BPC-157, GHK-Cu and Thymulin: What Happens When You Actually Read the Studies

Patients ask me about peptides almost every week now. Someone heard about BPC-157 on a podcast, or a training partner is injecting something for a shoulder, or a skincare line promises that copper peptides will do things copper peptides have never been shown to do.

I should say up front that we don’t currently offer peptide therapy at either of our locations, and we don’t sell any of the three compounds in this article. I have no product to move here. What I have is a habit that took me years of training to build, and it’s the only thing I actually want to hand you: when someone cites a study, go read the study.

I did that for three peptides. Here’s what I found.

Where does “BPC-157 fights tumors” actually come from?

Almost every claim that BPC-157 has anti-tumor activity traces back to a single source, and that source is a conference abstract from 2004.

It’s Radeljak, Seiwerth and Sikirić in Melanoma Research, volume 14, pages A14 to A15. Two pages. The “A” in front of the page numbers tells you it’s a meeting supplement — a poster, essentially. It has never been developed into a full peer-reviewed paper in twenty-two years. Two of its three authors are from the Zagreb laboratory that discovered BPC-157 in the first place.

None of that makes it fraudulent. Conference abstracts are a normal part of science. But an abstract is a preliminary finding presented for discussion, not a result that has survived peer review, and it gets cited in reviews and on vendor pages in language that makes it sound like established cancer therapy. It isn’t.

Meanwhile, work from a group with no Zagreb affiliation — Hsieh and colleagues in the Journal of Molecular Medicine — showed BPC-157 upregulates VEGFR2 and promotes new blood vessel formation. That’s the mechanism by which it’s supposed to help you heal. It’s also, in a different context, one of the mechanisms by which tumors establish a blood supply. Both things are true at once.

What does the FDA’s own review say about the cancer question?

I expected to find a debate about the evidence. What I found was an absence of evidence, stated plainly by the government.

The FDA’s briefing document for the July 2026 Pharmacy Compounding Advisory Committee has a section headed “Carcinogenicity.” Its entire content is that no carcinogenicity studies of BPC-157 were submitted, and none were found.

Nobody has looked. That’s different from “it’s dangerous,” and it’s different from “it’s safe.”

The best safety data that does exist — Xu and colleagues, 2020, in mice, rats, rabbits and dogs — found no genetic or embryo-fetal toxicity, which means the peptide doesn’t appear to damage DNA. I want to be fair to that study: it’s independent, well-conducted, and reassuring as far as it goes. It just doesn’t go where people think it does. Longest exposure was 28 days. A carcinogenicity study runs two years and asks a different question entirely: not whether something breaks DNA, but whether it feeds a process already underway.

Two Polish research groups and the Zagreb group are currently arguing this out in print — the original review, the rebuttal, and the reply are all open access. Read all three. Watching working scientists disagree is more educational than any summary I could write.

One thing I’ll add because it surprised me: capsules are not the cautious option. There is no human pharmacokinetic data for BPC-157 taken by mouth, in any published study. The peptide does survive stomach acid — it’s how it was discovered — but surviving your stomach and reaching your knee are not the same event. And whatever the capsule is, it isn’t a lawful dietary supplement: the FDA has flagged it as a bulk substance presenting significant safety risks, including contamination with other substances. It’s banned for service members and prohibited in competition by WADA. So whatever the delivery route, the long-term safety data is missing and the compound is not FDA-approved for any indication.

Who is telling you copper peptides fight cancer?

With GHK-Cu, the literature runs the opposite direction — it’s mostly reassuring — and that’s exactly what made me look harder.

The central paper is Skin Regenerative and Anti-Cancer Actions of Copper Peptides, published in Cosmetics in 2018 by Loren Pickart and Anna Margolina. Pickart isolated GHK in 1973. He built companies around copper peptides. The paper states that the authors declare no conflict of interest, and its first reference is Pickart’s own US patent.

Then look at reference 6 in that same paper. It’s his 1973 doctoral thesis, and the title is A Tripeptide from Human Serum Which Enhances the Growth of Neoplastic Hepatocytes and the Survival of Normal Hepatocytes.

I want to be careful here, because it would be easy and wrong to turn that into a scare. Hepatoma cell lines were a standard culture system in 1973, and that thesis is not evidence that GHK causes cancer in people. But the founding document describes growth enhancement of neoplastic cells, and the modern review by the same author is titled “Anti-Cancer Actions,” and it cites the thesis. That drift is worth noticing. It took me about ten minutes to find, in a reference list anyone can open.

Is the research on thymulin even about thymulin?

Thymulin has the best underlying science of the three, and the most confused marketing.

The foundational work is excellent: Bach, Dardenne, Pléau and Rosa in Nature in 1977, from Hôpital Necker in Paris. Thymulin is a genuine hormone — a nine-amino-acid peptide from thymic epithelial cells, with a measurable blood level that falls with age. That’s real endocrinology, published in one of the best journals in the world.

The problem is that three different thymus compounds circulate under nearly identical names. Thymulin is the nonapeptide above. Thymalin is a bovine thymus extract — a mixture, not a defined molecule — studied mostly in older Russian literature. Thymosin alpha-1 is a 28-amino-acid synthetic peptide, and it’s the only one of the three with modern randomised trials.

I found vendor pages selling thymulin while citing clinical results that belong to thymalin. Different substance, different studies, same paragraph. That’s not a weak study being oversold — it’s evidence transplanted from one molecule onto another.

The human thymulin literature itself is lacking. The rheumatoid arthritis “open trial” people point to is Faure and colleagues, 1987, and PubMed classifies it as a Letter. Three pages, no abstract. No thymulin therapy has been approved anywhere.

There’s also a detail the marketing skips. Thymulin without zinc bound to it is biologically inert. And most of the human data showing low thymulin comes from zinc-deficient or malnourished people. So if you’re genuinely worried about immune aging, ask your physician to check your zinc levels. It costs almost nothing and it’s the only part of this story with a clear answer.

What would change my mind?

A properly powered randomised controlled trial with real endpoints and long-term follow-up. That’s it. That’s the whole bar, and it’s the same bar I’d apply to a drug a pharmaceutical rep brought into my office.

Right now none of these three clear it. There’s no independent dosing guidance from any medical society — the FDA notes that with BPC-157, doses a thousandfold apart produced the same effect in animals, which is another way of saying nobody knows what a dose is.

So my position, and my partner’s, is simple: if I’d hesitate to put it in my own arm, I can’t in good conscience put it in yours. That’s not a claim these compounds are dangerous. I don’t know that they’re dangerous. What I know is that nobody has done the work to find out — and that the absence of a study is being sold to you as the absence of a problem.

If you’re using one of these, I’m not going to lecture you. But go find the citation behind the claim that convinced you, and open it. Sometimes it’s a Nature paper. Sometimes it’s a poster from 2004.

References

Radeljak S, Seiwerth S, Sikirić P. BPC 157 inhibits cell growth and VEGF signalling via the MAPK kinase pathway in the human melanoma cell line. Melanoma Research. 2004;14(4):A14–A15 (conference abstract).

Hsieh MJ, Liu HT, Wang CN, et al. Therapeutic potential of pro-angiogenic BPC157 is associated with VEGFR2 activation and up-regulation. Journal of Molecular Medicine. 2017;95(3):323–333. doi:10.1007/s00109-016-1488-y

Xu C, Sun L, Ren F, et al. Preclinical safety evaluation of body protective compound-157, a potential drug for treating various wounds. Regulatory Toxicology and Pharmacology. 2020;114:104665. doi:10.1016/j.yrtph.2020.104665

Józwiak M, Bauer M, Kamysz W, Kleczkowska P. Multifunctionality and possible medical application of the BPC 157 peptide — literature and patent review. Pharmaceuticals. 2025;18(2):185. doi:10.3390/ph18020185

Sikirić P, Seiwerth S, Skrtic A, et al. Comment on Józwiak et al. Pharmaceuticals. 2025;18(10):1450. doi:10.3390/ph18101450

Józwiak M, Bauer M, Kamysz W, Kleczkowska P. Reply to Sikirić et al. Pharmaceuticals. 2025;18(10):1451. doi:10.3390/ph18101451

U.S. Food and Drug Administration. Briefing Document, Pharmacy Compounding Advisory Committee, 23–24 July 2026.

U.S. Food and Drug Administration. Certain bulk drug substances for use in compounding may present significant safety risks.

Pickart L, Margolina A. Skin Regenerative and Anti-Cancer Actions of Copper Peptides. Cosmetics. 2018;5(2):29. doi:10.3390/cosmetics5020029

Bach JF, Dardenne M, Pléau JM, Rosa J. Biochemical characterisation of a serum thymic factor. Nature. 1977;266(5597):55–57. doi:10.1038/266055a0

Faure GC, Bene MC, Thomas P, Tamisier JN. An open trial of thymulin (FTS-Zn) in rheumatoid arthritis patients: sequential clinical and immunological follow-up. Clinical and Experimental Rheumatology. 1987;5(3):291–293 (letter).