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Research Library

The science behind every vial.

Mechanism, receptor pharmacology, downstream signaling, and the cited preclinical literature for every compound in the X Factor catalog. Each section pairs the technical breakdown with a plain-language sidebar for quick orientation. Cross-checkable against PubMed and PMC. Strictly research use only — nothing here describes human use, dosing, or therapeutic claims.

8 compounds documented 50+ primary citations Plain-language sidebars RUO context only
Preamble

How to read this library.

Each compound section follows the same structure: Identity — sequence, class, primary research domain. Mechanism — receptor or molecular target, the primary signaling cascade, and the key downstream effectors documented in the literature. Pathway diagram — a simplified inline schematic of the canonical signaling axis. Preclinical evidence — selected primary citations with PubMed or PMC identifiers. Storage and reconstitution context — typical handling per published protocol literature.

Where a citation is referenced in the body, it is also indexed at the bottom under Full reference index with a stable PMID/PMCID/DOI. Researchers are encouraged to verify each claim against the cited source. If you find an error, please email research@xfactorpeptidelab.com.

Nothing here is medical advice. Nothing here describes human dosing, human use, or therapeutic application. All material is intended for in-vitro and non-clinical laboratory research conducted by qualified investigators 21 or older.

Glossary

Terms used on this page.

RUO — Research Use Only

A regulatory designation. Material sold "RUO" is a research reagent — not a food, drug, supplement, or cosmetic. It cannot legally be marketed for human use.

In vitro vs in vivo

"In vitro" = in a dish (cell culture). "In vivo" = in a living organism, typically a rodent in preclinical work. Both are pre-human research.

Receptor / GPCR / RTK

A receptor is a protein on or inside a cell that binds a specific molecule. GPCR = G-protein-coupled receptor (a major class). RTK = receptor tyrosine kinase (another class). Different receptor types use different intracellular signaling.

Signaling cascade

When a receptor is activated, it triggers a chain of internal reactions ("cascade") that ultimately changes gene expression or cell behavior. cAMP/PKA, PI3K/Akt, MAPK/ERK are common cascades.

Pharmacokinetics

How a molecule moves through a system over time — absorption, distribution, metabolism, elimination. "Half-life" is how long it takes for half a dose to clear.

COA — Certificate of Analysis

A document from an independent laboratory verifying a batch's identity (mass spec) and purity (HPLC). Every X Factor batch ships with a per-lot COA.

Lyophilized

Freeze-dried into a stable powder for shipping. Researchers reconstitute lyophilized peptide in bacteriostatic water before use in their experiments.

PMID / PMCID / DOI

Stable identifiers for primary literature. PMID = PubMed ID. PMCID = PubMed Central ID (full text often free). DOI = digital object identifier.

PENTADECAPEPTIDERUO

BPC-157

Body Protection Compound — a synthetic 15-amino-acid sequence derived from a partial sequence of a protein found in human gastric juice. Studied extensively in rodent injury, inflammation, and gastrointestinal models since the early 1990s by Sikiric and colleagues at the University of Zagreb.

Identity
  • Sequence: Gly-Glu-Pro-Pro-Pro-Gly-Lys-Pro-Ala-Asp-Asp-Ala-Gly-Leu-Val (15 aa)
  • Origin: partial sequence of a protein isolated from human gastric juice
  • Stability: reportedly stable in human gastric juice >24h [1]
  • Primary domains: GI cytoprotection · tendon & muscle injury models · vasomotor research

Mechanism of action

Published preclinical literature documents BPC-157 modulating VEGFR2 → Akt → eNOS and Src → Caveolin-1 → eNOS signaling axes, leading to nitric-oxide production, vasodilation, and angiogenesis in cell-culture and rodent models. Hsieh et al. (2020, Scientific Reports) demonstrated that BPC-157 enhances expression and endocytosis of VEGFR2 with subsequent phosphorylation of AKT and eNOS, supporting both VEGF-dependent and VEGF-independent NO pathways [2]. Sikiric and colleagues have published extensively on the NO-system relationship, showing nitric-oxide modulation contributes to BPC-157's healing effect across multiple tissue-injury models [3,4].

Additional preclinical work documents upregulation of growth-factor receptors at injury sites [5], fibroblast and tendon-cell migration via FAK-paxillin signaling [6], and effects on dopaminergic and serotonergic systems in CNS models [4]. A 2025 narrative review in Pharmaceuticals by Józwiak et al. summarizes the multifunctionality and patent landscape [7].

Canonical signaling diagram

BPC-157 VEGFR2 Src · Cav-1 Akt → eNOS NO ↑

Selected preclinical evidence

Storage & reconstitution literature

Lyophilized peptide is typically stored at −20 °C, light-protected. Reconstituted in bacteriostatic water and reported in protocol literature to remain stable refrigerated (2–8 °C) for approximately 30 days under sterile handling. Repeated freeze-thaw cycles are typically avoided.

THYMOSIN-β4 FRAGMENTRUO

TB-500 (Thymosin-β4 active fragment)

Synthetic peptide containing the active actin-binding motif (LKKTETQ) of the 43-amino-acid protein thymosin-β4 — the principal G-actin sequestering molecule in mammalian cells. Studied since the 1980s in cell-migration, wound-healing, and cardiac-injury models.

Identity
  • Active motif: LKKTETQ (within the parent 43-aa Tβ4)
  • Class: intracellular actin-sequestering peptide; β-thymosin family
  • Domains: wound-healing models · cardiac-cell migration · ligament/tendon repair models

Mechanism of action

Thymosin-β4 sequesters monomeric G-actin at a 1:1 stoichiometry through the LKKTETQ motif, regulating the G/F-actin equilibrium and influencing cytoskeletal dynamics, cell migration, and tissue-remodeling processes [9,10]. Beyond actin sequestration, preclinical literature documents activation of integrin-linked kinase (ILK), modulation of NF-κB pathways, and upregulation of VEGF expression in angiogenesis models [11].

Bock-Marquette et al. (2004, Nature) demonstrated that Tβ4 activates ILK and Akt, promoting cardiac cell migration and survival in a rodent myocardial infarction model [11]. Malinda et al. (1999, J Invest Dermatol) reported topical or intraperitoneal Tβ4 increased re-epithelialization by 42% at day 4 and 61% at day 7 versus saline controls in a rat full-thickness wound model [12]. Goldstein et al. (2012) provide a comprehensive mechanistic review [10].

Canonical signaling diagram

TB-500 / Tβ4 G-actin sequester ILK · Akt activation cell migration · angiogenesis · ECM

Selected preclinical evidence

Cu(II) TRIPEPTIDERUO

GHK-Cu

Glycyl-L-histidyl-L-lysine bound to a copper(II) ion. Naturally occurring in human plasma; isolated by Loren Pickart in 1973 while studying age-related differences in tissue-repair activity in human albumin fractions. Extensively studied in dermal-research and ECM-remodeling preclinical models.

Identity
  • Sequence: Gly-L-His-L-Lys (3 aa) · 1:1 Cu(II) complex
  • Origin: isolated from human plasma (Pickart, 1973)
  • Domains: dermal-fibroblast research · ECM remodeling · antioxidant gene expression

Mechanism of action

GHK forms a stable 1:1 complex with Cu(II). The peptide-copper complex modulates expression of a broad set of ECM and antioxidant genes. Pickart and Margolina (2018, Int J Mol Sci) reviewed transcriptomic evidence indicating GHK-Cu modulates a substantial number of human genes, with particular relevance to collagen I/III synthesis, MMP-2/TIMP-1 balance, decorin synthesis, and SOD3 antioxidant expression in cultured fibroblasts [14].

In primary work, GHK-Cu at 0.01–100 nM applied to human adult dermal fibroblasts increased elastin and collagen production, and modulated MMP1/MMP2/TIMP1 in concentration-dependent fashion [15]. Maquart et al. (1988, FEBS Lett) provided the foundational demonstration that the GHK-Cu complex stimulates collagen synthesis in fibroblast cultures [16]. A 2024 review by Park et al. summarizes tripeptide roles in wound healing and skin regeneration [17].

Canonical mechanism diagram

GHK-Cu(II) Cu transport · SOD3 MMP-2 / TIMP-1 collagen I/III · decorin · ECM

Selected preclinical evidence

GHRH(1–29)RUO

Sermorelin

Synthetic 29-amino-acid fragment corresponding to the biologically active N-terminal sequence of growth-hormone-releasing hormone (GHRH 1–29). Widely used as a research tool for studying pituitary somatotrope physiology.

Identity
  • Sequence: 29-aa fragment of native human GHRH(1–44)
  • Receptor: GHRH-R (class-B GPCR), pituitary somatotrope
  • Domain: growth-axis preclinical research, pituitary physiology

Mechanism of action

Sermorelin engages the GHRH receptor — a class-B G-protein-coupled receptor expressed predominantly on pituitary somatotroph cells. Receptor binding activates the canonical class-B cascade Gαs → adenylate cyclase → cAMP → PKA, with phosphorylation of CREB and transcription of growth-hormone messenger RNA [19,20].

Walker (1991, Drugs Aging) characterized sermorelin's preferential pituitary engagement; subsequent work established its use as a pituitary-axis research tool. Because sermorelin engages the natural GHRH receptor in a pulsatile fashion, preclinical literature contrasts its profile with continuous-receptor agonists in receptor-desensitization studies [20].

Selected preclinical evidence

STABILIZED GHRHRUO

Tesamorelin

Trans-3-hexenoyl-modified GHRH(1-44) analog with extended plasma half-life vs native GHRH; engages the same GHRH-R / Gαs / cAMP / PKA pathway at the pituitary somatotrope.

Identity
  • Modification: N-terminal trans-3-hexenoyl group conferring resistance to DPP-4 cleavage
  • Receptor: GHRH-R (class-B GPCR)
  • Domain: pituitary GH-axis research, visceral-adipose preclinical models

Mechanism of action

Tesamorelin engages GHRH-R with the same canonical Gαs / cAMP / PKA cascade as native GHRH. The N-terminal lipid modification confers resistance to dipeptidyl peptidase-4 (DPP-4) cleavage, extending half-life relative to unmodified GHRH analogs [22,23]. Falutz et al. (2007, NEJM) reported visceral-adipose effects in clinical research; Stanley et al. (2012, JCEM) demonstrated that responders showed correlated metabolic-profile changes (triglycerides, adiponectin, glucose homeostasis) [22,23].

Selected literature

TRI-AGONISTINVESTIGATIONALRUO

GLP-3-R (retatrutide-class research analog)

Investigational research analog in the class of triple incretin receptor agonists studied for combined GLP-1, GIP, and glucagon receptor engagement in preclinical metabolic models. The reference compound (LY3437943, retatrutide) is in late-stage Eli Lilly development.

Identity
  • Class: triple GLP-1 / GIP / glucagon receptor agonist research analog
  • Receptors engaged: GLP-1R, GIP-R, GCGR (all class-B GPCRs)
  • Reference molecule: LY3437943 (retatrutide), Coskun et al. Cell Metab 2022

Mechanism of action

All three target receptors signal primarily via Gαs → adenylate cyclase → cAMP → PKA. The triple-agonist profile is reported in preclinical and early clinical work to combine the insulin-secretion and satiety effects of incretin agonism (GLP-1R, GIP-R) with the energy-expenditure effects of glucagon-receptor signaling (GCGR) [25,26]. Coskun et al. (2022, Cell Metab) characterized LY3437943's preclinical pharmacology; Jastreboff et al. (2023, NEJM) reported its Phase 2 obesity data; additional Phase 3 readouts are appearing through 2026 [25,26,27].

Selected literature

RESEARCH BLENDRUO

KLOW Blend

Combination research blend of KPV, GHK-Cu, BPC-157, and TB-500 used by investigators studying convergent tissue-remodeling and inflammation pathways. Each constituent has independent preclinical literature; the blend exists for protocol-level convenience in cell-culture and rodent models where multi-pathway engagement is the experimental aim.

Constituents and their independent mechanisms
  • KPV — α-MSH C-terminal tripeptide (Lys-Pro-Val). Reported anti-inflammatory effects in colitis and dermatologic preclinical models, often described as MC1R-independent [29].
  • GHK-Cu — see §GHK-Cu (copper transport, MMP modulation, ECM remodeling).
  • BPC-157 — see §BPC-157 (VEGFR2 / eNOS, angiogenesis, tissue protection).
  • TB-500 — see §TB-500 (actin sequestration, cell migration, ILK / Akt).

Researchers should reference each constituent's primary literature individually; this product does not have its own combined-product randomized publications. Lot composition and per-constituent concentration are reported on the COA.

Selected KPV literature

RESEARCH BLENDDERMALRUO

GLOW Blend

Combination research blend of GHK-Cu, BPC-157, and TB-500 used in dermal-research and ECM-remodeling preclinical contexts. As with KLOW, each constituent is documented independently; researchers should consult primary literature per constituent.

The three constituents collectively engage copper-dependent ECM remodeling (GHK-Cu — collagen I/III, MMP-2/TIMP-1, decorin), angiogenesis and vasomotor signaling (BPC-157 — VEGFR2 / Akt / eNOS), and cell-migration cytoskeletal dynamics (TB-500 — G-actin sequestration, ILK / Akt). The three pathways converge in dermal-fibroblast and integumentary preclinical models.

No combined-product randomized literature exists for the blend; refer to each constituent section for primary citations.

Reference index

Full citations.

  1. Sikiric P, et al. Novel cytoprotective mediator BPC 157. Curr Pharm Des 24(18):1990-2001 (2018). PMID 29879879.
  2. Hsieh MJ, et al. Modulatory effects of BPC 157 on vasomotor tone & Src-Cav-1-eNOS pathway. Sci Rep 10:17078 (2020). DOI 10.1038/s41598-020-74022-y.
  3. Sikiric P, et al. BPC 157 Robert's stomach cytoprotection. Curr Pharm Des 26(25):2855-2866 (2020). PMCID PMC7096228.
  4. Sikiric P, et al. BPC 157 and the central nervous system. Neural Regen Res 17(3):482-487 (2022). PMCID PMC8504390.
  5. Chang CH, et al. BPC 157 promotes tendon-fibroblast outgrowth. J Appl Physiol (2011). PMID 21030672.
  6. Sikiric P, et al. Stable gastric pentadecapeptide BPC 157 and wound healing. Front Pharmacol 12:627533 (2021). DOI 10.3389/fphar.2021.627533.
  7. Józwiak M, et al. Multifunctionality and possible medical application of BPC 157. Pharmaceuticals 18(2):185 (2025). DOI 10.3390/ph18020185.
  8. Sikiric P, et al. BPC 157 therapy: angiogenesis and NO comment. Pharmaceuticals (2025). PMCID PMC12567428.
  9. Goldstein AL, Hannappel E, Kleinman HK. Tβ4 actin-sequestering protein moonlights to repair injured tissues. Trends Mol Med 11(9):421-9 (2005). PMID 16099219.
  10. Goldstein AL, et al. Tβ4: multifunctional regenerative peptide. Ann NY Acad Sci 1270:1-9 (2012). PMID 23045985.
  11. Bock-Marquette I, et al. Tβ4 activates ILK and promotes cardiac repair. Nature 432:466-472 (2004). PMID 15525989.
  12. Malinda KM, et al. Tβ4 accelerates wound healing. J Invest Dermatol 113(3):364-368 (1999). PMID 10469335.
  13. Smart N, et al. Tβ4 induces adult epicardial progenitor mobilization. Nature (2007). PMID 22214374.
  14. Pickart L, Margolina A. Regenerative actions of GHK-Cu. Int J Mol Sci 19(7):1987 (2018). PMCID PMC6073405.
  15. Pickart L, et al. GHK-Cu in oxidative stress and aging. Biomed Res Int (2015). PMID 26236730.
  16. Maquart FX, et al. Stimulation of collagen synthesis by GHK-Cu. FEBS Lett (1988). PMID 3169239.
  17. Park J, et al. Tripeptides in wound healing — comprehensive review. Int J Med Sci (2024). medsci v22p4175.
  18. Pickart L, Margolina A. GHK as natural modulator in skin regeneration. Biomed Res Int (2015). PMCID PMC4508379.
  19. Walker RF. Sermorelin: a better approach to GH research. Drugs Aging (1991). PMID 1782195.
  20. Walker RF. Sermorelin: a better approach to adult-onset GH insufficiency? Clin Interv Aging 1(4):307-308 (2006). PMCID PMC2699646.
  21. Prakash A, Goa KL. Sermorelin review. BioDrugs (1999). PMID 18031173.
  22. Falutz J, et al. Tesamorelin in HIV. N Engl J Med 357:2359-2370 (2007). DOI 10.1056/NEJMoa072375.
  23. Stanley TL, et al. Visceral adiposity and tesamorelin response. JCEM 97(3):989-998 (2012). PMCID PMC3348954.
  24. Stanley TL, Grinspoon SK. GHRH effects on visceral fat & metabolism. Growth Horm IGF Res (2015). PMID 24005249.
  25. Coskun T, et al. LY3437943 triple GIP/GLP-1/glucagon agonist. Cell Metab 34(9):1234-1247 (2022). PMID 36354040.
  26. Jastreboff AM, et al. Retatrutide Phase 2. N Engl J Med 389:514-526 (2023). DOI 10.1056/NEJMoa2301972.
  27. Urva S, et al. LY3437943 Phase 1b in T2D. Lancet (2022). DOI 10.1016/S0140-6736(22)02033-5.
  28. Triple agonism-based therapies for obesity. Curr Cardiovasc Risk Rep (2025). DOI 10.1007/s12170-025-00770-z.
  29. Mandrika I, et al. α-MSH and KPV inhibit cytokine-induced NF-κB activation. FEBS Lett (2001). PMID 16174943.
Disclaimer

Research-use only.

All material on this page describes published preclinical and in-vitro research. Statements about mechanism, signaling, and pathway are summarized from cited primary sources and reviews. Nothing on this page constitutes medical, dietary, or therapeutic advice. Products are not foods, drugs, supplements, or cosmetics; they are not evaluated by the U.S. Food and Drug Administration; and they are not intended to diagnose, treat, cure, or prevent any disease. Products are intended for in-vitro and non-clinical research conducted by qualified researchers 21 or older.

Where claims are made, citations are provided. Researchers are encouraged to verify each claim against the cited source. Errors or omissions should be reported to research@xfactorpeptidelab.com for correction.