Lowering of blood pressure plateaus
Changes in BP over time during the 72 weeks on treatment, data first presented in the original report, showed that average systolic pressure in the people who received tirzepatide fell sharply during the first 24 weeks on treatment, and then leveled out with little further change over time. Furthermore, all three tirzepatide doses produced roughly similar systolic BP reductions. Changes in diastolic pressure over time showed a mostly similar pattern of reduction, although a modest ongoing decrease in average diastolic pressure continued beyond 24 weeks.
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Dr. Naveed Sattar
This pattern of a plateau in BP reduction has been seen before in studies using other treatments to produce weight loss, including bariatric surgery, said Naveed Sattar, MBChB, PhD, professor of metabolic medicine at the University of Glasgow, who was not involved in SURMOUNT-1. He attributed the plateau in BP reduction among tirzepatide-treated people to them hitting a wall in their BP nadir based on homeostatic limits. Dr. Sattar noted that most enrolled participants had normal BPs at entry based on the reported study averages.
“It’s hard to go lower, but the blood pressure reduction may be larger in people who start at higher pressure levels,” Dr. Sattar said in an interview.
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Dr. Darren McGuire
Another inferred cap on BP reductions in the trial hypothesizes that the individual clinicians who managed the enrolled patients may have cut back on other BP-lowering agents as the pressures of the tirzepatide recipients fell to relatively low levels, suggested Darren McGuire, MD, a cardiologist and professor at UT Southwestern Medical Center, who also was not involved in the SURMOUNT-1 study.
Incretin agonists as antihypertensive drugs
The substantial BP-lowering seen with tirzepatide, as well as with other incretin agonist agents, suggests a new way to think about BP control in people with overweight or obesity, Dr. Sattar said.
“Until now, we haven’t had tools where people lose so much weight. Now that we have these tools [incretin agonists as well as bariatric surgery], we see substantial blood pressure reductions. It makes you think we should use weight-loss agents to lower blood pressure rather than a beta-blocker or angiotensin-converting enzyme inhibitor; then we’d also produce all the other benefits from weight loss,” Dr. Sattar suggested.
Dr. de Lemos said he sees signals that the BP reductions caused by tirzepatide and the GLP-1 receptor agonists may go beyond just weight-loss effects.
“There appears to be a larger blood pressure reduction than anticipated based on the change in weight,” he said during his presentation. “GLP-1 is active in most vascular tissues, so these [receptor agonist] agents likely have vascular or cardiac effects, or even effects on other tissues that may affect blood pressure.”
Heart rate increases were usually modest
The experiences with GLP-1 receptor agonists also suggest that the heart rate increases seen with tirzepatide treatment in SURMOUNT-1 will not have long-term effects. “The [Food and Drug Administration] mandated this heart rate substudy to make sure that the increase in heart rate was not larger than what would be anticipated” with a GLP-1 receptor agonist, Dr. de Lemos explained.
SURMOUNT-1 had a treatment-stopping rule to prevent a person’s heart rate from rising beyond 10 bpm from baseline. “Trivial numbers” of patients experienced a heart rate increase of this magnitude, he said. If used in routine practice, Dr. de Lemos said that he would closely investigate a patient with a heart rate increase greater than 10 mm Hg. The average increase seen with the highest dose, about 4 bpm above baseline, would generally not be concerning.
Tirzepatide received U.S. marketing approval from the FDA in May 2022 for treating people with type 2 diabetes. In October 2022, the FDA gave tirzepatide “Fast Track” designation for the pending application for approval of an indication to treat people with overweight or obesity who match the entry criteria for SURMOUNT-1 and for the second pivotal trial for this indication, SURMOUNT-2. According to a statement from Eli Lilly, the company that is developing and markets tirzepatide (Mounjaro), the FDA’s decision on the obesity indication will remain pending until the SURMOUNT-2 results are available, which the company expects will occur in 2023.
SURMOUNT-1 and SURMOUNT-2 were sponsored by Lilly, the company that markets tirzepatide. Dr. de Lemos has been a consultant to Lilly as well as to Amgen, AstraZeneca, Janssen, Novo Nordisk, Ortho, Quidel Cardiovascular, and Regeneron. Dr. Sattar has financial ties to Lilly, Afimmune, Amgen, AstraZeneca, Boehringer Ingelheim, Hammi, Merck Sharpe & Dohme, Novartis, Novo Nordisk, Pfizer, Roche, and Sanofi-Aventis. Dr. McGuire has ties to Lilly as well as to Altimmune, Applied Therapeutics, Bayer, Boehringer Ingelheim, CSL Behring, Lexicon, Merck, Metavant, Novo Nordisk, and Sanofi.