Tirzepatide, a novel “twincretin” agent, was superior to 1-mg semaglutide treatments for reducing both hemoglobin A1c levels and body weight in patients with type 2 diabetes in a pivotal, 40-week, head-to-head trial with nearly 1,900 randomized patients, one of four positive pivotal trial results reported for tirzepatide at the annual scientific sessions of the American Diabetes Association.
‘Twincretin’ meets primary endpoints in five pivotal diabetes trials
“Across all four studies we see a significant and clinically meaningful decrease in A1c, and robust weight loss. The results exceeded our expectations” for both these outcomes, said Laura Fernández Landó, MD, senior medical director for tirzepatide at Lilly, the company developing the agent, and a coauthor on the semaglutide comparison study as well as on other tirzepatide reports at the meeting.
“This opens up a new avenue for results in diabetes therapy,” Jens Juul Holst, MD, remarked in a press conference.
SURPASS-2 compared three different tirzepatide doses delivered once weekly by subcutaneous injection against a 1-mg weekly, subcutaneous dose of semaglutide (Ozempic) in 1,879 adults who had been diagnosed with type 2 diabetes for an average of almost 9 years. All patients were already on metformin treatment that had proved inadequate for controlling their hyperglycemia; enrolled patients had an average A1c of 8.28%. The trial’s primary endpoint was change from baseline in A1c levels after 40 weeks.
Significant differences at each dose level
Patients on each of the three tirzepatide doses – 5 mg, 10 mg, or 15 mg once weekly – showed dose-dependent reductions in A1c that, for each dose, were significantly better than the reduction achieved with semaglutide. The highest tirzepatide dose reduced A1c levels by an average of 0.45% more than what semaglutide achieved, reported first author Juan P. Frias, MD; Dr. Landó; and their coauthors.
One key secondary endpoint was weight reduction, and each of the three tirzepatide doses again produced significant incremental loss beyond what semaglutide produced. The 5-mg weekly dose of tirzepatide produced an average 1.9-kg additional weight loss, compared with semaglutide, while the 15-mg dose resulted in an average 5.5-kg loss beyond what semaglutide achieved and a total average weight loss of 11.2 kg from baseline.
The study’s additional key secondary endpoints, the percentages of patients reaching an A1c of less than 7%, and less than 5.7%, also showed significantly better numbers with tirzepatide. The highest tirzepatide dose pushed 86% of patients below the 7% mark, compared with 79% on semaglutide, and the top tirzepatide dose resulted in 46% of patients getting their A1c below 5.7%, compared with 19% of patients on semaglutide.
Dr. Jens Juul Holst
The findings are “stunning, I must stay, and those results included that up to half of the patients treated with high doses of tirzepatide may reach A1c levels of less than 5.7%, which is really, really unheard of,” said Dr. Holst, professor of endocrinology and metabolism at the University of Copenhagen. Along with the “weight losses at the same time of up to 12% in that patient group, we are seeing some completely unexpected and really shocking and wonderful new advances in the therapy,” added Dr. Holst.
The safety profile of tirzepatide was roughly similar to semaglutide’s and to that other agents in the glucagonlike peptide-1 receptor agonist (GLP-1 RA) class. Concurrently with the report at the meeting, the results also appeared in an article published online in the New England Journal of Medicine.
An ‘impressive’ weight loss effect
Weight loss on tirzepatide was “impressive,” commented Katherine R. Tuttle, MD, a nephrologist affiliated with the University of Washington and executive director for research at Providence Health Care in Spokane, Wash. Another striking feature of tirzepatide’s weight-loss effect was that it did not plateau during the 40 weeks of the study, Dr. Tuttle noted in an accompanying editorial that accompanied the published report, a finding that suggests the potential for additional weight loss from continued treatment .
“The weight loss is remarkable,” commented Rodolfo J. Galindo, MD, an endocrinologist at Emory University, Atlanta. While incremental reduction of A1c on the order of less than 0.5% is helpful, incremental weight loss of more than 10 lbs on tirzepatide, compared with semaglutide “will likely be a tie-breaker” for many clinicians and patients to favor tirzepatide over semaglutide or another GLP-1 RA agent, he said in an interview. Dr. Galindo also cited other important factors that he predicted will drive decisions on using tirzepatide or a GLP-1 RA once tirzepatide reaches the U.S. market: relative cost, access, and tolerability.
The important issue of dose
But the edge that tirzepatide showed over semaglutide for weight loss did not occur on a completely level playing field. The 1 mg/week dose of semaglutide used as the comparator in SURPASS-2 was the maximum dose available at the time the study began, but in June 2021 the Food and Drug Administration approved a 2.4 mg/week dose (Wegovy) labeled specifically for weight loss. Dr. Tuttle cited the limitation this introduces in her editorial.
“The dose issue is important,” she wrote. The doses of tirzepatide and semaglutide compared in SURPASS-2 “were not comparable in terms of weight outcomes” given that prior evidence showed that the 2.4 mg/week semaglutide dose is more appropriate for weight loss.
Dr. Katherine R. Tuttle
Dr. Tuttle also cited other factors to consider when assessing tirzepatide compared with agents in the GLP-1 RA class.
Several GLP-1 RA agents, including semaglutide, have proven efficacy for reducing rates of atherosclerotic cardiovascular events and albuminuria, and they also slow decline in kidney function and progression of diabetic kidney disease. No details on the renal effects of tirzepatide appeared in the SURPASS-2 report. A press release from Lilly in May 2021 briefly mentioned results from a meta-analysis of several clinical studies of tirzepatide that showed a nonsignificant effect from tirzepatide on the incidence of major cardiovascular adverse events (death from cardiovascular or undetermined causes, MI, stroke, and hospitalization for unstable angina) relative to comparator groups. Results from a dedicated cardiovascular outcomes trial in high-risk patients treated with tirzepatide, SURPASS-CVOT, are not expected until 2024.
A further limitation of SURPASS-2 was the demographics of the enrolled population, which had a low (0.4%) enrollment rate of Black patients, and a high proportion (70%) of Hispanic patients, Dr. Tuttle observed.
Low rates of hypoglycemia
Another notable finding from SURPASS-2 was the low incidence of clinically significant hypoglycemic events (blood glucose levels less than 54 mg/dL), which occurred in 0.2%-1.7% of patients on tirzepatide, depending on their dose, and in 0.4% of patients on semaglutide. Two patients in the tirzepatide cohort had severe hypoglycemia.
These numbers are reassuring, said Dr. Galindo, and reflect the safety of tirzepatide’s dual, incretin-like mechanisms of action that make it a “twincretin.” The molecule acts as both a GLP-1 RA, and as glucose-dependent insulinotropic polypeptide, an incretin that stimulates insulin release when blood sugar is high but also increases glucagon levels when blood sugar levels are normal or low. This dual action may help explain the apparent increased potency tirzepatide showed for both A1c reduction and weight loss, compared with semaglutide, which acts only as a GLP-1 RA.
Some experts have cited the uncertainty introduced by the open-label design of SURPASS-2, a decision necessitated by the distinctly different delivery devices used for tirzepatide and semaglutide, explained Dr. Landó. But she highlighted that double blinding applied to the three different tirzepatide dosages tested in the trial. Dr. Landó said that Lilly plans to seek FDA approval for all three tested tirzepatide doses to give clinicians and patients flexibility in applying the treatment.
SURPASS-2 used a prolonged dose-escalation protocol designed to minimize gastrointestinal adverse effects that started patients on a 2.5 mg weekly dose that then increased by 2.5 mg increments every 4 weeks until patients reached their assigned target dose. This meant that patients did not begin receiving the 15-mg/week dose until halfway through the trial.
Several more tirzepatide trials
Reports from two other pivotal trials for tirzepatide also appeared as posters at the meeting. SURPASS-5 compared tirzepatide with placebo in 475 patients inadequately controlled with titrated insulin glargine (Lantus). SURPASS-3 randomized 1,444 patients to tirzepatide or titrated insulin degludec (Tresiba). In both studies treatment with tirzepatide led to significantly better reductions in A1c and in weight loss than the comparator treatments. Results from a third pivotal trial, SURPASS-1 which compared tirzepatide against placebo in 478 treatment-naive patients, will come in a report scheduled for the second day of the meeting.
The results from all the recent tirzepatide trials show a consistent benefit across the continuum of patients with type 2 diabetes regardless of whether it’s recent onset or well-established disease, said Dr. Landó.
The SURPASS studies were sponsored by Lilly, the company developing tirzepatide, and the reports include several authors who are Lilly employees. Dr. Landó is a Lilly employee and stockholder. Dr. Tuttle has been a consultant to Lilly and to Novo Nordisk, the company that markets semaglutide, as well as to AstraZeneca, Bayer, Boehringer Ingelheim, Gilead, and Janssen. She has also received travel expenses from Kyokawa Hakko Kirin, and research funding from Bayer, Goldfinch Bio, and Lilly. Dr. Galindo has been a consultant to Lilly and to Novo Nordisk, as well as to Abbott Diabetes Care, Sanofi, Valeritas, and Weight Watchers, and his institution has received grant support on his behalf from Lilly, Novo Nordisk and Dexcom. Dr. Holst had no disclosures.