NEW ORLEANS – Treatment of people with obesity but no diabetes with the dual–incretin agonist tirzepatide safely produced “unprecedented” levels of weight loss in the vast majority of patients in SURMOUNT-1, a placebo-controlled trial with more than 2,500 people with obesity or overweight plus at least one weight-related complication.
Although the pivotal trial did not directly compare weekly subcutaneous injection with the twincretin tirzepatide (at 5 mg, 10 mg, or 15 mg) with either bariatric surgery or what has been the reigning champ of weight-loss agents, a 2.4-mg/week injection of semaglutide (Wegovy), the new findings are impressive because they eclipsed semaglutide’s past performance in at least three important ways, said Ania M. Jastreboff, MD, PhD, SURMOUNT-1’s lead investigator, at the annual scientific sessions of the American Diabetes Association.
Dr. Ania M. Jastreboff
First, the highest-tested dosage of tirzepatide, 15 mg/week, for 72 weeks, produced a 5% or greater loss in baseline weight in 91%-96% of patients, an effect “not previously seen” in any prior phase 3 trial of a weight-loss agent, noted Dr. Jastreboff, an endocrinologist and director of Weight Management & Obesity Prevention at Yale University in New Haven, Conn.
Second, the average level of weight loss among the 630 people who received 15 mg/week was 22.5% in the on-treatment analysis, and 20.9% in the intention-to-treat analysis, again a magnitude of effect never before seen with any other medical intervention.
And in an exploratory analysis, 40% of people who received the highest-tested tirzepatide dose of 15 mg/week had at least a 25% loss in baseline weight in the on-treatment analysis, another example of unprecedented weight-loss achievement, said Dr. Jastreboff.
Looking at the data another way, the average baseline weight of those in the trial was 104 kg (230 lb) at the start, and the average weight loss was between 35 and 52 lbs by 72 weeks on treatment, Dr. Jastreboff said in a press conference.
She noted, however, that not everyone will respond to tirzepatide, “but if you do respond to this medicine, you will feel full earlier, you won’t want to go back for seconds, and you may eat smaller amounts more often.”
Such weight-loss agents will need to be taken chronically, in the same way that medications are for hypertension or dyslipidemia, Dr. Jastreboff stressed. “If you stop the antiobesity medication then the body fat mass set point will go back up so this necessitates long-term treatment.”
A new era: Weight loss ‘in the range of bariatric surgery’
Tirzepatide, developed by Lilly, has recently been approved in the United States for the treatment of type 2 diabetes, under the brand name Mounjaro.
SURMOUNT-1 was designed to examine the effect of the agent in overweight/obesity, and the company will be filing for the additional indication of weight loss in the future. Top-line results of SURMOUNT-1 generated much excitement when Lilly reported them back in April, including a story in The New York Times.
Semaglutide, a Novo Nordisk drug, is approved in the United States for type 2 diabetes (as Ozempic at doses of either 1 mg or 2 mg per week) and also for weight loss, as Wegovy, at the higher dose of 2.4 mg per week. When Wegovy was given the green light by the Food and Drug Administration a year ago, it too was hailed as a “game changer” for obesity.
The weight-loss results seen in SURMOUNT-1 “put tirzepatide squarely in the range of weight loss achieved with bariatric surgery,” concluded Louis J. Aronne, MD, a coinvestigator on the trial, professor at Weill-Cornell Medicine in New York, and director of the Center for Weight Management and Metabolic Clinical Research of Weill-Cornell.
Dr. Lee M. Kaplan
The results are “amazing,” and propel the weight-loss field into “a new era of obesity treatment,” commented Lee M. Kaplan, MD, who was not involved in the study and served as designated discussant for the trial.
Despite the lack of direct comparison, the findings indicate that “tirzepatide causes more weight loss than semaglutide,” and it provides “an opportunity to meet or exceed” the weight-loss effects of bariatric surgery, added Dr. Kaplan, director of the Obesity, Metabolism and Nutrition Institute at Massachusetts General Hospital in Boston.
Simultaneously with Dr. Jastreboff’s report at the meeting, the results were published online in The New England Journal of Medicine.
An accompanying editorial agrees with Dr. Kaplan: “It is remarkable that the magnitude of weight loss with tirzepatide was similar to that with gastric bypass, which raises the potential for alternative medical approaches to the treatment of obesity.”
“The tides are shifting, and there are now more options for people with obesity to lose weight,” write Clifford J. Rosen, MD, of Tufts University, Boston, and Julie R. Ingelfinger, MD, of Harvard University and Massachusetts General Hospital, Boston.