The excitement surrounding a new drug is often cause for celebration for its developers, especially if it shows promise in early clinical trials.
But the new weight loss drug retatrutide has become a headache not only for the pharmaceutical company that makes it, Eli Lilly, but also for drug regulators in Britain and around the world.
This injection has not yet been approved for use in humans by any regulatory body. But the black market is flooded with counterfeits and illegal copies of retatrutide.
Experts told the BBC that this may be the first time that counterfeit versions of an experimental drug have become so widely available, while the original drug is still undergoing testing.
Vials of this medicine, which has become famous by the name 'Reta', are being sold in Britain in gyms, nail and beauty salons, hairdressers, social media and even by flower sellers on the street.
“The world has gone crazy,” says Seher Shahid, pharmacist and director of 24 HR Pharmacy.
"People are actually injecting an illegal drug and thinking it's safe."
“It has become so common that people are openly talking about their dealers, telling where they can get the best ones and posting places on social media.”
Within minutes of a cursory glance at my social media I could order a batch of a drug being sold under the name retatrutide – although there would be no evidence of what it was actually made of, what its effects were, or where it came from.
Enthusiasts who have been using it have been posting 'Reta' before and after photos on their TikTok feeds, saying it has calmed food noise, helped them lose weight and inches, and some say it has completely changed their lives.
The problem is that the safety and effectiveness of the original retatrutide is still under testing, despite positive results in recent clinical trials.
Only 50% of drugs that reach Phase III trials in the US ultimately receive Food and Drug Administration (FDA) approval, so there is no guarantee that retatrutide will come to market.
The main reasons for high failure rates are that drugs do not work as well in large, diverse human populations as they appear in smaller early trials, or they expose themselves to unexpected safety risks.
And the counterfeit versions currently available may not exactly match the original drug being developed in the safe confines of a laboratory.
Eli Lilly's website warns sternly, "No one should take any drug sold under the name retatrutide outside of a Lilly-sponsored clinical trial."
"Illegal retatrutide products may contain unknown ingredients, harmful contaminants, and impurities. They may contain too much or too little of the active ingredient, or may even be the wrong ingredient altogether."
Despite this, it seems that many people are willing to take this risk.
“Young and otherwise healthy patients are coming to hospital with nausea, vomiting, diarrhoea, and in some cases, kidney failure,” says endocrinologist Professor Donal O'Shea.
He says that some personal trainers are not only giving this medicine to their clients, but are also giving them injections.
“Patients have no idea how much they have taken, or what exactly they have been injected with.”
Tom Davis says he almost ended up in the hospital after overdosing on fake retatrutide. When his gym friends recommended it, he ordered it from a supplier in China.
“It was horrible,” says Tom, 20, from Brighton.
“There was a lot of pressure on my body, my stomach felt very bloated, as if someone had placed a 20 kg weight on my stomach.”
"I had really bad diarrhea and nausea for 72 hours. I thought, if this continues, I'll end up straight in the emergency ward."
Tom later realized that he had taken eight times the prescribed dose.
Dr. Nais Khattak, a research physician based in Chester, is screening patients for Eli Lilly's Phase III clinical trial. He says people taking the counterfeit versions are actually behaving like lab rats without any medical monitoring.
"People buying it online are taking a huge risk if they become doctors themselves," he warns.
Currently marketed obesity drugs – such as semaglutide (marketed as Ozempic and Vegovy), and tirazepatide (marketed as Mounjaro) – target only one or two hormone receptors. But if approved, Retatrutide will be the world's first weight loss drug that will work on three receptors, which is why it has been nicknamed 'Triple G'.
Lisa King has been taking counterfeit Retatrutide since July and at one point, while she was going to the gym and eating healthy, she was losing up to 3 pounds a week.
Eli Lilly has been developing retatrutide for almost 10 years. Now the company is trying to protect its product and stop illegal sales around the world.
"Any retatrutide available online is not approved, not verified and simply not worth the risk," a company spokesperson told the BBC.
Britain's Medicines and Healthcare products Regulatory Agency (MHRA) has seized "a number of products claiming to contain retatrutide" during raids over the past year.
Currently, there is still a long time for Retatrutide to be approved anywhere.
Eli Lilly plans to apply to the US FDA early next year. The review could take up to a year, so retatrutide will not be legally available in the US until the end of 2027.
