Tirzepatide: Science, studies and safety data

Peptology · 2026-06-04

Tirzepatide: a scientific review of weight-loss efficacy and a comparative analysis with Semaglutide

Tirzepatide is the first-in-class dual GIP and GLP‑1 receptor agonist, developed for the treatment of type 2 diabetes and also studied for weight management. The molecule combines the effects of two incretin pathways, resulting in stronger regulation of appetite and glucose metabolism.

Clinical trial results: body weight

Results from SURMOUNT‑1 (72 weeks)

• 5 mg: ~‑15% weight loss

• 10 mg: ~‑19.5%

• 15 mg: ~‑20.9%
  
  
  

Long-term effect (88 weeks)

• Up to 25.3 % mean weight reduction versus 9.9 % with placebo.
  
  

Probability of ≥5/10/15 % weight loss

• Tirzepatide significantly increases the chance of achieving ≥15% weight loss compared with Semaglutide.
  
  

Other trial findings

Glycaemic control

• Tirzepatide leads to a greater reduction in HbA1c compared with Semaglutide 1 mg.

Cardiovascular and cognitive effects

• GLP‑1 therapies, including Tirzepatide, are associated with reduced risk of stroke and dementia.

Weight maintenance

• 89.5 % of patients retain ≥80 % of lost weight on long-term follow-up.
  
  

Tirzepatide versus Semaglutide: results

Clinical data (SURMOUNT‑5)

• Mean weight loss after 72 weeks: 20 % with Tirzepatide versus 14 % with Semaglutide.

• Patients with ≥25 % loss: 32 % with Tirzepatide versus 16 % with Semaglutide.

Tolerance and side effects

• Similar profile: most commonly nausea, diarrhea, constipation. Lower discontinuation rate with Tirzepatide.
  
  
  
  

Safety

• Common GI effects: nausea, vomiting, diarrhea.

• Potential risk of C‑cell thyroid tumors (as with Semaglutide).
  
  

Conclusion

Tirzepatide is a dual GIP and GLP‑1 receptor agonist. In SURMOUNT‑1 the mean weight reduction reached up to ~21% at 72 weeks, and in the head-to-head SURMOUNT‑5 trial it was greater than with semaglutide (20% versus 14%). These are clinical trial data; the tirzepatide offered by Peptology is a research peptide intended for laboratory use only.

Frequently asked questions

How does tirzepatide differ from semaglutide?

Semaglutide activates only the GLP‑1 receptor, while tirzepatide also activates the GIP receptor (dual agonist).

Which trial compared tirzepatide with semaglutide directly?

SURMOUNT‑5 (72 weeks): mean weight loss of 20% with tirzepatide versus 14% with semaglutide.

Did the trials include people without diabetes?

Yes, the SURMOUNT-1 trial included people with obesity who did not have diabetes.