar), which together generate sales revenue of €7 billion annually. Its two versions of the drug listed in the FDA Orange Book are said to carry expiration dates ranging from 20 23 to 2028,

In a 67-page lawsuit filed in federal court in the state of New Jersey in late October, the French drugmaker has accused US generics producer Mylan of infringing 18 of its patents. Sanofi said it had decided to launch legal proceedings after out-of-court negotiations aimed at obtaining more information about the challenger’s product proved unsuccessful.

Mylan revealed earlier it had filed a New Drug Application (NDA) with the US Food and Drug Administration (FDA) for insulin glargine pre-filled pen and vial drug products. It added that its NDA included a paragraph IV certification challenging all of the Sanofi’s patents listed in the Orange Book.

According to Sanofi's lawsuit, Mylan is working together with Biocon. The biotech firm’s  insulin plant in Malaysia won approval from the EU, where the two companies are also seeking approval to launch the drug, and Biocon has already won approval for its Lantus copy in Japan.

In August, Sanofi filed a patent infringement suit against US Merck in the same New Jersey court after that company in June announced it had filed an NDA for a Lantus competitor.  Merck is said to be barred from launching its drug in the US until 2019, due to a 30-month stay under the Hatch-Waxman Act that began just over a year ago. However, it could be launched earlier if Sanofi loses any of the challenges.

After reaching a settlement with Sanofi in 2015, US drugmaker Eli Lilly in late 2016 introduced Basaglar, its cheaper biosimilar version.  In Its third quarter earnings statement, Lilly said Basaglar had generated sales of $278 million thus far. 

With only one marketed rival product so far, analysts said discounting to the Lantus brand has remained limited. If a third or a fourth player were to enter the market, Sanofi’s revenues could plunge.

According to the pharmaceutical trade journal Fierce Pharma, US drug formularies CVS and United Health meanwhile have removed Lantus from their offering and replaced it with the Lilly product, but Sanofi said it had signed contracts with the “vast majority” of US formularies for 2018.