Eli Lilly said Wednesday it is suing six companies selling versions of its experimental weight-loss drug retatrutide, calling it the beginning of a concerted effort to crack down on a vast illicit market.

That market has boomed even though retatrutide is still being studied in clinical trials and hasn’t been approved by the Food and Drug Administration as safe and effective. Federal law prohibits the commercial sale of unapproved drugs, but many telehealth firms, clinics and peptide vendors online have decided to offer the next-generation drug anyway, as promising results from Eli Lilly’s trials have fueled a craze for it on social media.

“This is a global problem and it’s an enormous one,” Max Denning, an associate vice president at Eli Lilly, said in an interview, calling on regulators, social media companies, payment processors and others to help stem illicit sales of retatrutide. “Six lawsuits is not going to be the solution to everything, but it is a start,” he said.

The lawsuits Eli Lilly announced target a variety of companies that market retawhich Denning said is being supplied by “overseas manufacturers.” Four of the firms targeted by the drugmaker advertise the product “for research use” without a prescription: Astra Peptides, Legendary Peptides, Texas Peptides and Lone Star Peptide. Eli Lilly is also suing Aesthetic Envy, a California med spa that promotes retatrutide, and Striker Pharmacy, which has made a version of the experimental drug. Striker is one of several compounding pharmacies that have made imitation retatrutide identified by CBS News in a June investigation.

The companies didn’t respond to requests for comment Wednesday. Lone Star Peptide, Texas Peptides and Aesthetic Envy all took down their webpages advertising retatrutide.

Eli Lilly is running late-stage clinical trials to study retatrutide as a treatment for obesity and type 2 diabetes, and results so far have shown that it could be more effective than the most potent weight-loss drugs that have been approved by the FDA. The drugmaker said last month that it plans to seek regulatory approval for the drug in early 2027.

In its lawsuits, Eli Lilly alleges that companies claiming to sell retatrutide are endangering consumers with substances that haven’t been vetted by regulators and are more likely to contain contaminants. Such products also threaten Eli Lilly, the company says.

“Consumers are switching from Lilly’s FDA-approved medicines to illegal retatrutide products, citing purported lower costs and perceived superior efficacy,” the drugmaker states in its lawsuit against Striker Pharmacy. And if consumers experience bad reactions from such products, they will associate them with Eli Lilly’s drug, the company claims, “poisoning the well for the future of retatrutide medicines.”

Striker doesn’t publicly disclose retatrutide as a product, but Aesthetic Envy advertises the drug on its website, calling it a “cutting edge therapy” that “outperforms today’s leading medications.” 

“Aesthetic Envy fails to disclose that its retatrutide product has not been approved by the FDA or any other regulator in the world,” Eli Lilly states in its lawsuit.

The drugmaker further alleges that companies marketing retatrutide “for research use only” are actually tailored to consumers who want to inject themselves with the product. 

Wall Street analysts expect retatrutide to be a blockbuster, but have voiced concern about the illicit market. Asked last week by a financial analyst if the company had a strategy “to protect against whatever it is that’s apparently available today,” an Eli Lilly executive shrugged it off.

“I think people are eagerly awaiting authentic retatrutide to be available in the market,” said Kenneth Custer, an executive vice president, according to a transcript compiled by S&P Global Market Intelligence.

While Eli Lilly is hoping that regulators and law enforcement will take more action against companies claiming to sell retatrutide, some are increasingly doing so in the open, with apparently few if any consequences.

CBS News reported last month that convenience stores were advertising and selling vials of research-grade retatrutide. As recently as Aug. 8, two bodegas in Brooklyn still displayed posters advertising it along with other peptides. A cashier at one of them, a store called Mr. Green, said they were sold out of retatrutide.