tirzepatide

tirzepatide

What is tirzepatidee

tirzepatide is the first dual incretin agonist on the market, developed by Eli Lilly. The molecule simultaneously activates the GLP-1 and the GIP receptor. First approval came in 2022 in the US for type 2 diabetes (Mounjaro), obesity approval (Zepbound in USA, Mounjaro with obesity label in EU) followed in 2023.

Structurally, tirzepatid is a 39-amino acid peptide with C20 fatty acid anchor for albumin binding. CAS No: 2023788-19-2. Molecular weight: 4813.53 g/mol. The binding affinity is asymmetric: significantly stronger at the GIP receptor than at the GLP-1 receptor, which distinguishes the mechanism of action from classical dual agonists.

Mechanism of action

The GLP-1 proportion acts as with semaglutide: increase insulin secretion, lower glucagon, delay gastric emptying, centrally dampen appetite.

The GIP share is new. GIP (Glucose-dependent Insulinotropic Polypeptide) also acts insulinotropically, but additionally on fat cells. GIP activation appears to improve insulin sensitivity in adipose tissue and increase storage capacity, paradoxically leading to better metabolic flexibility. The exact role of the GIP effect is still the subject of research. One thing is clear: the combination has a stronger effect than GLP-1 alone.

In SURMOUNT-1 (Yesstreboff et al., NEJM, 2022), obesity patients without diabetes lost an average of 22.5 percent of their body weight weekly after 72 weeks under 15 mg. With diabetes, the reduction is typically 4 to 6 percentage points lower.

Areas of application in research

• Type 2 diabetes: Mono- or combination therapy, excellent HbA1c reduction (1.7 to 2.4 percentage points)
• Obesity: BMI ≥30 or ≥27 with comorbidity
• Obstructive sleep apnea: SURMOUNT-OSA, FDA approval for this indication 2024
• NASH/MASLD: SYNERGY-NASH study showed 51 to 62 percent NASH resolution at 52 weeks
• Heart failure with resulting ejection fraction (HFpEF): Summit study 2024 positive
• Cardiovascular outcomes: SURPASS-CVOT underway, results expected in 2025

Study situation

SURPASS program (diabetes, 10 studies) and SURMOUNT program (obesity, 6 studies) are the main axes. The data is extensive.

Highlights:

• SURPASS-2 (Frias et al., NEJM, 2021): tirzepatid 15 mg vs semaglutide 1 mg. HbA1c reduction 2.3 vs 1.9 percent, weight loss 11.2 vs 5.7 kg
• SURMOUNT-1 (2022): 22.5 percent weight loss in obesity without T2D
• SURMOUNT-2 (Garvey et al., Lancet, 2023): 15.7 percent weight loss in obesity plus T2D
• SURMOUNT-5 (Aronne et al., NEJM, 2025): Head-to-Head tirzepatide vs semaglutidee in obesity. tirzepatidee significantly superior (20.2 vs 13.7 percent)

Unclear remains: long-term safety over 5 years, effect on lean mass, possible neurocognitive effects of the GIP share.

Mixing (reconstitution)

Pharmaceutical products are ready-made pens (KwikPen) or single-can vials. Research lyophilisate typical sizes 5 mg, 10 mg, 15 mg, 30 mg, 50 mg:

• 30 mg Vial with 3 ml bacteriostatic water → 10 mg/ml
• 50 mg Vial with 2.5 ml → 20 mg/ml
• After mixing cooling 2 to 8 degrees, stability about 6 weeks

Dosage range (research data)

Established Escalation:

• Start 2.5 mg/week, subcutaneous
• After 4 weeks 5 mg
• Continue dosing every 4 weeks in 2.5 mg increments
• Maintenance doses: 5, 10, 15 mg (diabetes standard)
• Obesity goes up to 15 mg, in some studies up to 20 mg

Subcutaneous, weekly, same weekday.

Side effects

Profile similar to semaglutide, partly more pronounced due to stronger overall effect:

• Nausea (often in escalation phase)
• Diarrhoea (more common than semaglutide)
• Obstipation
• Reflux, belching
• Hypoglycaemia in combination with sulfonylureas
• Pancreatitis (rare, box warning)
• Gallbladder diseases
• Thyroid C cell tumor risk (analog GLP-1, box warning)
• Injection site reactions
• muscle mass loss (proportion of weight loss similar to semaglutide)

Half-Life and Pharmacokinetics

Elimination half-life: approximately 5 days. Steady-State after 4 weeks. Bioavailability subcutaneously about 80 percent. Metabolism via proteolytic cleavage, excretion renal and via faeces as metabolites.

No relevant CYP interactions. Caution with Oral contraceptives: delayed gastric emptying may affect absorption, therefore additional protection is recommended in the first 4 weeks after dose escalation.

Frequent questions

Is tirzepatide Better than semaglutidee? In direct comparison studies (SURPASS-2, SURMOUNT-5) yes, both in HbA1c and in weight loss. The effect is clinically relevant and consistent.

How much does Mounjaro cost in Germany? On private prescription about 280 to 320 euros for four weeks depending on the dose. Cash performance at T2D, obesity usually self-payers.

Can I drop Mounjaro abruptly? Possible, but rebound effect is pronounced. Studies show 50 to 70 percent regain within a year.

tirzepatide and alcohol? GLP-1 and GIP activation appear to lower alcohol cravings in some patients. Initial studies are underway for alcohol use disorders.

Why is tirzepatid in the EU as a pen, in the USA as a vial? Pure marketing decision, both forms pharmacologically identical.

Legal status U.S.

Status 2026: tirzepatide is approved as Mounjaro in Germany, Austria and Switzerland for T2D and obesity. Pharmacy required, medical prescription required. GKV reimbursement for T2D indication, for obesity self-payer.

Delivery situation 2026: largely stable after bottlenecks 2023/2024. Purchase outside the pharmacy is not covered by pharmaceutical law.

Related compounds

• semaglutideGLP-1 mono-agonist (Ozempic, Wegovy)
• retatrutideGLP-1/GIP/Glucagon triple agonist, phase 3
• survodutideGLP-1/Glucagon-Dual by Boehringer
• mazdutideTriple agonist from China (Innovent)
• cagrilintideAmylin analogue, in combination with semaglutide (CagriSema)

Note: All information is for research information only. These peptides are not approved as medicines in Germany. The contents do not replace medical advice. Application to humans is not legally covered in Germany.