Triple agonist (revision 12)
Old revision·20:21, 6 Mar 2025·CouplingCillian
| Triple agonistDrug class | |
|---|---|
| Usual receptors | GIP, GLP-1 and glucagon |
| Leading example | Retatrutide |
| Design constraint | A fixed three-way potency ratio |
| Topic infobox · conventions | |
A triple agonist is a single engineered peptide that activates three receptors of the glucagon-secretin family — conventionally the receptors for GIP, GLP-1 and glucagon. Retatrutide is the most advanced example and is investigational.[1]
The design extends the logic of the dual agonists by one receptor, and multiplies the constraints accordingly: the sequence must retain activity at three targets in a ratio fixed by chemistry, and that ratio must remain appropriate across the whole dose range.[1]
Adding glucagon-receptor agonism introduces an effect that opposes the others glycaemically, in exchange for increased energy expenditure and reduced hepatic fat. The balance is the central difficulty. See Glucagon.[2]
Why three receptors
[edit]Each added receptor is intended to contribute a mechanism the others do not. GLP-1 agonism supplies appetite suppression and glucose-dependent insulin secretion; GIP agonism appears to improve tolerability and contributes adipose-tissue effects; glucagon agonism raises energy expenditure and mobilises hepatic fat.[1]
Because the receptors share a common architecture and their ligands a common precursor family, a peptide can be engineered to engage all three — see Proglucagon — but the sequence space in which all three activities coexist at usable ratios is narrow.[2]
Reported potency ratios are assay-dependent and are not comparable between publications, a caution that applies with more force here because three numbers are being compared rather than two.[1]
Consequences of the glucagon arm
[edit]Two observations in the phase 2 data are attributable to glucagon-receptor agonism: a dose-dependent heart-rate increase larger than that seen with GLP-1 monotherapy, and transient rises in fasting glucose at low doses in participants with diabetes.[2]
The second is the design's predicted failure mode. At low total dose the glucagon component is not yet offset by sufficient GLP-1 agonism, so glycaemia worsens before it improves — which is why escalation schedules for these compounds are long.[1]
Long-term consequences of sustained heart-rate elevation are the question phase 3 exists to answer, and no answer is available yet. See TRIUMPH trial programme.[2]
See also
References
- ^ a b c d e Coskun T, Urva S, Roell WC, et al. "LY3437943, a novel triple glucagon, GIP, and GLP-1 receptor agonist." Cell Metabolism 34(9):1234–1247 (2022). PMID 35985340.
- ^ a b c d Jastreboff AM, Kaplan LM, Frías JP, et al. "Triple-hormone-receptor agonist retatrutide for obesity — a phase 2 trial." New England Journal of Medicine 389(6):514–526 (2023). PMID 37366315.