, which compared the investigational agent to insulin glargine for treatment of type 2 diabetes. The study comprised 1,995 randomized patients with inadequately controlled type 2 diabetes and high cardiovascular disease risk.
Positive results for tirzepatide from, the fifth and final registration trial for the drug, as well as in the other four studies, tee up the agent for a planned approval submission to the Food and Drug Administration by the end of 2021.
SURPASS-4 differed from the four other pivotal trials not only in its comparator agent, but also by being the longest of the five and the only one that, by design, enrolled exclusively patients with either established cardiovascular disease or high risk for the disease.
The new results “provide initial support for glycemic control [by tirzepatide] being sustained for more than 1 year,” wrote, and associates in their in The Lancet.
Despite the trial’s primary endpoint of change in hemoglobin A1c after 52 weeks on treatment, the study continued for another year and had a median time on treatment of 85 weeks, with 7% of enrolled patients remaining on treatment for the maximum on-treatment follow-up of 104 weeks.
Potent glycemic control
The primary endpoint showed that treatment with tirzepatide produced an average incremental reduction in A1c of 0.99% among 328 patients treated with a 10 mg weekly subcutaneous dosage compared with the 1,000 patients who received insulin glargine (Basaglar, Lantus, Toujeo), and an average 1.14% incremental reduction in A1c among 338 patients on a 15-mg dosage once weekly, reported Dr. Del Prato, professor and chief of the section of diabetes at the University of Pisa (Italy).
This met the prespecified criteria for noninferiority of tirzepatide to insulin glargine for reduction of A1c, the study’s primary objective, and also met the study’s prespecified definition of superiority, both statistically significant results. The study also tested a weekly tirzepatide dosage of 5 mg that was significantly superior to insulin glargine for glycemic control.
“The magnitude of A1c reduction and the proportions of patients reaching glycemic targets appear to be larger than in similar studies in which GLP-1 [glucagon-like peptide–1] receptor agonists have been compared with glargine,” the investigators wrote in their report.
The A1c effect of tirzepatide seen across all five SURPASS trials “surpasses what we’ve seen with other [glycemia control] drugs, with the possible exception of insulin,” said, professor of clinical diabetes and metabolism at Uppsala (Sweden) University.
The results also showed several other clinically meaningful benefits from tirzepatide treatment. A composite outcome of reduction of A1c to less than 7% with no weight gain and no clinically significant documented symptomatic or severe hypoglycemia occurred in 74%-88% of patients in the three tirzepatide arms compared with 13% of patients treated with insulin glargine. After 52 weeks on treatment, body weight fell by an average of 8%, 11%, and 13% from baseline in the three tirzepatide treatment arms in a dose-dependent way, while weight rose by an average of 2% among those who received insulin glargine. Weight reduction of at least 10% occurred in 36%-66% of patients treated with tirzepatide, compared with 2% on treatment with insulin glargine.
SURPASS-4 was not run as a blinded study because of differences in administration of the comparator agents.