For almost two years, Lilly has been warning consumers not to take knockoff versions of the shot that are being sold online and at wellness clinics and medical spas. It hasn’t been approved by regulators anywhere in the world.

Now, Lilly is upping the pressure. The drugmaker filed a handful of lawsuits against US businesses, many in Texas, that sell retatrutide products illegally. It’s also asking regulators to do more to rein in the illicit market. The lawsuits cite customer complaints and social media advertisements.

One business, Lilly said, offered a calculator to help people figure out what dosage of retatrutide they should be taking. That’s typically done by a licensed doctor.

Businesses that enable and facilitate the sales — including credit card companies, shipping firms and social media sites — also have a role to play in protecting consumers, Lilly said, calling it an “urgent public health crisis.”

Max Denning, an associate vice president at Lilly who oversees global patient safety for its cardiometabolic health division, said tracking knockoff retatrutide is like a game of “whack-a-mole.” The drugs are frequently made by unregulated foreign manufacturers, according to Lilly.

“It’s a huge problem, a global problem,” Denning said in an interview. “It’s not something we can tackle alone.”

Lilly shares fell 1% at 9:55 a.m. in New York on Wednesday. 

The US Food and Drug Administration has said it’s illegal for pharmacies to compound retatrutide. Since 2024, the FDA has sent warning letters to at least 16 companies claiming to sell it. As of Aug. 11, however, many were still offering knockoff versions, according to a Bloomberg analysis. 

In a statement, an FDA spokesperson urged consumers “not to use retatrutide unless they are part of a clinical trial.” The spokesperson added that “compounded drugs are not FDA approved, which means the agency does not review their safety, effectiveness or quality.”

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Behind the scenes, Lilly has been working for years to disrupt the global retatrutide trade. The company has referred more than 200 entities to the FDA, the US Department of Justice, state attorneys general, law enforcement and professional licensing boards. Lilly says it has reported more than 14,000 websites, advertisements, social media posts and product listings in over 100 countries, but some companies continue to amplify misleading content to vulnerable consumers.

Lilly and rival Novo Nordisk A/S have been fighting a similar battle against copycat versions of their bestselling weight-loss drugs Zepbound and Wegovy. But retatrutide has taken that fight to a new level. 

The hype about retatrutide has been building for years, ever since Lilly revealed results from a mid-stage study that suggested the drug might be more powerful than any weight-loss drug currently on the market. Since then, people all over the world have been clamoring to get their hands on black-market versions, buying them from overseas sellers who market them as “research-use only” to avoid scrutiny. On social media, the drug is called “reta” or “r3ta,” sometimes even “ratatouille,” as people increasingly find workarounds to avoid some of the restrictions that companies like TikTok have put in place on content related to weight loss.

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If approved by regulators, retatrutide is expected to generate more than $5.4 billion in annual sales for Lilly by 2030. But the black market could pose a major risk. Any safety concerns that emerge with knockoff versions could threaten the drug’s reputation, even though Lilly has been running its own large-scale clinical trial program on the medication. The company plans to seek approval from the FDA early next year. 

Lilly said there’s been some “encouraging” actions taken by federal and state authorities, including a large Customs and Border Protection seizure in Cincinnati last year. Federal prosecutors have also been targeting illegal sellers, and last month a judge sentenced the owner of a popular peptide company that sold retatrutide to nearly six years in prison.

Denning said Lilly is also engaging with law enforcement in the UK, Brazil, New Zealand, Saudi Arabia and Hong Kong. The company is urging regulators and law enforcement agencies to prioritize enforcement actions and “to coordinate across borders to dismantle the criminal networks” involved in selling retatrutide, he said.

(Updates with share move and FDA comments from the eighth paragraph.)