Mechanism of action
Tirzepatide binds and activates both the glucose-dependent insulinotropic polypeptide receptor (GIPR) and the GLP-1 receptor (GLP-1R). In the preclinical characterization (Coskun et al. 2018), the molecule showed binding affinity at GIPR comparable to native GIP and lower affinity at GLP-1R than native GLP-1, a deliberately imbalanced profile. GLP-1R engagement is associated in study models with glucose-dependent insulin secretion, suppression of glucagon release, delayed gastric emptying, and central appetite regulation via hypothalamic satiety circuits; the GIPR component has been linked to additional effects in adipose tissue, including adipocyte insulin sensitivity. The C20 fatty diacid side chain mediates albumin binding and extends the plasma half-life to approximately 120 hours, about 5 days (SURPASS-1, Eli Lilly).
State of evidence
The evidence base for tirzepatide is unusually broad for a peptide of this class. The in vitro receptor pharmacology and rodent models of the preclinical characterization (Coskun et al. 2018) were followed by phase 1 and phase 2 trials and two large phase 3 programs: SURPASS in type 2 diabetes, including the placebo-controlled SURPASS-1 trial and the head-to-head comparison with semaglutide (SURPASS-2), and SURMOUNT in obesity (SURMOUNT-1). The pharmaceutical product is approved as Mounjaro (type 2 diabetes; FDA 2022, EU marketing authorization via the EMA) and as Zepbound (chronic weight management; FDA 2023). Open questions include long-term effects beyond the trial durations, the course after discontinuation, and outcomes in populations not covered by the trial inclusion criteria. All of these data were generated with the pharmaceutical product under controlled clinical conditions; they permit no conclusions about the efficacy or safety of research-grade material.
Storage and handling
Lyophilized peptides are generally stored cool, dry, and protected from light; for long-term storage, the literature describes temperatures of 2 to 8 °C or below. After reconstitution, peptide solutions are typically kept refrigerated and used within a few days; repeated freeze-thaw cycles are avoided. No product-specific stability data exist for research-grade material.
Questions about the research
- What is tirzepatide studied for in research?
- Tirzepatide is studied primarily in metabolic research, in particular on the regulation of glucose metabolism and body weight. The clinical programs SURPASS (type 2 diabetes) and SURMOUNT (obesity) form the core of the published studies. Beyond that, the substance serves as a tool for mechanistic research into the contribution of the GIP receptor to the pharmacology of dual incretin agonists.
- What is the state of the evidence on tirzepatide?
- The substance has been characterized preclinically and studied in extensive phase 1 through phase 3 programs; the pharmaceutical product is approved as Mounjaro and Zepbound. This makes tirzepatide one of the most thoroughly documented peptides in its class. However, the data refer to the medicinal product under controlled trial conditions and cannot be transferred to research-grade material.
Sources
- Coskun et al., Mol Metab 2018DOI: 10.1016/j.molmet.2018.09.009PMID: 30473097
- Rosenstock et al., Lancet 2021 (SURPASS-1)DOI: 10.1016/S0140-6736(21)01324-6PMID: 34186022
- Frías et al., NEJM 2021 (SURPASS-2)DOI: 10.1056/NEJMoa2107519PMID: 34170647
- Jastreboff et al., NEJM 2022 (SURMOUNT-1)DOI: 10.1056/NEJMoa2206038PMID: 35658024
- EMA: Mounjaro (EPAR)