Diabetes drug Mounjaro helped people lose 16% of weight, study finds

In a second large study, the drug Mounjaro, now used to treat diabetes, has shown its effectiveness at helping people lose weight.

The drug is not yet approved for weight loss, but likely will be later this year, now that two trials have found it effective with similar side effects as other weight loss medications.

The study, released by drug-maker Eli Lilly on Thursday, showed participants with diabetes lost nearly 16% of their weight over the 18-month trial. The company had already shown that the same drug, generically called tirzepatide, could help people with obesity but not diabetes lose more than 20% of their body weight.

It is generally harder for people with diabetes to lose weight and this is the first drug trial to show such significant weight loss for people with the disease, according to Lilly associate vice president Dr. Nadia Nazir Ahmad.

So far, data on the drug has only been released via a company news release. Ahmad said Lilly plans to release full results at the American Diabetes Association's annual meeting in San Diego in June and submit them to a peer-reviewed journal.

More: Experts worry the 'magic' in new weight loss medications carries a dark side

What is tirzepatide and how does it compare to Ozempic and Wegovy?

Tirzepatide, sold under the brand name Mounjaro, is approved for the treatment of diabetes.

It is believed to act on obesity in two ways, Ahmad said, by reducing appetite and affecting how the body burns fat.

Semaglutide, the generic name for the drug in both Ozempic and Wegovy, acts only on the first of those and thus appears to be slightly less effective at promoting weight loss, though they have never been compared in a head-to-head study. Lilly is currently in the planning stages for one, Ahmad said

Both semaglutide and tirzepatide are delivered by weekly injection.

Ozempic, Wegovy, Mounjaro: How these medications promote weight loss

What did the new trial show?

The new trial included 938 adults, one-third of whom received a 10-mg dose of tirzepatide, one-third received a 15-milligram dose, and one-third a placebo.

Those on the lower dose lost about 13% of their body weight, or about 30 pounds. That compares to nearly 16% weight loss of those on the higher dose, or about 34 pounds, and 3% or 7 pounds among those getting the placebo.

Less than 3% of the placebo group lost more than 15% of their body weight, compared to 40% of the low-dose group and 48% of the high-dose group.

A measure of diabetes severity, A1C also fell in people taking the drug.

Lilly has not said what dose it will request for approval from the Food and Drug Administration for weight loss.

Mounjaro is meant to be ramped up from a low, introductory dose of 2.5 milligrams to as much as 15 milligrams per weekly dose. The highest dose costs about $1,000 per month. Wegovy, which is a higher dose of the same drug as Ozempic, retails for about $1,300 a month.

Insurance, including the government's Medicare and Medicaid, typically covers the cost of medications for diabetes but not for weight loss.

More: Anti-obesity medications are set to skyrocket this year. But how will we afford them?

What happens if you stop taking Mounjaro?

These weight-loss medications are intended to be taken monthly for life.

Lilly's Ahmad noted that no one would think they could stop taking their blood pressure medication once their numbers reached a healthy level.

More: Obesity was long considered a personal failing. Science shows it's not.

Studies have shown that people tend to regain at least some of the weight once stopping medication. In the new trial, called SURMOUNT-2, Lilly followed patients for four weeks after stopping tirzepatide and found they began to regain.

The company is running another randomized study to look at what happens longer term after people stop the drug.

Side effects of Mounjaro

Tirzepatide and semaglutide have similar side effects. In the new trial, about 20% of people at both drug doses suffered nausea and diarrhea, 12% endured vomiting and 8% had constipation. In the placebo group, 6% had nausea, 9% diarrhea, 3% vomiting and 4% constipation.

Nearly 4% of those receiving placebo dropped out of the trial because of side effects, compared to the same percentage of people on the lower dose and 7% on the higher dose. Overall, a higher percentage of people receiving the placebo dropped out of the trial than those receiving the drug.

Lifestyle changes and tirzepatide

Lifestyle changes remain important while on tirzepatide, Ahmad said, but differ slightly from the typical recommendations.

When appetite is suppressed and the body is losing weight, she said, it's particularly important to eat a healthy diet and stay hydrated.

"Lifestyle is important with medications that treat chronic diseases," she said.

Contact Karen Weintraub at kweintraub@usatoday.com.

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This article originally appeared on USA TODAY: Mounjaro, tirzepatide found effective for weight loss, Eli Lily says