Tirzepatide evidence base: what has reported and what has not

As of September 14, 2026, tirzepatide — sold as Mounjaro for type 2 diabetes and Zepbound for weight management and obstructive sleep apnea — has one of the largest published trial records of any metabolic drug. It also has a sizable list of studies that have finished enrolling, or are still running, with no public results.

On the reported side, results are available across the diabetes program (SURPASS 1 through 6, plus SURPASS J-mono, J-combo, AP-Combo, PEDS, SWITCH, EARLY, CN-MONO and the cardiovascular outcomes trial) and the obesity program (SURMOUNT 1 through 5, SURMOUNT-OSA, SURMOUNT-J, SURMOUNT-CN and SURMOUNT-MAINTAIN). Two other trials outside those families have also read out: SUMMIT, in heart failure with preserved ejection fraction, and SYNERGY-NASH, in metabolic dysfunction-associated steatohepatitis.

That published base is what the current U.S. labeling rests on. Zepbound is approved, alongside a reduced-calorie diet and more physical activity, to reduce excess body weight and maintain that reduction long term in adults with obesity or adults with overweight plus at least one weight-related condition, and to treat moderate to severe obstructive sleep apnea in adults with obesity ^[5]. The label carries a boxed warning about thyroid C-cell tumors seen in rats, and states it is unknown whether tirzepatide causes these tumors, including medullary thyroid carcinoma, in humans ^[5].

What has not reported

Five tirzepatide studies remain outstanding.

SURMOUNT-MMO (NCT05556512) is the morbidity and mortality trial in adults with obesity — the study designed to test whether tirzepatide reduces hard outcomes such as heart attacks, strokes and death in people who do not necessarily have diabetes ^[1]. Its estimated completion is October 2027, which makes it the longest wait on the list.

SURPASS-T1D-1 and SURPASS-T1D-2 would be the first randomized data on tirzepatide in type 1 diabetes, a population the drug is not approved for. Both carry estimated completion dates of November 2026 ^[2].

TRIUMPH-5 (NCT06662383) is a head-to-head trial of retatrutide, an investigational Eli Lilly triple agonist, against tirzepatide in adults with obesity ^[3]. Its estimated completion is also November 2026. It is one of the few trials that will directly compare tirzepatide with a newer molecule rather than with placebo or an older drug.

Two studies are listed as completed but have not published: TREASURE-CKD (NCT05536804), in people with overweight or obesity and chronic kidney disease with or without type 2 diabetes ^[4], and SURPASS-CN-INS, an insulin-combination study in China.

Why it matters for patients

The gap between "studied" and "proven" matters for coverage and for counseling. Semaglutide's Wegovy label gained a cardiovascular risk-reduction indication after its outcomes trial reported; tirzepatide does not have an equivalent obesity outcomes result yet, because SURMOUNT-MMO has not read out. That means questions such as whether tirzepatide lowers heart attack and stroke risk in people with obesity but without diabetes are not yet answered by published evidence.

The unreported kidney trial matters for a similar reason. Chronic kidney disease is common in people with obesity and type 2 diabetes, and TREASURE-CKD is finished but silent ^[4]. Until results appear, there is no randomized tirzepatide data in that group to weigh.

Type 1 diabetes is a third gap. Tirzepatide is not approved for type 1 diabetes, and the two SURPASS-T1D trials are what would inform any future discussion there.

Meanwhile, the label keeps changing based on accumulating safety data, not just trial readouts. Recent changes listed on the Zepbound prescribing information include a revised warning on severe gastrointestinal adverse reactions in February 2026, removal of the suicidal behavior and ideation warning in February 2026, and a new warning on diabetic retinopathy complications in patients with type 2 diabetes in August 2026 ^[5].

What happens next

• November 2026: estimated completion for SURPASS-T1D-1, SURPASS-T1D-2 ^[2] and TRIUMPH-5 ^[3].
• October 2027: estimated completion for SURMOUNT-MMO ^[1].

Estimated completion dates on ClinicalTrials.gov are projections and often move. Completion also is not publication: results can follow months later, as the still-unreported TREASURE-CKD shows ^[4]. No publication dates for TREASURE-CKD or SURPASS-CN-INS have been announced.