The SURPASS trial program showed tirzepatide reduced HbA1c by up to 2.59% and body weight by up to 12.9 kg in type 2 diabetes, outperforming semaglutide in head-to-head comparison.
Up to 12.9 kg weight lossTirzepatide 15 mg weekly in the SURPASS trial program, alongside HbA1c reductions of up to 2.59%
What the researchers found
Across SURPASS 1–5 trials, tirzepatide (5, 10, 15 mg weekly) produced HbA1c reductions of 1.87–2.59% (20–28 mmol/mol) and body weight reductions of 6.2–12.9 kg. In SURPASS-2, tirzepatide exceeded semaglutide 1 mg on both glycemic and weight outcomes. Additional cardiometabolic benefits included reductions in blood pressure, visceral adiposity, and triglycerides. Safety was similar to the GLP-1 receptor agonist class with low hypoglycemia risk when used without insulin.
Why it matters
Tirzepatide represented a paradigm shift when approved — the first drug to target both GIP and GLP-1 receptors simultaneously. Its superior efficacy over semaglutide in head-to-head comparison challenged the notion that single-target GLP-1 drugs were optimal. The magnitude of weight loss (up to 12.9 kg) also blurred the line between diabetes treatment and weight management medication.
How the study worked
This is a narrative review summarizing the Phase 3 SURPASS clinical trial program (SURPASS 1–5), which evaluated once-weekly subcutaneous tirzepatide at three doses (5, 10, 15 mg) as monotherapy and combination therapy across diverse type 2 diabetes populations. Comparators included placebo, semaglutide, insulin degludec, and insulin glargine.
What this study cannot tell us
This is a narrative review, not a systematic review or meta-analysis. The SURPASS trials had relatively short durations for assessing long-term outcomes. Cardiovascular outcome data were not yet available at the time of this review. The semaglutide comparator was the 1 mg dose, not the higher 2.4 mg weight-loss dose. Gastrointestinal side effects, while manageable, remain a consideration.
How to read the evidence
This review summarizes Phase 3 randomized controlled trial data — the highest level of clinical evidence. The SURPASS program included large, well-designed trials with active comparators. However, this is a narrative review, not a systematic analysis.
When this study was published
Published in 2023, this review covers the foundational SURPASS trials that led to tirzepatide's FDA approval. Additional data on cardiovascular outcomes and other indications have since become available.
The bigger picture
Tirzepatide's dual mechanism (GIP + GLP-1) represents the next generation of incretin-based therapy. Its success has sparked development of triple agonists (GIP/GLP-1/glucagon) and positioned multi-receptor targeting as the future of metabolic disease treatment. The drug's investigation in heart failure, NASH, and obesity reflects the broader trend of peptide drugs addressing multiple cardiometabolic conditions simultaneously.
Questions still open
- How does tirzepatide compare to higher-dose semaglutide (2.4 mg) for weight loss and glycemic control?
- Will tirzepatide's cardiovascular outcome trial demonstrate superiority over GLP-1 receptor agonists for heart protection?
- What is the optimal long-term maintenance strategy — continued tirzepatide or transition to lower doses?
Common questions
How is tirzepatide different from semaglutide?
What are the main side effects of tirzepatide?
Read the original research
Tirzepatide for the treatment of adults with type 2 diabetes: An endocrine perspective.
Diabetes, obesity & metabolism, 25(1), 3-17
Citation
De Block, Christophe; Bailey, Clifford; Wysham, Carol; Hemmingway, Andrea; Allen, Sheryl Elaine; Peleshok, Jennifer. (2023). Tirzepatide for the treatment of adults with type 2 diabetes: An endocrine perspective.. Diabetes, obesity & metabolism, 25(1), 3-17. https://doi.org/10.1111/dom.14831