A common copper-peptide blend comes in two versions: three peptides, or the same three plus a fourth. It sounds like regular versus extra strength. Most people assume the four-peptide version is just the three-peptide one turned up. It isn't.
Three-peptide vs four-peptide blends: same three compounds, and one more
Same three compounds. Same amounts. The four-peptide version adds a fourth called KPV. Nothing goes up. Something gets added. That makes it a different blend, not a stronger one.
The proof: do the math on the label
Here's what's actually going on.
Start with the milligrams. In a common version, the three-peptide blend is 50 mg of GHK-Cu, 10 mg of BPC-157 and 10 mg of TB-500. That's 70 mg. The four-peptide blend is that exact same 70 mg plus 10 mg of KPV, for 80 mg. Amounts vary by supplier, so the label on your vial is what counts.
Both are mostly copper peptide. That's why they're blue. GHK-Cu is 50 of the 70 mg in the three-peptide blend, about 71%. In the four-peptide blend it's 50 of 80, about 63%. It's a tiny peptide, just three amino acids, holding one copper ion, and the copper turns the powder blue. The other three are white. It's also the oldest of the four, first reported in human blood in 1973 (Pickart and Thaler, Nature New Biology 1973).
KPV is named after its own letters. Scientists write amino acids as one-letter codes, and K, P and V are lysine, proline and valine. That's the whole molecule. It's the last three links of alpha-MSH, a natural hormone 13 amino acids long. A 2008 review from the University of Münster explains why researchers zeroed in on that tail, which has been studied in cells and animals for inflammation signaling (Brzoska et al., Endocr Rev 2008). The FDA says it hasn't found any human exposure data on KPV at all (FDA).
So why should you care? One more compound is one more thing your certificate has to prove. Look for all four compounds named, and each one's amount measured separately. And the label should split the milligrams, not just give one total.
"Is every blend the same?" Nope. There's no standard recipe, and the names blends get sold under aren't used by any journal or regulator. The published research covers the four compounds one at a time. We haven't found a peer-reviewed study that tests either blend as a whole.
The big learning lesson
Keep reading: Does pH matter in peptide blends? · Why GHK-Cu copper peptide is everywhere · BPC-157 and TB-500: why they're studied together
Frequently asked questions
What's the difference between the three-peptide and four-peptide blends?
One compound. The three-peptide blend contains GHK-Cu, BPC-157 and TB-500. The four-peptide blend contains the same three, in the same amounts in the common version, plus KPV.
Where does KPV's name come from?
Its three amino acids: lysine (K), proline (P) and valine (V). The name is the whole molecule.
Are these blends FDA approved?
No. None of the four compounds is an FDA-approved drug, and neither blend is. They are sold for laboratory research use only.