KLOW is not a single peptide. It is a pre-combined blend of four research peptides in one lyophilized vial: GHK-Cu (50 mg), KPV (10 mg), BPC-157 (10 mg) and TB-500 (10 mg), for 80 mg in total. The name is a supplier designation rather than a compound name found in the scientific literature, and no published study has examined the four peptides together.
GLOW, a related blend, contains the same components minus KPV: BPC-157 (10 mg), GHK-Cu (50 mg) and TB-500 (10 mg), 70 mg in total. This article describes each component from primary sources, works out what the labeled masses mean in molar terms, and sets out why a laboratory might, or might not, want a pre-combined vial rather than four separate ones.
What is in a KLOW vial
The compositions below are the ones Anhydrolabs supplies. Masses are as labeled per vial.
| Component | KLOW (80 mg) | GLOW (70 mg) | Share of KLOW by mass |
|---|---|---|---|
| GHK-Cu | 50 mg | 50 mg | 62.5% |
| KPV | 10 mg | — | 12.5% |
| BPC-157 | 10 mg | 10 mg | 12.5% |
| TB-500 | 10 mg | 10 mg | 12.5% |
| Total | 80 mg | 70 mg | 100% |
By this composition, KLOW is the GLOW combination with KPV added. The two blends are otherwise identical, which makes them a natural pair for experiments that need to isolate what the fourth component changes.
The four components
GHK-Cu
GHK is the tripeptide glycyl-L-histidyl-L-lysine (Gly-His-Lys), and GHK-Cu is its complex with copper(II). In a 1980 Nature paper, Pickart and colleagues described GHK as a plasma tripeptide that co-isolated with roughly equimolar copper, showed that it readily forms complexes with copper(II), and reported that it enhanced copper uptake into cultured hepatoma cells. They proposed that it acts as a copper transport factor, noting a resemblance to the copper-binding sites of albumin, where copper is held by a histidine next to a basic residue. A 2018 review by Pickart and Margolina summarizes later gene-expression work on GHK in cultured cells.
GHK-Cu is the largest component of both blends by mass. It has its own full profile: GHK-Cu, the copper peptide. Anhydrolabs also supplies it on its own as GHK-Cu.
KPV
KPV is the tripeptide Lys-Pro-Val. PubChem lists it as alpha-MSH (11–13), meaning it is the C-terminal three residues of alpha-melanocyte-stimulating hormone. In a 2008 study in Gastroenterology, Dalmasso and colleagues reported that KPV is taken up into intestinal epithelial cells and T cells by PepT1, a transporter for di- and tripeptides, and that nanomolar concentrations inhibited NF-κB and MAP kinase signaling activation in Caco2-BBE and HT29-Cl.19A intestinal cells and Jurkat T cells stimulated with pro-inflammatory cytokines. The same paper studied KPV in DSS- and TNBS-induced colitis models in mice. It is available on its own as KPV.
BPC-157
BPC-157 is a 15-residue synthetic peptide, Gly-Glu-Pro-Pro-Pro-Gly-Lys-Pro-Ala-Asp-Asp-Ala-Gly-Leu-Val, described in 1993 as a fragment of a gastric juice protein. No receptor has been identified; cell studies have reported changes in VEGFR2, focal adhesion kinase and growth hormone receptor signaling. The full profile is what is BPC-157.
TB-500
TB-500 is the acetylated heptapeptide Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln, residues 17 to 23 of thymosin beta-4, taken from the part of that protein that binds actin monomers. Anti-doping chemists first characterized it in the literature in 2012 after identifying it in a commercial product. The full profile is what is TB-500, and it is compared with BPC-157 in BPC-157 vs TB-500.
Identity of each component
Values are from PubChem. For GHK-Cu, PubChem holds several records for different copper complexes; the table uses the 1:1 complex, prezatide copper, and lists free GHK alongside it.
| Component | Sequence | Formula | Molecular weight | CAS | PubChem CID |
|---|---|---|---|---|---|
| GHK (free peptide) | Gly-His-Lys | C14H24N6O4 | 340.38 g/mol | 49557-75-7 | 73587 |
| GHK-Cu (1:1 complex, prezatide copper) | Gly-His-Lys · Cu(II) | C14H23CuN6O4+ | 402.92 g/mol | 89030-95-5 | 71587328 |
| KPV | Lys-Pro-Val | C16H30N4O4 | 342.43 g/mol | 67727-97-3 | 125672 |
| BPC-157 | GEPPPGKPADDAGLV | C62H98N16O22 | 1419.5 g/mol | 137525-51-0 | 9941957 |
| TB-500 | Ac-LKKTETQ | C38H68N10O14 | 889.0 g/mol | 885340-08-9 | 62707662 |
What the masses mean in moles
Blend labels are written in milligrams, but cells respond to molar concentrations, and these four molecules differ in size by a factor of about four. Dividing each labeled mass by its molecular weight gives the amount of each peptide in one vial:
| Component | Mass | Approximate amount | Share of KLOW by moles | Share of GLOW by moles |
|---|---|---|---|---|
| GHK-Cu | 50 mg | 124.1 µmol | 72.3% | 87.2% |
| KPV | 10 mg | 29.2 µmol | 17.0% | — |
| TB-500 | 10 mg | 11.25 µmol | 6.6% | 7.9% |
| BPC-157 | 10 mg | 7.04 µmol | 4.1% | 4.9% |
Two things stand out. GHK-Cu dominates both blends: roughly 18 molecules of it for every molecule of BPC-157. And the three components labeled at 10 mg are far from equimolar, because KPV is about a quarter the size of BPC-157. Anyone designing an experiment around a blend needs this table, not the milligram figures.
These are nominal figures. They assume the labeled mass is peptide (or, for GHK-Cu, the 1:1 copper complex) rather than a salt with counter-ions and residual water, which is why the certificate for the lot, not the label, should be the basis for any calculation.
Why a lab might choose a pre-combined blend
A blend is a convenience with trade-offs. The reasons a laboratory might use one:
- A fixed, reproducible ratio. If an experiment always uses these four components at this ratio, one vial removes four separate weighings and the error that each one adds.
- One lot, one certificate. All components in a vial share a lot number and are characterized together, which simplifies record-keeping across a series of experiments. For longer series, Anhydrolabs also supplies both blends as 10-vial kits from a single lot.
- Paired comparisons. Because KLOW and GLOW differ by exactly one component, running them side by side is a direct way to ask what KPV adds to the other three under identical conditions.
And the reasons it may not suit:
- The ratio cannot be changed. A concentration series for one component moves all four together.
- Single-component controls need separate vials. A design that asks what each peptide contributes needs the individual compounds, such as BPC-157, TB-500, GHK-Cu and KPV, alongside the blend.
- Interactions are unstudied. No published work characterizes these four peptides in one solution. Copper(II) is held by GHK, but whether any of it exchanges onto the other peptides in a mixed solution has not been reported, so the blend should be treated as its own test article, not as the sum of four known ones.
Testing a four-component blend
Analytically, a blend is harder than a single peptide, and the certificate should reflect that.
- Per-component identity. Mass spectrometry should confirm each of the four components separately. Their masses are well spread, from GHK at about 340 Da to BPC-157 at about 1419 Da, so they are straightforward to tell apart.
- Per-component purity and content. A single purity figure for the whole vial says little. Reversed-phase HPLC can report each component's purity as the area of the principal peak for that component relative to its related impurities, and a quantitative method is needed to confirm that each is present at its labeled amount.
- Copper. For GHK-Cu, the copper content is part of identity. A certificate may report it, or the copper complex may be confirmed by mass spectrometry.
What a complete certificate should contain, and how to read one, is covered in how to read a peptide certificate of analysis.
Handling
Anhydrolabs supplies KLOW and GLOW as lyophilized powders in vacuum-sealed vials. The general rules for dry peptides apply: keep sealed vials frozen, dry and protected from light, and let a cold vial reach room temperature before opening. All four components are water-soluble short peptides or peptide complexes, and aqueous buffers are the usual solvent for in-vitro stocks. Because the blend is dominated by GHK-Cu, buffer components that chelate copper strongly, such as EDTA, could strip copper from the complex, and are worth avoiding unless that is the intent. Divide stocks into single-use aliquots. Temperatures and details are in the storage and handling guide.
Regulatory status
None of the four components is an approved drug in the United States, and neither blend is an approved product. On FDA's Category 2 page for compounding, updated April 22, 2026, BPC-157, TB-500, KPV and GHK-Cu (in an entry limited to certain routes) all appear among nominations withdrawn by the nominators. FDA presented BPC-157, KPV and TB-500 to its compounding advisory committee (PCAC) on July 23, 2026, and proposed that none of them, in free base or acetate form, be included on the 503A bulks list.
In sport, the World Anti-Doping Agency's 2026 Prohibited List names BPC-157 under S0 and TB-500 under S2.3. GHK-Cu and KPV are not named, but S0 covers any pharmacological substance without current regulatory approval for human use, so the absence of a name is not a clearance.
Anhydrolabs supplies both blends for in-vitro laboratory research only, under the terms on the research-use page.
