Introduction to Tirzepatide
Tirzepatide (brand name Mounjaro for T2D; Zepbound for obesity) is a 39-amino acid synthetic peptide that co-activates both GLP-1 (glucagon-like peptide-1) and GIP (glucose-dependent insulinotropic polypeptide) receptors. It represents the first approved dual incretin receptor agonist and the most efficacious compound for weight loss in clinical research.
Molecular Properties
- Molecular weight: ~4,813.5 Da
- Structure: 39-AA GIP analogue with GLP-1R binding modifications; C20 fatty diacid at K20
- Half-life: ~5 days
- Receptor: GLP-1R + GIPR (dual)
- Bioavailability: ~80% subcutaneous
Dual Agonist Mechanism
GLP-1R Activation
- Glucose-dependent insulin secretion
- Glucagon suppression
- Slowed gastric emptying
- Hypothalamic satiety signaling
- Cardiovascular protection
GIPR Activation
- Potentiated insulin secretion (GIP is the primary post-meal incretin in humans)
- Direct adipocyte GIPR effects on lipolysis/lipogenesis
- Reduction of GLP-1-associated nausea (hypothesized)
- Bone and cardiac protection
- Central appetite amplification
Clinical Data Summary (SURMOUNT)
| Trial | Population | Weight Loss (15mg) | Duration |
| SURMOUNT-1 | Obesity | −20.9% | 72 wks |
| SURMOUNT-2 | T2D | −15.7% | 72 wks |
| SURMOUNT-3 | After IBT | −26.6% total | 84 wks |
| SURMOUNT-4 | Maintenance | −21.8% | 88 wks |
| SURPASS-CVOT | T2D + CVD | −15% vs. dul | 3.4 yrs |
Reconstitution Protocol
15mg vial: Add 3–5mL BAC water (3–5mg/mL) 30mg vial: Add 6mL BAC water (5mg/mL) 60mg vial: Add 6–12mL BAC water (5–10mg/mL)
Swirl gently until fully dissolved. Store at 2–8°C. Use within 4–6 weeks.
Research Applications
- Dual incretin receptor biology: GLP-1R vs. GIPR contribution studies using receptor-selective antagonists
- Metabolic research: Superior weight loss model vs. GLP-1 agonists alone
- Adipose biology: GIPR-mediated adipocyte effects on fat metabolism
- Comparative pharmacology: vs. semaglutide for GLP-1-only effects
- Cardiovascular: SURPASS-CVOT data for cardiac research context