Semaglutide. Tirzepatide. Sermorelin. Octreotide. If you've spent any time reading about peptide drugs, you've probably noticed these names share suspicious-looking endings. That's not a coincidence, it's a deliberate naming system, and understanding it can help make sense of an otherwise bewildering drug landscape.
What INN Names Are
Most drug names fall into two categories: a brand name chosen by the manufacturer for marketing (Ozempic, Wegovy, Mounjaro) and a nonproprietary, or generic, name assigned through a formal international process. That generic name is called the International Nonproprietary Name, or INN, coordinated by the World Health Organization. In the United States, a closely related process run through the American Medical Association's United States Adopted Names Council typically produces the same or a very similar name. The goal of the system is to give every drug substance one internationally recognized generic name, distinct from any brand, that conveys some information about the drug's chemical or pharmacological class just from its ending.
The Master Stem for Peptides
Within the INN system, peptide and glycopeptide drugs generally share the broad suffix "-tide" somewhere in their name, marking them as belonging to this general structural class. From there, more specific "stems" narrow the classification further, based on a drug's particular mechanism or target.
Common Peptide Stems and What They Signal
Several stems show up repeatedly across peptide drug names covered on this site. The stem "-glutide" marks glucagon-like peptide-1 (GLP-1) analogues, which is why semaglutide, liraglutide, and dulaglutide all share that ending despite being distinct molecules from different manufacturers. The stem "-relin" identifies a broader category of pituitary hormone-release-stimulating peptides, with the narrower substem "-morelin" specifically marking growth-hormone-release-stimulating peptides, covering drugs like sermorelin, tesamorelin, and ipamorelin. The stem "-reotide" identifies somatostatin receptor agonists and antagonists, covering drugs like octreotide and lanreotide. Oxytocin-related peptides carry the stem "-tocin," while vasopressin-related peptides use "-pressin." Natriuretic peptides use the stem "-ritide."
Why This System Exists
The practical purpose of stem-based naming is to let a prescriber, pharmacist, or researcher make an educated guess about a drug's pharmacological class just from its generic name, even before looking anything up. Seeing "-glutide" in a name is a strong hint you're looking at a GLP-1 analogue, the same way seeing "-cillin" in a drug name suggests a penicillin-class antibiotic. That's a genuinely useful signal in a field where hundreds of peptide drugs and candidates are in development simultaneously.
What the Naming System Doesn't Tell You
It's important not to over-read what a stem communicates. A shared stem groups drugs by general pharmacological family, not by approval status, efficacy, or safety profile. Semaglutide and a research-chemical GLP-1 analogue sold outside FDA channels could, in principle, both end up with "-glutide" somewhere in an assigned or informal name, despite being in entirely different regulatory categories. The INN and USAN systems classify chemistry and mechanism; they say nothing about whether the FDA has approved a given drug, and a peptide's naming stem is never a substitute for checking its actual, separately established regulatory status.
The Bottom Line
Peptide drug names look intimidating, but the endings follow a real, internationally coordinated system designed to make drug classes recognizable at a glance. Learning a handful of common stems, "-glutide," "-relin," "-reotide," "-tocin," and "-pressin" among them, is a small piece of pharmacology literacy that makes the broader peptide drug landscape noticeably easier to navigate.