Tirzepatide

The landmark SURMOUNT-1 trial enrolled 2,539 adults with obesity or overweight without diabetes. After 72 weeks, average body-weight changes were approximately: 5 mg, −15.0%; 10 mg, −19.5%; 15 mg, −20.9%; placebo, −3.1%.

At the 15-mg dose, 57% of participants achieved at least a 20% reduction in body weight, compared with 3% receiving placebo. These results represent substantially stronger evidence than the preclinical or small early-phase evidence available for many investigational weight-management peptides.

In November 2023, FDA approved tirzepatide under the brand name Zepbound for chronic weight management in adults with obesity, or overweight plus at least one weight-related medical condition. The approved use is in combination with a reduced-calorie diet and increased physical activity.

The current FDA label also specifically states that Zepbound is intended to reduce excess body weight and maintain weight reduction long term. This distinguishes tirzepatide from experimental peptides marketed for “fat burning” without an approved weight-management indication.

Tirzepatide was originally FDA-approved as Mounjaro in May 2022 for type 2 diabetes. As of the current 2026 labeling, Mounjaro is indicated to improve glycemic control, along with diet and exercise, in adults and pediatric patients age 10 and older with type 2 diabetes.

The SURPASS-2 trial compared tirzepatide with once-weekly semaglutide in 1,879 adults with type 2 diabetes. At 40 weeks, average HbA1c changes were approximately: 5 mg tirzepatide, −2.01 percentage points; 10 mg, −2.24; 15 mg, −2.30; semaglutide 1 mg, −1.86. Body-weight reductions were also greater in the tirzepatide groups in that particular head-to-head trial.

Importantly, those findings apply to the specific doses, population and semaglutide formulation studied. They should not be generalized into a claim that tirzepatide is universally “better” for every patient.

One of the most important newer developments occurred on December 20, 2024, when FDA approved Zepbound for moderate-to-severe obstructive sleep apnea in adults with obesity. This was the first FDA-approved medication for this specific OSA population.

The approval was based on two randomized trials involving 469 adults with obesity and moderate-to-severe OSA. After 52 weeks, tirzepatide produced clinically meaningful reductions in the apnea-hypopnea index (AHI) compared with placebo, both among people using positive airway pressure therapy and among those not using PAP.

The current Zepbound label lists treatment of moderate-to-severe OSA in adults with obesity as an FDA-approved indication.

An extended analysis of SURMOUNT-1 followed participants with obesity and prediabetes for 176 weeks — more than three years. At week 176, mean body-weight changes were approximately: 5 mg, −12.3%; 10 mg, −18.7%; 15 mg, −19.7%; placebo, −1.3%.

During the treatment period, type 2 diabetes developed in approximately 1.3% of tirzepatide-treated participants versus 13.3% receiving placebo. These results provide strong evidence that tirzepatide can substantially reduce progression to type 2 diabetes in the studied population.

However, tirzepatide does not currently have a separate FDA indication specifically labeled as “diabetes prevention.” That distinction should remain clear on an educational website.

Tirzepatide has also produced notable results in people with obesity-related heart failure with preserved ejection fraction (HFpEF). The SUMMIT trial enrolled 731 patients with obesity and HFpEF.

Cardiovascular death or worsening heart failure occurred in 9.9% of participants receiving tirzepatide versus 15.3% receiving placebo. Participants receiving tirzepatide also experienced improved health-status scores.

This represents meaningful human clinical evidence. However, the current Zepbound FDA label lists weight management and obstructive sleep apnea — not HFpEF — as its approved indications. Therefore, heart-failure findings should be described as clinical research rather than an FDA-approved indication.