More than half of patients taking the two highest doses of tirzepatide as a once-weekly injection lost at least 20% of their body weight in the first phase 3 trial to examine this agent in patients with obesity, but without diabetes, according to preliminary top-line results from the SURMOUNT-1 trial announced by Lilly.
The full results will be reported at an upcoming medical conference and published at a later date, Lilly added.
There was much excitement in response to the news, but others have urged caution and noted that, even if tirzepatide is eventually approved for obesity, one of the major barriers to use in the United States will be insurance coverage.
"Wow (and a double Wow!) 52lb weight loss (22.5%) at highest dose of tirzepatide," tweeted Sek Kathiresan, MD, a cardiologist who is cofounder of Verve Therapeutics and on leave from Harvard (@skathire).
"Thus far the challenge with GLP-1s [agonists] for management of obesity is that insurance usually isn't covering them. This makes them unaffordable for most people," replied James Marroquin, MD, of the University of Texas at Austin. (@Jamesmarroquin).
Yoni Freedhoff, MD, University of Ottawa, Ontario, Canada, who writes a column for Medscape on obesity, said if tirzepatide pans out, along with other similar agents already on the market for this indication, "the next few decades should see the pharmaceutical management of obesity rival its surgical management."
Would Compete With "Gamechanger" Wegovy?
Tirzepatide has been dubbed a "twincretin" because it works as an agonist of the glucagon-like peptide-1 (GLP-1) receptor but also of the glucose-dependent insulinotropic polypeptide (GIP) receptor. It has been much hyped based on the results of the series of SURPASS clinical trials, which has formed the basis of the application for type 2 diabetes approval, about which the US Food and Drug Administration is expected to make a decision soon.
Several GLP-1 agonists are on the market for both type 2 diabetes and for obesity indications separately, including semaglutide (marketed as Wegovy for obesity, also a once-weekly injection) and liraglutide (Saxenda for obesity, a daily injection), both Novo Nordisk agents.
Wegovy was approved for weight loss in the United States last year, with doctors telling Medscape Medical News then that a third of patients who take the drug are likely to lose 20% or more of their starting weight, an outcome that approaches reductions seen with bariatric surgery.
Freedhoff said he'd like to see "reimbursement by insurers who will see these drugs serving as important ancillary treatments for the myriad of weight responsive conditions they're already covering."
SURMOUNT-1 DATA: "Impressive Body Weight" Reductions
The new tirzepatide data come from the multicenter, randomized, double-blind, placebo-controlled SURMOUNT-1 trial, which included 2539 participants from the United States, Argentina, Brazil, China, India, Japan Mexico, Russia, and Taiwan. They had obesity or overweight plus at least one comorbidity but not diabetes. They were randomized to 5-mg, 10-mg, or 15-mg once-weekly tirzepatide or placebo injections for 18 months (72 weeks).
Efficacy was analyzed in two ways. Prior to factoring in drug discontinuation, participants taking tirzepatide experienced weight loss of 16.0% (35 lbs/16 kg) with 5 mg, 21.4% (49 lbs/22 kg) with 10 mg, and 22.5% (52 lbs/24 kg) on 15 mg. In contrast, the placebo group lost just 2.4% of body weight (5 lb/2 kg).
But treatment discontinuation rates due to adverse events were 4.3%, 7.1%, 6.2%, and 2.6%, for tirzepatide 5 mg, 10 mg, 15 mg, and placebo, respectively. Overall treatment discontinuation rates were 14.3%, 16.4%, 15.1%, and 26.4%, respectively.
When efficacy was assessed regardless of treatment discontinuation, average body weight reductions were 15.0%, 19.5%, 20.9%, and 3.1% for tirzepatide 5 mg, 10 mg, 15 mg, and placebo, respectively.
More than half of patients taking tirzepatide 10 mg and 15 mg (55% and 63%, respectively) lost at least 20% of their body weight, compared with just 1.3% taking placebo.
Overall safety and tolerability were similar to those of other GLP-1 agonists, with adverse events being gastrointestinal in nature and increasing with higher doses. Nausea affected 24.6%, 33.3%, and 31.0% of the tirzepatide 5-mg, 10-mg, and 15-mg dose groups, respectively, and vomiting was experienced by 8.3%, 10.7%, and 12.2% of patients, respectively. Diarrhea and constipation were also reported more often with the drug than placebo.
"Tirzepatide delivered impressive body weight reductions in SURMOUNT-1, which could represent an important step forward for helping the patient and physician partnership treat this complex disease," said study investigator Louis J. Aronne, MD, director of the Comprehensive Weight Control Center and the Sanford I. Weill Professor of Metabolic Research at Weill Cornell Medicine, New York City, in a press release.
Further studies are ongoing for tirzepatide as a potential treatment for obesity or overweight, according to the Lilly statement. SURMOUNT is a phase 3 global clinical development program for tirzepatide that began in late 2019 with over 5000 people with obesity or overweight across six clinical trials. Results from SURMOUNT-2, SURMOUNT-3, and SURMOUNT-4 are expected in 2023.
Tirzepatide is also being studied as a potential treatment for nonalcoholic fatty liver disease and heart failure with preserved ejection fraction. Studies of tirzepatide in obstructive sleep apnea and of morbidity/mortality in obesity are also planned.
Aronne is cofounder, chief scientific advisor, and a member of the board of directors for Intellihealth. He is also a paid scientific advisory board member for Eli Lilly. Freedhoff has served or is serving as a director, officer, partner, employee, advisor, consultant, or trustee for the Bariatric Medical Institute and Constant Health and has received a research grant from Novo Nordisk.
Miriam E. Tucker is a freelance journalist based in the Washington, DC, area. She is a regular contributor to Medscape, with other work appearing in The Washington Post, NPR's Shots blog, and Diabetes Forecast magazine. She is on Twitter: @MiriamETucker.