Peptide Database
265 therapeutic peptides with research summaries, clinical findings, and regulatory status.
BPC-157
A synthetic gastric pentadecapeptide derived from a protein found in human gastric juice. BPC-157 promotes angiogenesis and the expression of growth factors including VEGF, EGF, and NO-mediated pathways. It has demonstrated cytoprotective and wound-healing properties across multiple tissue types in preclinical models, including tendon, muscle, ligament, and gastrointestinal mucosa.
GHK-Cu
A naturally occurring copper-binding tripeptide (glycyl-L-histidyl-L-lysine) found in human plasma, saliva, and urine. GHK-Cu activates tissue remodeling by stimulating collagen synthesis, glycosaminoglycan production, and angiogenesis while suppressing fibrinogen synthesis. It modulates the activity of matrix metalloproteinases and influences over 4,000 genes related to tissue repair.
DSIP (Delta Sleep-Inducing Peptide)
A naturally occurring nonapeptide (Trp-Ala-Gly-Gly-Asp-Ala-Ser-Gly-Glu) originally isolated from cerebral venous blood of rabbits during induced sleep. DSIP modulates sleep architecture by promoting delta wave (slow-wave) sleep through interactions with the GABAergic system and hypothalamic sleep centers. It also exhibits stress-protective, analgesic, and neuromodulatory properties.
P21 (Peptide)
A small synthetic peptide derived from the active region of ciliary neurotrophic factor (CNTF) designed to promote neurogenesis and synaptic plasticity. P21 is a tetrapeptide that crosses the blood-brain barrier and enhances dentate gyrus neurogenesis by increasing BDNF expression. Unlike full-length CNTF, P21 does not activate the JAK-STAT pathway or produce the anorectic and immunogenic effects of the parent protein.
Epithalon (Epitalon)
A synthetic tetrapeptide (Ala-Glu-Asp-Gly) based on the natural epithalamin peptide produced by the pineal gland. Epithalon activates telomerase, the enzyme responsible for maintaining telomere length, thereby potentially extending cellular replicative capacity. It also stimulates melatonin production and modulates neuroendocrine system function associated with aging.
MOTS-c
A mitochondrial-derived peptide encoded by the 12S rRNA gene of mitochondrial DNA. MOTS-c is a 16-amino acid peptide that acts as an exercise mimetic by activating AMPK and regulating metabolic homeostasis. It translocates to the nucleus under metabolic stress to regulate nuclear gene expression related to glucose metabolism and cellular stress responses.
Humanin
A 24-amino acid mitochondrial-derived peptide encoded within the 16S rRNA region of mitochondrial DNA. Humanin exerts cytoprotective and neuroprotective effects by interacting with IGFBP-3, BAX, and the FPRL-1 receptor. It inhibits apoptosis through suppression of the intrinsic mitochondrial death pathway and reduces amyloid-beta-induced neurotoxicity.
FOXO4-DRI
A D-retro-inverso peptide designed to disrupt the interaction between FOXO4 and p53 in senescent cells. In senescent cells, FOXO4 sequesters p53 away from mitochondria, preventing p53-mediated apoptosis and enabling senescent cell survival. FOXO4-DRI competitively binds p53, releasing it to trigger selective apoptosis of senescent cells while sparing healthy cells, functioning as a senolytic agent.
LL-37
The only human cathelicidin antimicrobial peptide, a 37-amino acid cationic peptide cleaved from the precursor protein hCAP18. LL-37 disrupts microbial membranes through electrostatic interactions and exerts broad-spectrum activity against bacteria, fungi, and enveloped viruses. Beyond direct antimicrobial effects, it modulates innate immunity by recruiting immune cells, promoting angiogenesis, and regulating inflammatory cytokine release.
Thymulin
A zinc-containing nonapeptide (facteur thymique serique) produced exclusively by thymic epithelial cells. Thymulin requires zinc for biological activity and promotes T-lymphocyte differentiation, maturation, and function. Circulating thymulin levels decline progressively with age in parallel with thymic involution, and zinc deficiency independently impairs thymulin activity, linking nutritional status to immune competence.
KPV
A C-terminal tripeptide fragment (Lys-Pro-Val) of alpha-melanocyte-stimulating hormone (alpha-MSH) that retains potent anti-inflammatory activity without melanogenic effects. KPV inhibits NF-kB nuclear translocation and reduces production of pro-inflammatory cytokines including TNF-alpha, IL-1beta, and IL-6. It penetrates cell membranes and directly interacts with inflammatory signaling cascades, making it effective topically and orally for mucosal inflammation.
Melanotan II
A synthetic cyclic analog of alpha-melanocyte stimulating hormone (alpha-MSH) that non-selectively activates melanocortin receptors MC1R through MC5R. Melanotan II stimulates melanogenesis for skin tanning via MC1R, modulates sexual arousal through MC3R/MC4R in the hypothalamus, and reduces appetite through central MC4R activation. It is not FDA-approved and carries significant safety concerns.
Palmitoylethanolamide (PEA)
An endogenous fatty acid amide belonging to the N-acylethanolamine family, naturally produced by cells in response to tissue damage and inflammation. PEA acts primarily through peroxisome proliferator-activated receptor alpha (PPAR-alpha), downregulating mast cell activation and pro-inflammatory mediator release. It also modulates the endocannabinoid system via the entourage effect, enhancing anandamide activity at CB1/CB2 receptors and TRPV1 channels without directly binding cannabinoid receptors.
Mod GRF 1-29 (CJC-1295 no DAC)
Modified GRF 1-29 is a synthetic analogue of growth hormone releasing hormone (GHRH) comprising 29 amino acids with four amino acid substitutions to enhance stability. These modifications increase resistance to enzymatic degradation compared to native GHRH while maintaining receptor affinity and biological activity. The compound stimulates pulsatile growth hormone release from the anterior pituitary without the half-life extension conferred by drug affinity complex technology.
Ghrelin (Native)
Ghrelin is a naturally occurring 28-amino acid peptide hormone produced primarily in the stomach with an essential octanoyl modification at serine-3 required for biological activity. It functions as the endogenous ligand for the growth hormone secretagogue receptor (GHS-R1a), stimulating growth hormone release, appetite, and gastric motility. Ghrelin plays a central role in energy homeostasis, feeding behavior, and metabolic regulation.
Obestatin
Obestatin is a 23-amino acid peptide hormone derived from post-translational processing of the ghrelin gene product preproghrelin. It was initially proposed to oppose ghrelin's orexigenic effects by binding to the GPR39 receptor and promoting satiety, though this mechanism remains controversial. The peptide has been investigated for potential roles in regulating food intake, gastrointestinal motility, and metabolic homeostasis.
GHRP-1
Growth Hormone Releasing Peptide-1 is a synthetic hexapeptide belonging to the growth hormone secretagogue family. It acts as a weak agonist at the ghrelin receptor (GHS-R1a) to stimulate pulsatile growth hormone release from the anterior pituitary. GHRP-1 has limited potency compared to later-generation secretagogues and served primarily as a prototype for subsequent drug development.
Pentadeca Arginate (PDA)
Pentadeca Arginate is a synthetic 15-arginine polypeptide designed to enhance cellular uptake and delivery of therapeutic molecules. The polyarginine structure confers cell-penetrating properties by interacting with negatively charged cell membrane components. It has been explored as a carrier for facilitating intracellular delivery of bioactive compounds and as a potential modulator of tissue repair processes.
Thymosin Beta-4 Fragment (TB4-Frag)
Thymosin Beta-4 Fragment refers to bioactive segments derived from the 43-amino acid thymosin beta-4 protein, most commonly a 7-amino acid N-terminal sequence (Ac-SDKP). These fragments retain specific biological activities of the parent peptide, including modulation of actin polymerization, angiogenesis, and inflammation. Shorter fragments may offer improved stability and targeted activity compared to full-length thymosin beta-4.
Cathelicidin LL-37 Fragments
Cathelicidin LL-37 fragments are truncated sequences derived from the human antimicrobial peptide LL-37, which is a 37-amino acid cleavage product of the cathelicidin precursor hCAP18. These fragments retain antimicrobial, immunomodulatory, and wound healing properties while potentially offering improved stability or reduced cytotoxicity. Specific fragments have been designed to preserve angiogenic and chemotactic activities relevant to tissue repair.
FGL Peptide
FGL peptide is a 15-amino acid synthetic sequence derived from the neural cell adhesion molecule (NCAM) that mimics the fibronectin-like domain. It promotes neurite outgrowth and synaptic plasticity by engaging NCAM and fibroblast growth factor receptors without requiring direct cell-cell adhesion. The peptide has been investigated for neuroprotective and cognitive-enhancing properties in models of neurological injury and disease.
Matrikine Peptides
Matrikine peptides are bioactive fragments released from extracellular matrix proteins during tissue remodeling or injury. These sequences, derived from collagen, elastin, fibronectin, and laminin, regulate cellular processes including migration, proliferation, and differentiation by binding to cell surface receptors. Matrikines serve as endogenous signals coordinating wound healing and tissue homeostasis.
Body Protection Compound (BPC) Variants
BPC variants are synthetic peptide sequences related to a pentadecapeptide derived from human gastric juice, commonly designated BPC-157. These peptides are proposed to exhibit gastroprotective, angiogenic, and tissue repair properties through mechanisms that may involve nitric oxide pathways, growth factor modulation, and VEGF receptor interactions. The exact structure-activity relationships and receptor targets remain incompletely defined.
Collagen Tripeptide F (CTP-F)
Collagen Tripeptide F is a synthetic tripeptide designed to mimic fragments of native collagen that appear during tissue remodeling. It is hypothesized to bind to fibroblast surface receptors and promote extracellular matrix deposition, thereby accelerating wound healing and connective tissue repair. The tripeptide structure is intended to enhance bioavailability compared to larger collagen molecules.
Dihexa
Dihexa is a small synthetic hexapeptide derived from angiotensin IV, designed to bind and potentiate hepatocyte growth factor (HGF) signaling through the c-Met receptor. This action is hypothesized to promote synaptogenesis, dendritic spine formation, and neuronal survival in models of cognitive impairment. Dihexa exhibits high oral bioavailability and blood-brain barrier penetration due to its small size and lipophilic character.
Spadin
Spadin is a 17-amino acid peptide derived from the propeptide released during maturation of sortilin, a neurotensin receptor. It functions as an antagonist of the TREK-1 potassium channel, which is implicated in the pathophysiology of major depressive disorder. By blocking TREK-1, spadin increases neuronal excitability and promotes hippocampal neurogenesis, providing a novel antidepressant mechanism distinct from monoaminergic pathways.
Bromantane-adjacent Peptides
Bromantane-adjacent peptides refer to a theoretical class of compounds that may share structural or functional motifs with bromantane, a synthetic adaptogen that influences dopamine synthesis and has mild psychostimulant properties. While bromantane itself is not a peptide, peptide analogs designed to mimic its dopaminergic or anti-asthenic effects are an area of early exploration. Such peptides would aim to enhance cognitive performance and reduce fatigue through modulation of catecholamine pathways.
Orexin A
Orexin A is a 33-amino acid neuropeptide produced in the lateral hypothalamus that plays a critical role in the regulation of wakefulness, arousal, and energy homeostasis. It binds with high affinity to both orexin receptor 1 (OX1R) and orexin receptor 2 (OX2R), promoting cortical activation and stabilizing the wake state. Deficiency of orexin signaling is the hallmark of narcolepsy type 1, making orexin replacement a rational therapeutic strategy.
Orexin B
Orexin B is a 28-amino acid neuropeptide closely related to orexin A, also synthesized in hypothalamic neurons and involved in promoting wakefulness and regulating feeding behavior. It exhibits preferential binding to orexin receptor 2 (OX2R) compared to OX1R. Orexin B contributes to the maintenance of arousal and the integration of metabolic and circadian signals.
Neurotensin
Neurotensin is a 13-amino acid neuropeptide widely distributed in the central nervous system and gastrointestinal tract, where it modulates dopaminergic neurotransmission, nociception, and intestinal function. It acts primarily through the neurotensin receptor 1 (NTSR1), influencing mesolimbic and nigrostriatal pathways implicated in motivation, reward, and motor control. Neurotensin has been studied for its potential roles in schizophrenia, pain modulation, and cognitive function.
Galanin
Galanin is a 29 or 30 amino acid neuropeptide widely distributed throughout the central and peripheral nervous systems. It acts through three G protein-coupled receptor subtypes (GAL1, GAL2, and GAL3) to modulate neurotransmission, particularly in cholinergic, serotonergic, and noradrenergic pathways. The peptide has been implicated in cognitive processes, mood regulation, feeding behavior, and neuroprotection, making it a target of interest for neurodegenerative and psychiatric conditions.
Biopeptide CL (Palmitoyl Tripeptide-5)
Palmitoyl Tripeptide-5 is a synthetic lipopeptide consisting of a tripeptide sequence conjugated to palmitic acid to enhance dermal penetration. The peptide is designed to stimulate collagen synthesis by mimicking the activity of thrombospondin-1, a matricellular protein involved in extracellular matrix remodeling. Its therapeutic rationale centers on attenuating photoaging and improving skin elasticity through upregulation of Types I and III collagen in dermal fibroblasts.
Decorinyl (Tripeptide-10 Citrulline)
Decorinyl is a modified tripeptide featuring citrulline substitution, engineered to interact with decorin, a small leucine-rich proteoglycan that regulates collagen fibrillogenesis. The peptide is proposed to enhance decorin production and activity in the dermis, thereby promoting organized collagen assembly and tensile strength. Its development targets improvement of dermal structural integrity in aging and photoaged skin.
Haloxyl (Chrysin + Palmitoyl Peptides)
Haloxyl is a combination ingredient consisting of chrysin, a naturally occurring flavone, and palmitoyl oligopeptides designed to address periorbital hyperpigmentation and edema. The chrysin component is thought to activate enzyme systems involved in bilirubin and hemoglobin clearance, while the palmitoyl peptides enhance dermal penetration and stimulate lymphatic drainage. This dual-mechanism approach targets the appearance of dark circles attributable to both vascular congestion and iron deposition.
Eyeseryl (Acetyl Tetrapeptide-5)
Acetyl Tetrapeptide-5 is a synthetic tetrapeptide modified with an acetyl group to improve stability and cellular uptake. The peptide is proposed to reduce periorbital edema by modulating capillary permeability and enhancing lymphatic drainage, potentially through downregulation of pro-inflammatory cytokines such as interleukin-1. Its application is focused on reduction of under-eye puffiness and fluid accumulation.
Trylagen (Tripeptide-10 Complex)
Trylagen is a proprietary complex incorporating Tripeptide-10 Citrulline along with additional bioactive peptides formulated to support collagen and elastin network architecture. The complex aims to influence multiple stages of extracellular matrix synthesis and assembly, including fibroblast proliferation, procollagen processing, and elastin fiber organization. The therapeutic rationale is directed toward comprehensive photoaging correction and improvement of skin firmness.
Myristoyl Pentapeptide-17
Myristoyl Pentapeptide-17 is a lipopeptide composed of a pentapeptide sequence conjugated to myristic acid to facilitate penetration of the hair follicle and dermal layers. It is marketed primarily for enhancement of eyelash and eyebrow growth through proposed stimulation of keratin gene expression and prolongation of the anagen phase of the hair cycle. The peptide is intended for cosmetic applications related to hair conditioning and growth.
Palmitoyl Tripeptide-1
Palmitoyl Tripeptide-1 is a synthetic lipopeptide comprising a tripeptide linked to palmitic acid, designed to mimic a portion of the Type I collagen molecule. By binding to fibroblast receptors, it is hypothesized to trigger signaling cascades that upregulate collagen and glycosaminoglycan synthesis. This peptide is widely incorporated into topical anti-aging formulations to promote dermal matrix regeneration and reduce the appearance of fine lines.
Copper Peptide (Prezatide Copper Acetate)
Prezatide Copper Acetate is a tripeptide-copper complex, most commonly represented by the sequence Gly-His-Lys bound to a copper ion. Copper peptides are proposed to enhance wound healing, collagen synthesis, and angiogenesis through modulation of matrix metalloproteinases and growth factor activity. The copper moiety is thought to play a critical role in stabilizing the peptide and serving as a cofactor for lysyl oxidase, an enzyme essential for collagen and elastin cross-linking.
Melitane (Acetyl Hexapeptide-1)
Acetyl Hexapeptide-1 is a synthetic hexapeptide designed to stimulate melanin synthesis by acting as an agonist at melanocortin-1 receptors on melanocytes. The acetyl modification is intended to improve peptide stability and cellular permeability. Its therapeutic rationale is to promote tanning and photoprotection through increased melanogenesis, potentially offering a biomimetic alternative to UV exposure for pigmentation enhancement.
Splenopentin
Splenopentin is a synthetic pentapeptide (Arg-Lys-Glu-Val-Tyr) corresponding to residues 32 to 36 of the splenic hormone splenin. It modulates immune cell function by enhancing macrophage activity and stimulating antibody production. The therapeutic rationale is to provide targeted immune enhancement without whole-organ extract variability.
Bursin
Bursin is a tripeptide (Lys-His-Gly) originally isolated from the bursa of Fabricius in avian species. It promotes B-lymphocyte differentiation and immunoglobulin production. The therapeutic rationale is to selectively enhance humoral immunity in conditions marked by antibody deficiency.
Alpha-MSH
Alpha-melanocyte-stimulating hormone (alpha-MSH) is a 13-amino-acid peptide derived from proopiomelanocortin (POMC). It acts via melanocortin receptors to exert potent anti-inflammatory and immunomodulatory effects, including suppression of proinflammatory cytokines and inhibition of nuclear factor kappa B (NF-kB). Therapeutic interest spans inflammatory and autoimmune disorders.
Beta-Defensin 2
Beta-defensin 2 (hBD-2) is an antimicrobial peptide of approximately 40 amino acids produced by epithelial cells in response to infection or inflammation. It disrupts microbial membranes and also functions as a chemoattractant for immune cells via CCR6 receptor binding. Therapeutic interest includes infection control and immune adjuvant applications.
Beta-Defensin 3
Beta-defensin 3 (hBD-3) is an antimicrobial peptide of approximately 45 amino acids with potent activity against a wide range of pathogens, including antibiotic-resistant strains. It acts by permeabilizing microbial membranes and modulating host immune responses. Therapeutic applications include topical antimicrobial therapy and vaccine adjuvants.
Granulysin
Granulysin is a 15-kDa antimicrobial and cytolytic protein expressed by cytotoxic T lymphocytes and natural killer cells. It disrupts microbial and tumor cell membranes via lipid interactions and induces apoptosis. The therapeutic rationale includes treatment of intracellular infections and cancer immunotherapy.
Atrial Natriuretic Peptide (ANP)
Atrial natriuretic peptide is a 28-amino acid endogenous hormone secreted primarily by atrial cardiomyocytes in response to atrial stretch and volume expansion. It binds to natriuretic peptide receptor A, activating guanylyl cyclase to produce cyclic GMP, which mediates vasodilation, natriuresis, and inhibition of aldosterone and renin secretion. ANP plays a critical role in cardiovascular homeostasis and blood pressure regulation.
C-type Natriuretic Peptide (CNP)
C-type natriuretic peptide is a 22-amino acid member of the natriuretic peptide family that selectively activates natriuretic peptide receptor B (NPR-B). Unlike ANP and BNP, CNP is produced primarily in vascular endothelium and functions as a paracrine regulator of vascular tone and endothelial permeability with minimal direct renal effects. CNP also plays important roles in bone growth and chondrocyte proliferation through cyclic GMP signaling.
Urocortin 2
Urocortin 2 is a 38-amino acid peptide member of the corticotropin-releasing factor family with selective affinity for CRF receptor 2. It exerts cardiovascular effects including coronary and peripheral vasodilation, increased cardiac contractility, and protection against ischemia-reperfusion injury through receptor-mediated cyclic AMP signaling. The selective receptor profile distinguishes it from urocortin 1 and may offer advantages in minimizing stress-axis activation.
Urocortin 3
Urocortin 3, also known as stresscopin, is a 38-amino acid peptide with high selectivity for CRF receptor 2. It produces vasodilation and increases cardiac contractility while exhibiting cardioprotective effects in models of cardiac stress and injury. The selective CRF2 receptor activation avoids hypothalamic-pituitary-adrenal axis stimulation, potentially offering a favorable profile for cardiovascular therapeutics.
Apelin-13
Apelin-13 is a 13-amino acid endogenous peptide that represents the most potent and abundant isoform of the apelin family. It acts as the ligand for the APJ receptor (also known as the apelin receptor), a G protein-coupled receptor expressed in vascular endothelium, cardiomyocytes, and other tissues. The peptide induces vasodilation, enhances cardiac contractility, and modulates fluid homeostasis, providing therapeutic rationale for heart failure and pulmonary hypertension. Its structure consists of a highly conserved C-terminal sequence critical for receptor binding and biological activity.
Glucagon Receptor Antagonist Peptides
Glucagon receptor antagonist peptides are a class of molecules designed to block the glucagon receptor and prevent glucagon-mediated hepatic glucose output. These peptides typically consist of modified glucagon analogs with substitutions that convert agonist activity to antagonism. The therapeutic rationale focuses on lowering blood glucose in type 2 diabetes by reducing hepatic gluconeogenesis and glycogenolysis. Structural modifications also enhance metabolic stability and receptor selectivity.
Motilin
Motilin is a 22-amino acid endogenous peptide hormone secreted by enteroendocrine cells in the duodenum and jejunum. It binds to motilin receptors on gastrointestinal smooth muscle and enteric neurons, stimulating phase III migrating motor complexes and promoting gastric emptying. The therapeutic rationale for exogenous motilin or receptor agonists includes treatment of gastroparesis and postoperative ileus. Erythromycin acts as a motilin receptor agonist, demonstrating the clinical relevance of this pathway.
Gastrin
Gastrin is an endogenous peptide hormone secreted by G-cells in the gastric antrum and duodenum, existing primarily as gastrin-17 and gastrin-34. It binds to the CCK-2 receptor on parietal and enterochromaffin-like cells, stimulating gastric acid secretion and promoting gastric mucosal growth. Therapeutic applications have focused on gastrin analogs for diagnostic purposes and investigation of gastrin immunotherapy for gastrin-dependent tumors. Dysregulation of gastrin secretion occurs in conditions such as Zollinger-Ellison syndrome and atrophic gastritis.
Guanylin
Guanylin is a 15-amino acid endogenous peptide hormone that activates guanylate cyclase-C (GC-C) receptors on intestinal epithelial cells. Upon binding, it stimulates intracellular cyclic GMP production, which regulates chloride and bicarbonate secretion into the intestinal lumen and promotes fluid secretion. This mechanism enhances intestinal motility and fluid balance. Guanylin functions as a paracrine regulator of intestinal homeostasis and salt-water equilibrium.
Dynorphin A
Dynorphin A is an endogenous opioid peptide of 17 amino acids that preferentially binds to and activates kappa-opioid receptors, though it also has affinity for mu and delta receptors at higher concentrations. It is derived from the precursor protein prodynorphin and plays a complex role in pain modulation, stress responses, and dysphoria. Unlike mu-opioid agonists, kappa receptor activation can produce analgesia without typical euphoria but may induce aversive psychological effects. Dynorphin also has non-opioid actions at high concentrations, including NMDA receptor modulation.
Leu-Enkephalin
Leu-enkephalin is a pentapeptide (Tyr-Gly-Gly-Phe-Leu) that functions as an endogenous opioid agonist with preferential activity at delta-opioid receptors and moderate affinity for mu receptors. It is derived from the precursor proenkephalin and is widely distributed in the central and peripheral nervous systems. The peptide modulates nociceptive transmission and contributes to endogenous analgesia. Leu-enkephalin is rapidly degraded by peptidases, limiting its duration of action.
Met-Enkephalin
Met-enkephalin is a pentapeptide (Tyr-Gly-Gly-Phe-Met) that differs from leu-enkephalin only in its C-terminal amino acid. It acts as an endogenous opioid with preferential delta-opioid receptor activity and also binds mu-opioid receptors. Derived from proenkephalin, met-enkephalin is involved in pain modulation, stress responses, and immune regulation. Like other enkephalins, it is subject to rapid enzymatic degradation by aminopeptidases and enkephalinases.
Endomorphin-1
Endomorphin-1 is a tetrapeptide (Tyr-Pro-Trp-Phe) that exhibits highly selective agonist activity at the mu-opioid receptor, the primary target for analgesic opioids. It is one of two endomorphin isoforms and represents the most selective endogenous mu-opioid ligand identified to date. Endomorphin-1 is distributed in pain-processing regions of the central nervous system. Its selective mu receptor activity theoretically offers potent analgesia with a potentially different side effect profile compared to less selective opioids.
Endomorphin-2
Endomorphin-2 is a tetrapeptide (Tyr-Pro-Phe-Phe) that, like endomorphin-1, demonstrates highly selective agonism at mu-opioid receptors. The two endomorphins differ by a single amino acid but share similar receptor selectivity and analgesic properties. Endomorphin-2 is found in spinal and supraspinal sites involved in nociception. Its unique selectivity profile has generated interest in developing analogs that retain efficacy while minimizing respiratory depression and other opioid side effects.
Nociceptin / Orphanin FQ
Nociceptin, also known as orphanin FQ, is a 17-amino acid peptide that acts as the endogenous ligand for the nociceptin/orphanin FQ peptide (NOP) receptor, a member of the opioid receptor family with distinct pharmacology. Despite structural similarity to dynorphin A, nociceptin does not bind classical opioid receptors. Its effects on pain are complex and context-dependent, producing analgesia at the spinal level but pronociceptive or hyperalgesic effects at supraspinal sites. The peptide also modulates stress, anxiety, and reward pathways.
Dermorphin
Dermorphin is a heptapeptide opioid agonist originally isolated from the skin of South American Phyllomedusa frogs. It exhibits high selectivity and affinity for the mu-opioid receptor, with potency approximately 30 to 40 times greater than morphine in animal models. The unique D-alanine residue at position 2 confers resistance to peptidase degradation and contributes to its prolonged analgesic activity. Its potent receptor binding has made it a valuable research tool for studying opioid receptor pharmacology.
Deltorphin
Deltorphin is a heptapeptide opioid agonist also derived from Phyllomedusa frog skin secretions, characterized by high selectivity for delta-opioid receptors. Like dermorphin, it contains an unusual D-amino acid residue that enhances metabolic stability and receptor affinity. Deltorphin exhibits analgesic properties distinct from mu-opioid agonists, with reduced respiratory depression and addiction liability in animal models. It has served as a pharmacological tool to elucidate delta-opioid receptor physiology and potential therapeutic roles.
Neuropeptide FF
Neuropeptide FF (NPFF) is an octapeptide belonging to the RFamide family, characterized by an arginine-phenylalanine-amide motif at the C-terminus. It acts on two G protein-coupled receptors, NPFF1 and NPFF2, and modulates opioid-induced analgesia, tolerance, and hyperalgesia. NPFF is widely distributed in the central nervous system and participates in pain modulation, opioid tolerance mechanisms, and cardiovascular regulation. Its dual role as both a pronociceptive and anti-opioid peptide has generated interest in targeting its receptors for chronic pain management.
Magainin 2
Magainin 2 is a 23-amino acid antimicrobial peptide originally isolated from the skin of the African clawed frog Xenopus laevis. It exerts broad-spectrum antimicrobial activity through membrane disruption, forming pores in bacterial membranes while exhibiting relative selectivity over mammalian cells. Magainin 2 belongs to the alpha-helical cationic antimicrobial peptide family and has served as a template for numerous synthetic analogs. Its mechanism of action, which is distinct from conventional antibiotics, offers potential against multidrug-resistant pathogens.
Defensin HNP-1
Human neutrophil peptide 1 (HNP-1) is a 30-amino acid alpha-defensin produced by neutrophils as part of the innate immune response. It contains three stabilizing disulfide bonds and forms amphipathic structures that disrupt microbial membranes through electrostatic and hydrophobic interactions. HNP-1 exhibits antimicrobial activity against bacteria, fungi, and enveloped viruses, and also modulates immune cell function and inflammatory responses. As an endogenous peptide, it has been studied for potential therapeutic augmentation in immunocompromised states and chronic infections.
Alpha-Defensin 5
Alpha-defensin 5 (HD5) is a 32-amino acid cationic peptide predominantly expressed by Paneth cells in the small intestinal crypts. It contains three disulfide bonds that stabilize its beta-sheet structure and enable membrane disruption of bacteria, fungi, and some viruses. HD5 plays a critical role in maintaining intestinal homeostasis by regulating gut microbiota composition and protecting the epithelial barrier. Altered HD5 expression has been implicated in inflammatory bowel disease, necrotizing enterocolitis, and susceptibility to enteric infections.
Indolicidin
Indolicidin is a 13-amino acid antimicrobial peptide derived from bovine neutrophils, characterized by a high tryptophan content (five residues). It exerts antimicrobial activity through multiple mechanisms, including membrane disruption, DNA binding, and inhibition of intracellular processes. The peptide adopts an extended wedge-shaped conformation that facilitates insertion into lipid bilayers. Indolicidin demonstrates activity against bacteria, fungi, and certain protozoa, though its clinical development has been limited by cytotoxicity.
Osteogenic Growth Peptide (OGP)
Osteogenic Growth Peptide is a naturally occurring 14-amino acid peptide identified in serum that promotes osteoblast proliferation and differentiation. The peptide activates the MAP kinase signaling pathway and stimulates collagen synthesis in bone-forming cells. OGP also demonstrates hematopoietic activity, influencing stem cell differentiation in the bone marrow microenvironment. Synthetic analogs have been developed to enhance stability and receptor affinity for potential therapeutic applications in osteoporosis and fracture healing.
Calcitonin Gene-Related Peptide (CGRP)
Calcitonin gene-related peptide is a 37-amino acid neuropeptide produced by alternative splicing of the calcitonin gene. CGRP acts as a potent vasodilator and plays a key role in migraine pathophysiology by binding to CGRP receptors on vascular smooth muscle and trigeminal nerve endings. While CGRP itself has effects on bone metabolism through regulation of osteoblast and osteoclast activity, therapeutic development has focused primarily on antagonizing CGRP signaling rather than administering the peptide. The peptide's role in bone includes modulation of bone formation and vascular coupling in skeletal tissue.
Klotho Peptide
Klotho is a transmembrane protein of approximately 1012 amino acids that exists in membrane-bound and secreted forms, with the soluble ectodomain functioning as a circulating factor. Klotho acts as a coreceptor for fibroblast growth factor 23 in phosphate metabolism and independently influences insulin signaling, oxidative stress, and cellular senescence pathways. Reduced klotho expression is associated with accelerated aging phenotypes in mice, while overexpression extends lifespan in rodent models. Therapeutic development focuses on peptide fragments or recombinant forms to replicate klotho's protective effects in age-related conditions.
Sirtuin-Activating Peptides
Sirtuin-activating peptides represent a class of investigational compounds designed to enhance the enzymatic activity of sirtuins, a family of NAD-dependent deacetylases implicated in longevity and metabolic regulation. These peptides aim to mimic or potentiate the effects of caloric restriction by modulating histone deacetylation, mitochondrial biogenesis, and stress resistance pathways. While small molecule sirtuin activators such as resveratrol analogues have received more research attention, peptide-based approaches remain in early discovery phases. The therapeutic rationale centers on reproducing the lifespan-extending effects of sirtuin overexpression observed in lower organisms.
IGF-1 LR3 (Long-Arg3)
IGF-1 LR3 is a synthetic analogue of insulin-like growth factor 1 with an N-terminal extension of 13 amino acids and a substitution of arginine for glutamic acid at position 3. These modifications reduce binding to IGF-binding proteins, resulting in an extended half-life and increased bioavailability compared to native IGF-1. The peptide promotes anabolic processes including muscle protein synthesis, glucose uptake, and cellular proliferation. IGF-1 LR3 is not approved for human use and is primarily available as a research reagent, though it is sometimes misused in athletic and bodybuilding contexts.
IGF-1 DES (1-3)
IGF-1 DES (1-3) is a truncated analogue of insulin-like growth factor 1 lacking the first three N-terminal amino acids (glycine-proline-glutamate). This structural modification prevents binding to IGF binding proteins in serum, resulting in a shorter half-life but significantly increased potency at the IGF-1 receptor compared to native IGF-1. The peptide is hypothesized to promote localized muscle hypertrophy and tissue repair through enhanced receptor activation in target tissues.
MGF (Mechano Growth Factor)
Mechano Growth Factor is a splice variant of the IGF-1 gene expressed in response to mechanical stress on muscle tissue. The peptide contains a unique C-terminal domain resulting from alternative splicing that distinguishes it from systemic IGF-1. MGF is proposed to act locally in skeletal muscle to activate satellite cells and promote muscle fiber repair and hypertrophy following mechanical loading or injury.
PEG-MGF
PEG-MGF is a pegylated derivative of Mechano Growth Factor designed to extend systemic half-life through the addition of polyethylene glycol moieties. Pegylation reduces renal clearance and proteolytic degradation, theoretically allowing for less frequent dosing and broader tissue distribution compared to unmodified MGF. The modified peptide retains the proposed satellite cell activation properties of native MGF.
Follistatin-344
Follistatin-344 is a 344-amino acid glycoprotein that functions as a binding protein and endogenous antagonist of myostatin and other members of the TGF-beta superfamily. By sequestering myostatin, follistatin removes inhibitory signals that limit skeletal muscle growth, thereby permitting increased muscle fiber hypertrophy and hyperplasia. The peptide also modulates activin and bone morphogenetic protein signaling pathways.
Gadopentetate Peptide Conjugates
Gadopentetate peptide conjugates consist of the gadolinium-based contrast agent gadopentetate dimeglumine chemically linked to targeting peptides designed to bind specific tissue markers or receptors. These hybrid molecules combine the MRI contrast properties of chelated gadolinium with the molecular specificity of peptides to enable targeted imaging of tumors, inflammatory lesions, or vascular pathology. Various peptide motifs including RGD sequences and somatostatin analogs have been conjugated to gadolinium chelates for preclinical evaluation.