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Amid increasing concerns and questions about the side effects of Xeljanz, which has recently been linked to reports of cancer, heart problems and pulmonary embolism, Pfizer has filed a lawsuit against two generic drug makers to prevent copies of the blockbuster drug from hitting the market.
In a complaint (PDF) filed in the U.S. District Court for the District of Delaware on February 16, Pfizer indicates attempts by Zydus Pharmaceuticals Inc. and Cadila Healthcare Ltd. to introduce generic Xeljanz 22mg extended release equivalents infringes on exclusive patent rights which continue until at least March 2023, and possibly December 2025.
Xeljanz (tofacitinib) was the first Janus kinase inhibitor (jakinib) approved by the FDA in 2012, for treatment of adults with rheumatoid arthritis, which is an autoimmune disorder that causes inflammation of the joints in approximately 1% of the population. In 2018, the drug gained approval from the FDA to treat a serious inflammatory condition called ulcerative colitis, which typically involves higher doses of 10 milligrams twice daily, or one 21 milligram extended release tablet.
According to lawsuit, Zydus infringed on Pfizer’s patent for Xeljanz when it attempted to seek approval from the FDA to sell generic copies of the drug’s active ingredient, tofacitinib citrate.
Higher doses of Xeljanz have been linked to a risk of pulmonary embolism, leading the FDA to add new label warnings in 2019. However, just before this patent lawsuit was filed, the FDA issued a new safety communication about the potential cancer risks from Xeljanz, following an initial analysis of postmarketing trial data that suggested users may face cancer and cardiovascular problems.
Additional concerns raised in the initial clinical trials suggested patients taking Xeljanz were at an increased risk for developing serious infections including tuberculosis, invasive fungal infections and bacterial and viral infections that resulted in hospitalizations and deaths. Pfizer previously announced that if a patients develops an infection while using Xeljanz, treatment should be interrupted until the infection is controlled.
As Xeljanz blood clot injuries emerged, the FDA required Pfizer to conduct post-marketing safety clinical trials to reassess dosing levels and compare the rate of blood clot, cardiovascular disease, cancer development and overall mortality rates to patients taking alternative tumor necrosis factor (TNF) inhibitors. This led to the latest results, which have not yet been finalized or fully analyzed, but suggest risks associated with Xeljanz may be more serious than Pfizer discloses on the drug label.
Since Xeljanz was first introduced into the market in 2012, roughly 1% of the population is anticipated to have used or currently be using the medication. The company’s multi-purpose drug has been steadily increasing in sales each year, reaching blockbuster status with sales in excess of $1 billion per year. However, as Pfizer attempts to preserve profits by delaying the introduction of generic equivalents, it also faces a number of potential Xeljanz lawsuits being pursued by former users who have suffered a pulmonary embolism, deep vein thrombosis (DVT), stroke, heart attack or cancer diagnosis.