Pfizer Sues Alkem to Block Copies of Blockbuster Xeljanz Drug

Pfizer Inc. asked a federal court in Delaware to block copies of blockbuster arthritis drug Xeljanz proposed by Alkem Laboratories Ltd. that it said infringe a patent expiring this year.

Alkem’s generic versions of Xeljanz’s 5- and 10-milligram tablets infringe US Patent No. RE41,783, according to a complaint filed Dec. 30 in the US District Court for the District of Delaware. Xeljanz, whose active ingredient is tofacitinib citrate, also comes in 11- and 22-mg extended-release tablets and as an oral solution, but those formulations aren’t subjects of Pfizer’s suit.

• The patent, which expires Dec. 8, 2025, is the only ...