Public Health

Can a New Weight Loss Treatment Escape the Legal and Regulatory Thicket?

It’s Eli Lilly vs. RFK Jr. in a battle over the rules around Retatrutide.

Jen Basile | 9.10.2026 6:30 AM

Share on FacebookShare on XShare on RedditShare by emailPrint friendly versionCopy page URL Add Reason to Google

Media Contact & Reprint Requests

(Photo: Jonathan Alcorn/ZUMAPRESS/Newscom/Kateryna Borodina/Dreamstime)

On September 24, Eli Lilly and the Food and Drug Administration (FDA) will begin oral arguments before the 7th Circuit Court of Appeals in Eli Lilly and Company v. Robert F. Kennedy, Jr. Officially, the case is about a narrow technical question: Is Eli Lilly's experimental weight loss treatment retatrutide a biologic product or a conventional drug?

But it's actually about the legal and bureaucratic gymnastics Lilly is performing to protect its upcoming peptide from molecular copycats and how affordability will likely suffer if it succeeds.

Retatrutide is one of the most exciting new medicines to come to market in years. It's a metabolic blockbuster in waiting. In clinical trials, it produced an average weight loss of 28.3 percent in 80 weeks, roughly matching the most effective forms of bariatric surgery. Lilly plans to submit it to the FDA for approval in early 2027.

Peptides are all over the news, including the July start of Medicare's pilot program for weight loss GLP-1s and RFK Jr.'s efforts to move some experimental peptides off of the FDA's 503A Category 2 list of banned substances. Yet this new medicine has become entangled in a regulatory and legal mess involving FDA classification rules, the intricacies of administrative law, and competing claims about who gets to decide what it even means to be a drug.

Everyone loves to hate big pharma, but Lilly isn't really the villain of this tale. The system that is supposedly designed to promote safety, affordability, and availability of the latest medicines is making it harder to develop them, harder to bring them to market, and harder for patients to get them. 

How Did We Get Here?

Retatrutide is a GLP-1/GIP/Glucagon triple receptor agonist, the next generation of the hugely successful class of drugs known as GLP-1s, a group of medications that includes the peptides semaglutide and tirzepatide, such as Wegovy and Zepbound. Eli Lilly has spent the last decade developing retatrutide. But now Lilly has a problem.

Right now, patients can obtain GLP-1s through several channels. In addition to patent holders, compounding pharmacies and "research-use only" (RUO) providers are also selling the weight loss medications. These pathways are good news for customers anxious to try the new generation of weight loss drugs, who would otherwise be stymied by price or availability, but bad news for manufacturers.

FDA regulations allow compounding pharmacies to create customized medications for........

© Reason.com