Eli Lilly has asked to join in opposing a lawsuit brought by compounding pharmacies against the U.S. Food and Drug Administration over the agency's decision that Lilly's blockbuster weight-loss and diabetes drugs are no longer in short supply.

After plugging billions into its manufacturing network to meet rampant demand for Mounjaro and Zepbound, Eli Lilly is looking to protect its investment by wading into a lawsuit that seeks to allow | After plugging $23 billion into its manufacturing network to meet rampant demand for Mounjaro and Zepbound,

It hasn’t been a smooth year for the two pharma giants, but events in the fourth quarter widened the gap between them.

The United States Food and Drug Administration says the shortage of Eli Lilly’s Zepbound and Mounjaro drugs has been resolved and that specialty pharmacies and online companies need to stop selling off-brand versions of the weight-loss drugs. The FDA has issued warnings against the off-brand versions, citing safety concerns.

In a recent head-to-head study involving Novo Nordisk 's Wegovy, Zepbound came out on top, resulting in average weight loss of about 20%, compared to more than 13% for the rival medicine. Lilly and Novo Nordisk both are leaders in this market today.

Eli Lilly (NYSE:LLY) is reportedly seeking to oppose a lawsuit filed by compounding pharmacies over the FDA's determination that weight-loss and diabetes drugs such as Lilly's (NYSE:LLY) tirzepatide are no longer in short supply.