Peptide Drug-Class Taxonomy
27 commonly discussed peptides, organized into their pharmacological classes by mechanism — so you can see at a glance what a peptide actually is and how it works.
Medically reviewed by Charles Kamen, MD, board-certified neurologist ·
Commonly discussed peptides fall into about ten pharmacological classes by mechanism — incretin mimetics (GLP-1 and dual/triple agonists), GHRH analogs, growth-hormone secretagogues, melanocortin receptor agonists, thymic/immune peptides, and more. Grouping by mechanism is the clearest way to understand them — and it surfaces a common error: not everything marketed as a “peptide,” such as MK-677, actually is one. This page describes classification and mechanism only — no doses, no efficacy claims.
Peptides by class
Each class, its mechanism, and its members — with FDA status and whether each is a true peptide.
| Peptide | Class | Mechanism | FDA-approved? | True peptide? |
|---|---|---|---|---|
| Semaglutide | Incretin mimetics (GLP-1 & dual/triple agonists) | GLP-1 receptor agonist | Yes | Yes |
| Liraglutide | Incretin mimetics (GLP-1 & dual/triple agonists) | GLP-1 receptor agonist | Yes | Yes |
| Dulaglutide | Incretin mimetics (GLP-1 & dual/triple agonists) | GLP-1 receptor agonist (once-weekly) | Yes | Yes |
| Exenatide | Incretin mimetics (GLP-1 & dual/triple agonists) | Exendin-4–based GLP-1 receptor agonist (first in class) | Yes | Yes |
| Tirzepatide | Incretin mimetics (GLP-1 & dual/triple agonists) | Dual GIP / GLP-1 receptor agonist | Yes | Yes |
| Retatrutide | Incretin mimetics (GLP-1 & dual/triple agonists) | Triple GLP-1 / GIP / glucagon receptor agonist (investigational) | No | Yes |
| Tesamorelin | GHRH analogs | Full GHRH analog — the only FDA-approved GHRH analog | Yes | Yes |
| Sermorelin | GHRH analogs | GHRH(1–29) fragment; prior approved product withdrawn ~2008 | No | Yes |
| CJC-1295 | GHRH analogs | Modified long-acting GHRH analog | No | Yes |
| Ipamorelin | Growth-hormone secretagogues / GHRPs (ghrelin mimetics) | Selective pentapeptide GHS-R1a agonist | No | Yes |
| GHRP-2 | Growth-hormone secretagogues / GHRPs (ghrelin mimetics) | GHS-R1a agonist | No | Yes |
| GHRP-6 | Growth-hormone secretagogues / GHRPs (ghrelin mimetics) | GHS-R1a agonist (also stimulates appetite) | No | Yes |
| Hexarelin | Growth-hormone secretagogues / GHRPs (ghrelin mimetics) | High-amplitude GHS-R1a agonist (also binds CD36) | No | Yes |
| Ibutamoren (MK-677) | Growth-hormone secretagogues / GHRPs (ghrelin mimetics) | NON-peptide (sulfonamide), orally active GHS-R1a agonist | No | No (non-peptide) |
| Bremelanotide (PT-141) | Melanocortin receptor agonists | MC3R/MC4R-biased agonist; studied for sexual desire (FDA-approved as Vyleesi) | Yes | Yes |
| Setmelanotide | Melanocortin receptor agonists | Selective MC4R agonist; rare genetic obesity | Yes | Yes |
| Afamelanotide | Melanocortin receptor agonists | MC1R agonist (FDA-approved as Scenesse) | Yes | Yes |
| Melanotan II | Melanocortin receptor agonists | Non-selective melanocortin agonist (unapproved) | No | Yes |
| Thymosin alpha-1 | Thymic / immune peptides | Immunomodulator (approved in 30+ countries, not the U.S.) | No | Yes |
| Thymosin beta-4 / TB-500 | Thymic / immune peptides | Actin-binding repair regulator; TB-500 is a synthetic fragment, not the full protein | No | Yes |
| BPC-157 | Body-protective / tissue-repair | Gastric-juice–derived pentadecapeptide; pro-angiogenic in animal studies | No | Yes |
| GHK-Cu | Cosmetic / copper peptides | Copper tripeptide-1; not FDA-approved as a drug | No | Yes |
| Semax | Nootropic / regulatory peptides | ACTH(4–10) analog; studied for neuroprotection | No | Yes |
| Selank | Nootropic / regulatory peptides | Tuftsin analog; studied as an anxiolytic | No | Yes |
| MOTS-c | Mitochondrial-derived peptides | Mitochondrial-derived AMPK-linked metabolic regulator | No | Yes |
| Humanin | Mitochondrial-derived peptides | Mitochondrial-derived cytoprotective peptide | No | Yes |
| Epitalon | Pineal / telomere peptides | AEDG tetrapeptide; telomerase induction reported in cell cultures | No | Yes |
Three corrections this taxonomy makes: (1) MK-677 (ibutamoren) is a non-peptide sulfonamide, grouped here only because it shares the ghrelin-receptor mechanism; (2) TB-500 is a synthetic fragment of thymosin β-4, not the full native protein; (3) tesamorelin is the only FDA-approved GHRH analog — sermorelin’s earlier approved product was withdrawn, and CJC-1295 was never approved.
How this taxonomy is maintained: compiled and reviewed by Charles Kamen, MD from pharmacology literature (PubMed/PMC), FDA records, and structural references. 9 of the 27 listed compounds are FDA-approved finished drugs.
Educational reference, not medical advice.“Studied for” describes a research context, not an endorsement, and this page makes no efficacy, safety, or treatment claims and publishes no doses. Decisions about any peptide should be made with a licensed physician.
Peptide Class FAQ
What class is BPC-157?
BPC-157 is a body-protective / tissue-repair synthetic peptide — a gastric-juice–derived pentadecapeptide. It forms its own category, distinct from the thymosins it is often stacked with, and it is not FDA-approved.
Is MK-677 a peptide?
No. MK-677 (ibutamoren) is a non-peptide sulfonamide that is orally active. It is grouped with peptides because it shares the GHS-R1a (ghrelin) mechanism of the injectable growth-hormone secretagogues, but structurally it is not a peptide.
What is the difference between a GHRH analog and a GHRP?
GHRH analogs (sermorelin, tesamorelin, CJC-1295) act on the GHRH receptor. GHRPs and ghrelin mimetics (ipamorelin, GHRP-2, GHRP-6, hexarelin) act on the separate GHS-R1a receptor. Because they work through two different pathways, they are sometimes studied in combination.
Which of these peptides are FDA-approved?
Semaglutide, liraglutide, dulaglutide, exenatide, tirzepatide, tesamorelin, bremelanotide, setmelanotide, and afamelanotide are FDA-approved. Sermorelin’s prior approved product was withdrawn; retatrutide is investigational; the remaining compounds are not FDA-approved finished drugs.
Related reading: Which peptides are FDA-approved? · GLP-1 medications compared · Peptide evidence-grade index
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