Agonist
An agonist is a molecule that binds to a receptor and switches it on, starting the cell response that receptor controls. If a receptor is a lock, an agonist is a key that turns it.
Where the word comes from
Agonist comes from the Greek agōnistēs, “a contestant or combatant,” from agōn, “a contest” — the same root that gives English “agony,” originally the struggle of a fight. Antagonist is the older English word: antagōnistēs, “the opponent in the contest.” Pharmacology borrowed the pair in the first half of the 1900s, as receptor theory matured, to name the molecule that acts and the molecule that opposes it.
What it means here
The opposite is an antagonist — a key that fits the lock but will not turn, blocking other keys instead. Published research describes many peptides in this catalog by their agonist role: which receptor they turn on, and how strongly. Some compounds are studied as agonists at several receptors at once; retatrutide is described in its published Phase 2 trial as a triple-hormone-receptor agonist. Naming a compound an agonist describes its mechanism at a receptor in a study system — it says nothing about outcomes in a person.
Words you’ll see together
- antagonist — the blocker; binds the receptor but does not switch it on
- partial agonist — switches the receptor on, but never to its full response
- selective — acts on one receptor while mostly ignoring its relatives
- potency — how little compound an assay needs to produce the receptor response
- EC50 — the concentration giving half the maximum response in a lab assay
Related terms
- Receptor — the lock; an agonist has no meaning without one
- Melanocortin receptor — a receptor family with several studied agonists in this catalog
- GHRH — a natural signal whose receptor several catalog peptides are studied against
- Peptide — many agonists studied in this field are peptides
Where it appears in our catalog
- Retatrutide — described in published trials as a triple-hormone-receptor agonist
- SLU-PP-332 — studied as a synthetic agonist of ERR receptors in mouse models
- Ipamorelin — studied as a selective agonist of the ghrelin receptor
References
- Jastreboff AM et al. (2023). Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. NEJM 389(6):514–526. PMID 37366315 · DOI 10.1056/NEJMoa2301972
- Billon C et al. (2024). A Synthetic ERR Agonist Alleviates Metabolic Syndrome. Journal of Pharmacology and Experimental Therapeutics. PMID 37739806
