'GLP-3s' explained as clinical trials show they are more effective than current weight loss jabs

'GLP-3s' could be the future of weight loss, some believe.

You'll have likely heard of GLP-1 agonists, which are a type of medication that blocks the action of Glucagon-Like Peptide-1 (a hormone that normally promotes insulin release and reduces appetite) and therefore helps people lose weight. Some of these drugs are also beneficial for people with diabetes.

Just as everyone is seemingly jumping on the GLP-1 bandwagon, there appears to be another drug that's been thrown into the mix that could prove more affective.

Back in December Eli Lilly, the maker of Mounjaro and Zepbound, announced a new 'triple agonist' called retatrutide that's earned itself the unofficial name of 'GLP-3'.

A trial conducted by the pharmaceutical company found that participants with obesity and knee osteoarthritis taking retatrutide 12 mg lost an average of 28.7 percent of their body weight at 68 weeks, per a press release.

A diagram demonstrating how GLP-1 functions (Getty Stock Image)

What is retatrutide?

According to Eli Lilly, this drug is an investigational once-weekly triple hormone receptor agonist.

"Retatrutide is a single molecule that activates the body's receptors for glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide-1 (GLP-1), and glucagon," the company says.

In comparison, the likes of semaglutide work by only mimicking GLP-1 only. Then there's tirzepatide that mimics both GLP-1 and GIP.

The key difference with retatrutide is that is mimics glucagon as well. This helps the body burn stored fat for fuel and reduces body weight, says The Independent.

Many Americans have tried some type of GLP-1 drug (Getty Stock Image)

The clinical trails

In one particular trial, called the TRIUMPH-4 clinical trial, participants were obese or were overweight, did not have diabetes, and were suffering with osteoarthritis (OA) of the knee. The medication was adjunct to a healthy diet and physical activity.

The purpose of the study was to 'evaluate the safety and efficacy of retatrutide once-weekly' with these factors in mind.

After 68 weeks it was found that people experienced 'significant weight loss and improvements in pain and physical function at 68 weeks using both the efficacy and treatment-regimen estimands'.

Participants lowered their weight by an average of 28.7 percent (just over 72lbs) and reduced pain by up to an average of 4.5 points, using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain score.

Eli Lilly appears to be optimistic about the benefits of retatrutide (Getty Stock Image)

Commenting on the study, Kenneth Custer, Ph.D., executive vice president and president, Lilly Cardiometabolic Health, said: "We are encouraged by the results of TRIUMPH-4, which highlight the powerful effect of retatrutide, a first-in-class triple agonist, on body weight, pain and physical function.

"With seven additional Phase 3 readouts expected in 2026, we believe retatrutide could become an important option for patients with significant weight loss needs and certain complications, including knee osteoarthritis."

When will it be available?

While Eli Lilly's triple agonist is yet to be licensed, its main competitor Novo Nordisk (the maker of Ozempic) announced back in March 2025 that it had reached a licensing agreement with Hong Kong-based pharmaceutical lab The United Laboratories.

Retatrutide wasn't named specifically but they spoke of a 'a triple agonist of the receptors for GLP-1, GIP, and glucagon'. The drug referenced in the press release was something called UBT251.

When people can expect the new 'GLP-3' medication to be available was not disclosed.