Study: Real-world results of GLP-1 drugs don't match trials

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Real-world results for blockbuster weight-loss meds like Ozempic, Wegovy and Zepbound aren't as impressive as those promised by the drugs' clinical trials, a new study says. Photo by Adobe Stock/HealthDay News
Real-world results for blockbuster weight-loss meds like Ozempic, Wegovy and Zepbound aren't as impressive as those promised by the drugs' clinical trials, a new study says.
People taking such GLP-1 drugs lost just under 9% of their body weight on average after a year, researchers reported Tuesday in the journal Obesity.
That's far less than the 15% to 21% body weight reduction promised by the clinical trials that led to the approval of Wegovy (semaglutide) and Zepbound (tirzepatide) for weight loss, researchers said.
"Patients treated for obesity with semaglutide or trizepatide lost less weight on average in a regular clinical setting compared to what is observed in randomized clinical trial," lead investigator Hamlet Gasoyan said in a news release. He is a researcher at the Cleveland Clinic Center for Value-Based Care Research.
People taking the drugs in real-world settings appear to be more likely to quit taking the meds, researchers said. They also might be prescribed lower dosages in clinical practice than were used in the drug trials.
Glucagon-like peptide-1 (GLP-1) drugs mimic the GLP-1 hormone, which helps control insulin and blood sugar levels, decreases appetite and slows digestion of food.
For this study, researchers tracked nearly 7,900 patients being treated by the Cleveland Clinic for severe obesity, of whom about 6,100 were prescribed semaglutide and the rest tirzepatide.
Average body weight loss after a year was nearly 9% for the whole group, results show.
But weight loss varied based on when a person stopped taking the drugs, researchers found.
Average weight loss was under 4% for those who stopped treatment early, versus nearly 7% or those who stopped later on, the study says. Those who stayed on their medications lost an average 12% body weight.
Results also show that more than 4 in 5 (81%) of patients were prescribed a low maintenance dose of their GLP-1 drug, and that made a difference as well.
People who stayed on their meds and received high doses lost nearly 14% of their body weight with semaglutide and 18% with tirzepatide.
"Our findings about the real-world use patterns of these medications and associated clinical outcomes could inform the decisions of health care providers and their patients on the role of treatment discontinuation and maintenance dosage in achieving clinically meaningful weight reductions," Gasoyan said.
Overall, patients had higher odds of losing 10% or more of their body weight after a year if they remained on their meds, were prescribed a high dosage, were taking tirzepatide rather than semaglutide, and were female, results show.
The cost of the drugs and problems were insurance were a common reason for patients stopping GLP-1 treatment, along with side effects and medication shortages, researchers said.
Staying on the GLP-1 meds particularly helped the nearly 17% of patients who had prediabetes, a condition in which elevated blood sugar levels increase a person's risk of developing Type 2 diabetes.
About 68% of those who stuck with their treatment wound up with normal blood sugar levels, compared with 41% who stopped taking the drugs later in the study and 33% who stopped earlier.
"Type 2 diabetes is one of the most common complications of obesity, so diabetes prevention is very important," Gasoyan said. "This study highlights that treatment discontinuation, especially early, negatively affects both weight and glycemic control outcomes."
A follow-up study is in the works to better track why patients stop taking their GLP-1 drugs, researchers said.
More information
Harvard Medical School has more on GLP-1 drugs.
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