Peptide encyclopedia
7 of 20 peptides match the filters. Each entry carries mechanism, route of administration, half-life, legal status in your jurisdiction, and the primary sources backing every claim.
- Compounds
- 20
- Source links
- 39
- Therapeutic classes
- 9
F·Filter
Reset all01·Sexual function
PT-141
Also: Bremelanotide, Vyleesi, et al.
PT-141, marketed as bremelanotide and approved as Vyleesi, is a cyclic heptapeptide melanocortin receptor agonist developed from the α-melanocyte-stimulating hormone (α-MSH) family. It is a non-selective melanocortin agonist with activity at MC1, MC3, MC4, and MC5 receptors; the MC4 receptor activity, particularly in the central nervous system, is the principal mechanism for sexual-desire and arousal effects. Unlike PDE5 inhibitors (sildenafil, tadalafil), which act peripherally on the vasculature of erectile tissue, PT-141 acts centrally — in the hypothalamic and other CNS pathways that regulate sexual desire and arousal — making the mechanism more upstream and the experiential profile distinct. The cyclic structure was engineered for stability against enzymatic degradation, supporting the as-needed subcutaneous dosing profile of the FDA-approved formulation ([Kingsberg et al., *Obstet Gynecol* 2019, 134:899–908](https://doi.org/10.1097/AOG.0000000000003500)).
Prescription only
02·Metabolic / GLP-1
Retatrutide
Also: LY3437943
Retatrutide is a synthetic peptide engineered as a balanced agonist of three receptors: the glucose-dependent insulinotropic polypeptide (GIP) receptor, the glucagon-like peptide 1 (GLP-1) receptor, and the glucagon receptor ([Jastreboff et al., *N Engl J Med* 2023, 389:514–526](https://doi.org/10.1056/NEJMoa2301972)). The first two receptors share their incretin mechanism with tirzepatide and semaglutide, respectively; the addition of glucagon-receptor agonism is what distinguishes retatrutide and is hypothesized to add a pro-energy-expenditure component to the appetite-suppressive and insulin-sensitizing effects of the two incretins. Mechanistically, glucagon-receptor agonism increases hepatic glucose output, mobilizes lipids, and raises basal energy expenditure — a combination that, balanced correctly against the incretin signals, is intended to drive weight loss through both reduced energy intake and increased energy turnover. The fatty-acid modification for albumin binding produces a roughly week-long pharmacokinetic profile suited to weekly dosing.
Prescription only
03·Mitochondrial
SS-31
Also: Elamipretide, Bendavia, et al.
SS-31, marketed as elamipretide, is a four-amino-acid peptide engineered by Hazel Szeto and Peter Schiller at Cornell to selectively concentrate in the inner mitochondrial membrane and bind cardiolipin — the unique phospholipid that organizes the electron transport chain and is exclusively localized to mitochondrial inner membranes. The molecule's structure (D-Arg-2',6'-dimethylTyr-Lys-Phe-NH2) combines alternating aromatic and basic residues with a D-stereochemistry N-terminal arginine that produces 1,000- to 5,000-fold concentration in the inner mitochondrial membrane relative to extracellular space. By stabilizing cardiolipin and supporting electron-transport-chain organization, SS-31 has been reported to improve mitochondrial respiration, reduce reactive oxygen species production under stress, and protect mitochondria in models of ischemia-reperfusion injury, heart failure, and primary mitochondrial disease. The mechanism is structural and pharmacological — direct organelle targeting — rather than receptor agonism, which distinguishes it sharply from every other peptide on this site.
Prescription only
04·Metabolic / GLP-1
Semaglutide
Also: Ozempic, Wegovy, et al.
Semaglutide is a 31-amino-acid analog of glucagon-like peptide-1 (GLP-1) with two structural modifications: an α-aminoisobutyric acid substitution at position 8 that resists degradation by DPP-4, and a C18 fatty acid chain attached at position 26 through a γ-glutamic acid spacer that binds plasma albumin and extends the half-life to about a week ([Lau et al., *J Med Chem* 2015, 58:7370–80](https://doi.org/10.1021/acs.jmedchem.5b00726)). It acts as a full agonist at the GLP-1 receptor, which is expressed on pancreatic β-cells, on enteric neurons, and on hypothalamic and brainstem appetite-regulating circuits. Three downstream effects matter clinically: glucose-dependent insulin secretion, slowed gastric emptying, and centrally mediated appetite suppression. The central effect is the dominant driver of weight loss, not the peripheral metabolic ones.
Prescription only
05·GH secretagogue
Tesamorelin
Also: Egrifta, Egrifta SV, et al.
Tesamorelin is a 44-amino-acid analog of human growth-hormone-releasing hormone (GHRH) with a trans-3-hexenoyl modification on the N-terminal Tyr¹ that confers resistance to dipeptidyl-aminopeptidase-IV degradation ([Ferdinandi et al., *Basic Clin Pharmacol Toxicol* 2007, 100:49–58](https://doi.org/10.1111/j.1742-7843.2007.00008.x)). Once injected subcutaneously, it binds the GHRH receptor on pituitary somatotrophs and triggers pulsatile growth hormone release, which in turn drives IGF-1 production in the liver. Plasma half-life is roughly 26 to 38 minutes — short enough that GH and IGF-1 stay broadly within their normal pulsatile pattern rather than being chronically elevated, which is the safety story the FDA reviewed.
Prescription only
06·Immune
Thymosin α-1
Also: Thymalfasin, Zadaxin, et al.
Thymosin α-1 is a 28-amino-acid acidic peptide first isolated from the thymus and now produced synthetically as thymalfasin. It is an immunomodulator rather than an immunostimulant — the published activity profile is heterogeneous across cell types, with effects on T-cell maturation and differentiation, dendritic-cell function, natural killer cell activity, regulatory cytokine balance, and TLR-mediated innate immune signaling ([Dominari et al., *World J Virol* 2020, 9:67–78](https://doi.org/10.5501/wjv.v9.i5.67)). The clinical development arc has tracked these mechanisms: early use in chronic viral hepatitis (where T-cell exhaustion is part of the disease biology), expansion into sepsis and severe infections, adjuvant use with vaccines in immunosenescent populations, and most recently a wave of interest in long-COVID and post-viral immune dysregulation. The peptide does not act through a single receptor pathway; it is best understood as a fine-tuning agent for the adaptive immune system rather than a directional stimulant.
Prescription only
07·Metabolic / GLP-1
Tirzepatide
Also: Mounjaro, Zepbound, et al.
Tirzepatide is a 39-amino-acid synthetic peptide engineered from the native glucose-dependent insulinotropic polypeptide (GIP) backbone, with a C20 fatty diacid chain attached via a γ-glutamic-acid / OEG linker to a Lys residue for albumin binding ([Jastreboff et al., *N Engl J Med* 2022, 387:205–216](https://doi.org/10.1056/NEJMoa2206038)). It activates both the GIP and GLP-1 receptors as a full or near-full agonist; the dual incretin engagement is the molecular signature that distinguishes it from semaglutide and the rest of the GLP-1 monoagonist class. Downstream effects span the same three mechanisms as GLP-1: glucose-dependent insulin secretion, slowed gastric emptying, and central appetite suppression. The GIP component contributes additional metabolic effects — including modulation of adipose insulin sensitivity and potential alteration of nausea-pathway signaling — that may explain part of the larger weight-loss magnitude relative to GLP-1 monoagonism, though the contribution of each receptor to clinical effect is still being parsed in the literature.
Prescription only