Peptide categories

The anti-inflammatory peptide class spans small NF-κB-targeting tripeptides (KPV), broader cytokine modulators (BPC-157, GHK-Cu), and direct anti-fibrotic compounds (AC-SDKP, pentosan polysulfate).

Antimicrobial peptide research focuses on cationic amphipathic peptides that disrupt anionic microbial membranes while modulating host immune signalling. LL-37 is the principal mammalian example.

Cognitive research peptides act principally through upregulation of brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), and related neurotrophins, or through direct receptor agonism at hepatocyte growth factor (HGF)/c-Met. The pathway converges on hippocampal synaptic plasticity, neurogenesis, and neuronal survival. Includes Russian-registered Semax and Selank, the multi-country-licensed multi-component cerebrolysin, and the pre-clinical HGF/c-Met potentiator Dihexa.

The cosmetic peptide category is uniquely positioned within this reference: these are the only compounds with fully legal UK regulatory status, sitting under the Cosmetic Products Regulation rather than the medicines framework. Matrixyl (Pal-KTTKS), Argireline (Acetyl Hexapeptide-8), and GHK-Cu are widely used INCI-listed cosmetic ingredients in commercial anti-ageing skincare.

The growth-hormone axis is a neuroendocrine cascade where hypothalamic GHRH and ghrelin drive pulsatile pituitary GH release, with IGF-1 as the principal downstream effector. Synthetic GHRH analogues (sermorelin, CJC-1295, tesamorelin) and GHRP-class ghrelin-receptor agonists (ipamorelin, hexarelin, GHRP-2/6) activate this axis through pharmacologically distinct receptors — the mechanistic basis of the canonical GHRH+GHRP dual-pathway combination.

Gut research peptides span three mechanisms: mucosal angiogenesis and gastric protection (BPC-157), suppression of NF-κB-driven inflammation (KPV), and modulation of intestinal tight junctions (larazotide). Together they cover healing, inflammation, and barrier integrity.

The immune-modulator research peptide class spans T-cell maturation (thymosin alpha-1, thymulin), innate antimicrobial defence (LL-37), and NF-κB-mediated anti-inflammatory pharmacology (KPV). Thymic peptides trace to Goldstein's 1977 bovine Fraction 5 characterisation; thymulin uniquely requires zinc coordination for biological activity.

Joint and cartilage research focuses on compounds that modulate matrix-degrading enzymes (MMP-13, aggrecanases), suppress catabolic cytokines, and support chondrocyte function. Pentosan polysulfate and AOD-9604 are the two best-studied research candidates.

Longevity research peptides span multiple convergent mechanisms addressing the cellular-ageing phenotype: mitochondrial dysfunction (SS-31/elamipretide directly stabilises cardiolipin; humanin and MOTS-c are mitochondrial-derived peptides), telomerase and replicative senescence (epitalon), senolytic clearance of senescent cells (FOXO4-DRI), and the foundational longevity-gene product Klotho whose loss produces dramatic accelerated aging in mice.

The metabolic peptide class spans three mechanistically distinct pharmacological spaces: incretin-pathway GLP-1/GIP/glucagon-receptor agonists (semaglutide, tirzepatide, retatrutide) that dominate contemporary obesity and diabetes treatment; AMPK-pathway compounds (MOTS-c, 5-Amino-1MQ) addressing cellular energy metabolism; and hGH-fragment lipolytic agents (AOD-9604) targeting adipose tissue directly.

Regeneration research peptides operate at the intersection of progenitor-cell biology, cellular senescence, and extracellular-matrix remodelling. Thymosin beta-4 and AC-SDKP are the most-cited examples; epitalon represents the cellular-ageing angle.

Sexual-health research peptides in this category are melanocortin-receptor agonists producing sexual-arousal effects through central nervous system mechanisms — fundamentally distinct from the peripheral vascular mechanism of PDE5 inhibitors. PT-141 (bremelanotide/Vyleesi) is FDA-approved for HSDD in premenopausal women; Melanotan II is the earlier non-selective precursor whose grey-market use has triggered explicit MHRA public warnings.

Skin and wound research is the area where peptide pharmacology has the longest cosmetic and pre-clinical history. GHK-Cu underpins decades of dermal-regeneration work; LL-37 covers antimicrobial defence and re-epithelialisation; BPC-157 contributes angiogenic effects in vascular wound beds.

Tendon and ligament tissue heals slowly and incompletely in clinical practice — a gap that has driven sustained pre-clinical interest in peptides that influence collagen organisation, angiogenesis, and tenocyte migration. The peptides below are the most-studied research compounds in this space.