Klow peptide blend: the four peptides in the vial, what each one's research covers, and what a Klow COA has to show

What Klow is: a trade name for a four-peptide vial#

Klow is a commercial name for a fixed mixture of four peptides in one lyophilized vial: GHK-Cu, BPC-157, TB-500 and KPV. It is not a scientific name. No regulator or pharmacopeia defines it, and no peer-reviewed study has examined the four-peptide mixture itself. What the name tells you is which family of product you are looking at. What matters is the component list, the amount of each component in the vial, and the test report for the lot.

On Renuvia's catalog the Klow product page lists an 80 mg vial. The lot tested in October 2026 contained, by the laboratory's measurement, 53.82 mg GHK-Cu, 10.81 mg BPC-157, 10.05 mg TB-500 and 10.27 mg KPV, which is consistent with a 50/10/10/10 mg composition ^[1]. Klow is the four-peptide sibling of the three-peptide Glow Blend; KPV is the one component Klow has and Glow does not.

The four Klow peptides at a glance#

The four were grouped by sellers because their separate research histories share two themes: inflammation and tissue repair. That is a marketing rationale, not a finding. Each component's evidence is summarized below, with the system each study used, so you can see what has and has not been measured.

GHK-Cu: the copper peptide that makes up most of the vial#

GHK is the tripeptide glycyl-histidyl-lysine. It was first described in 1973 as a factor in human serum that affected liver cells in culture ^[2]. GHK binds copper(II) readily, and the copper complex is what "GHK-Cu" refers to. Because GHK-Cu accounts for roughly five-eighths of a Klow vial by mass, its properties dominate the vial's appearance: the copper complex gives Klow its characteristic blue tint, which is why Klow is the only blue powder in Renuvia's catalog.

The most cited laboratory finding is from 1988, when Maquart and colleagues reported that GHK-Cu increased collagen synthesis in cultured human fibroblasts ^[3]. Later work, much of it reviewed by Pickart and Margolina in 2018, used gene-expression profiling to describe how GHK-Cu changed the expression of a large number of genes in cultured cells ^[4]. Human data are limited to small studies of topical cosmetic formulations. A fuller account is in the GHK-Cu research explainer.

BPC-157: the most studied component, almost entirely in rodents#

BPC-157 is a 15-amino-acid sequence derived from a protein found in human gastric juice. Most of the literature is from one research group and uses rodent injury models. A representative cell study found that BPC-157 increased the outgrowth, survival and migration of tendon cells in culture ^[5]. A 2025 systematic review in HSS Journal identified 35 preclinical studies and a single human case series, and concluded that human evidence was lacking ^[6].

In July 2026, FDA's Pharmacy Compounding Advisory Committee reviewed a briefing document on BPC-157 that summarized the available studies and the gaps in human safety data ^[7]. The BPC-157 product page and the research library carry the detail.

TB-500: a fragment of thymosin β4, not the whole protein#

TB-500 is not thymosin β4. It is a seven-residue, N-terminally acetylated fragment of it (Ac-LKKTETQ, residues 17–23). Esposito and colleagues synthesized and characterized this fragment in 2012 after identifying it in a product marketed as TB-500 ^[8]. Much of the research people attribute to TB-500 was done with full-length thymosin β4, a 43-amino-acid protein, so it does not transfer to the fragment automatically.

FDA's 2026 briefing document on TB-500 stated that the agency identified no human data for the fragment ^[9]. One rat study compared BPC-157 and TB-500 in a rat Achilles tendon model, assessed by histology and biomechanical testing ^[12]. The TB-500 explainer separates the fragment's record from the full protein's.

KPV: the tripeptide that distinguishes Klow from Glow#

KPV is lysine-proline-valine, the last three residues of α-melanocyte-stimulating hormone. Its research is concentrated in intestinal inflammation. Dalmasso and colleagues showed in 2008 that KPV is carried into intestinal epithelial cells by the peptide transporter PepT1 and reduced inflammatory signaling in cell culture and in a mouse colitis model ^[10]. In the same year, Kannengiesser and colleagues reported anti-inflammatory effects of KPV in two mouse models of inflammatory bowel disease ^[11]. There are no human studies of KPV. The KPV research explainer covers the sequence, identifiers and each study in more detail.

What has not been studied: the mixture#

No published study has tested GHK-Cu, BPC-157, TB-500 and KPV together, in any system. That means there are no data on whether the four interact, whether they are stable together in solution, or whether the findings for any one component hold in the presence of the other three. Anything written about "Klow" as a whole is an extrapolation from four separate literatures, most of them cell and animal work. Our guide to peptide blends explains why this matters when you read a listing for any multi-peptide vial.

Regulatory status of the four components#

• None of the four is an approved drug in the United States or, to our knowledge, anywhere else.
• BPC-157, TB-500, GHK-Cu and KPV all appear on FDA's page of bulk drug substances nominated for compounding that may present significant safety risks; BPC-157 and TB-500 were reviewed by FDA's Pharmacy Compounding Advisory Committee in July 2026 ^[7][9][13].
• BPC-157 falls under WADA's section S0 (non-approved substances) and TB-500, as a thymosin β4 derivative, is named in section S2.3 of the 2026 Prohibited List ^[14].
• These listings describe compounding and sport-testing status. They do not change the research-use-only status of the vial.

How to read a Klow Certificate of Analysis#

A single-peptide COA has one main HPLC peak and one identity result. A four-peptide vial needs four of each. For lot RN-2610-KLOW, the laboratory ran HPLC-UV for purity and LC-MS for identity, reported an overall purity of 99.69%, confirmed identity for each component, and listed the measured amount of each of the four peptides ^[1]. When you read a Klow report from any seller, check that:

1. All four peptides are named individually, each with an identity result from mass spectrometry, not a single "identity confirmed" line for the vial.
2. The amount of each component is reported in milligrams, so you can compare it with the label. A single purity percentage says nothing about whether the ratio is what the label claims.
3. The lot number on the report matches the lot on the vial, and the laboratory is named with a report or accession number you can check with the lab.
4. The report is for a Klow lot, not a report for one of the single peptides shown in its place.

Renuvia publishes each tested Klow lot's report in the COA library. The guides to reading a Certificate of Analysis and to HPLC and mass spectrometry explain what each section of the report means.