Eli Lilly sues six companies in the USA for illegal sale of retatrutide, a molecule still under research

According to Lilly, the actions target compounding pharmacies, beauty clinics, medical spas and online sellers who sell the product claiming that it is intended "for research use only" when, in practice, it would be sold for human consumption.

Unlike semaglutide and tirzepatide, which act on one or two hormone receptors, retatrutide is a triple agonist. It activates receptors for the hormones GLP-1, GIP and glucagon, involved in the regulation of hunger, satiety, insulin production and energy expenditure.

No regulatory body in the world has yet approved medicines with retatrutide. Eli Lilly plans to submit a biologics license application for retread to the FDA (US Anvisa) in the first quarter of 2027.

"Retatrutide is being studied rigorously as part of a broad clinical trial development program," said David Hyman, Lilly's chief medical officer.

"We take seriously the responsibility of evaluating the safety and effectiveness of our investigational medicines. What is being sold on the underground market is not a medicine, it is something completely unverified, unapproved and not worth the risk."

The company says it has reported more than 200 people and entities to the FDA, the US Department of Justice, state prosecutors, law enforcement authorities and professional boards. It also says it has notified digital platforms about more than 14 thousand websites, advertisements and publications that would sell the product illegally in more than one hundred countries.

In the note, Lilly also reinforced the call for digital platforms, payment companies, transport companies and authorities to act against this market.

Interest in retatrutide grew as preliminary efficacy data suggested greater weight loss than already approved drugs. Two phase 3 studies presented by Lilly in July expanded the data on retatrutide.

The TRIUMPH-3 study evaluated 1,949 adults with severe obesity and established cardiovascular disease, with or without type 2 diabetes.

After one year and eight months, participants treated with retatrutide lost, on average, 23.9 kg, equivalent to 21.6% of body weight, at the 9 mg dose. At the 12 mg dose, the loss was 25.3 kg (22.6%). The placebo group showed an average reduction of 3.5 kg (3.2%).

The TRIUMPH-2 study included 1,152 adults with obesity or overweight and type 2 diabetes, a population with greater difficulty losing weight. At the 4 mg dose, participants lost, on average, 13.5 kg, equivalent to 12.7% of their body weight. With 9 mg, the average loss was 20.6 kg (19.1%). The 12 mg dose led to an average reduction of 22.5 kg, corresponding to 20.8% of the initial weight. In the placebo group, the loss was 4.2 kg (4%).

Although the drug is experimental and therefore does not officially exist on the market, seizures of weight-loss pens advertised as retatrutida have become common. The cases occur on the Brazilian side of the border with Paraguay.

Packages seized in Foz do Iguaçu and seen by Folha de S.Paulo at the Federal Revenue headquarters indicate Germany or even Paraguay as the countries of origin of the substance sold as retatruda. Inspectors state, however, that the actual place of production is uncertain.

Lilly do Brasil, in a statement to Folha de S.Paulo, states that retatrutide is legally available only to participants in clinical trials.

"Anything sold to consumers outside of these tests is illegal, with no way to verify its safety, purity or dosage. Taking unregulated substances poses serious health risks, and Lilly continues to work with law enforcement and regulatory authorities to combat black market drugs," says the pharmaceutical company.

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