RethinkPeptides
BPC-157 Evidence Quality

The Sikiric Problem: One Lab Behind 82% of BPC-157 Research

13 min read|March 25, 2026

BPC-157 Evidence Quality

82% from One Lab

Of 155 published BPC-157 studies, 127 list Predrag Sikiric or Sven Seiwerth as authors. Independent replication covers a fraction of the claimed benefits.

RethinkPeptides database analysis, 2026

RethinkPeptides database analysis, 2026

Single laboratory flask casting a large shadow over a research landscapeView as image

BPC-157 is one of the most discussed peptides in the wellness and sports recovery space. Claims about its healing properties span tendon repair, gut protection, neuroprotection, and cardiovascular function. But there is a structural problem with the BPC-157 evidence base that rarely gets discussed: the overwhelming majority of it comes from a single research group at the University of Zagreb in Croatia, led by Predrag Sikiric. Understanding why this matters requires looking at what that lab has produced, what the compound actually is, and what happens when you remove the Zagreb papers from the evidence pile.

This is not a personal critique of Sikiric. It is an observation about the structure of evidence that any scientist would flag before drawing conclusions about a compound's efficacy. When one lab generates more than 80% of the published data on any substance, the usual safeguards of science, independent replication and peer challenge, are functionally absent.

Key Takeaways

  • 127 of 155 BPC-157 studies in the RethinkPeptides database (82%) list Sikiric or Seiwerth as authors
  • A 2025 systematic review identified 544 BPC-157 articles but only 36 met inclusion criteria, with just 1 clinical study (Vasireddi et al., 2025)
  • Sikiric holds patent interests in BPC-157 through Diagen d.o.o. and is listed as an owner of PharmaCotherapia, the company that sponsored clinical trials
  • These financial interests were not disclosed in the published papers reviewed by investigative journalists
  • Independent replication from Chang Gung University (Taiwan) confirmed tendon fibroblast effects but did not test the musculoskeletal healing claims that drive consumer demand
  • All 127 Zagreb lab publications report positive or beneficial effects, a pattern inconsistent with typical pharmaceutical research where failure rates exceed 90%

The Scale of Single-Lab Dominance

The BPC-157 literature has an unusual structure. Predrag Sikiric published the first BPC-157 study in 1993, demonstrating hepatoprotective effects in rats with liver lesions.[1] Over the following three decades, the Zagreb lab produced a steady stream of papers extending BPC-157's claimed benefits to wound healing, gastric ulcers, tendon repair, bone healing, muscle injuries, vascular function, neurological protection, and more.

In the RethinkPeptides database, 127 of 155 BPC-157 studies (82%) include Sikiric or his longtime collaborator Sven Seiwerth as authors. The remaining 28 independent studies include reviews, in vitro experiments, and a small number of animal studies. Only a handful attempt to replicate the specific healing claims that have made BPC-157 popular.

Vasireddi et al. (2025) conducted a systematic review of BPC-157 in orthopaedic sports medicine and identified 544 articles from 1993 to 2024 across PubMed, Cochrane, and Embase.[2] After screening, only 36 met inclusion criteria: 35 preclinical studies and 1 clinical study. The clinical study was a case series by Edwin Lee, not a randomized controlled trial.

McGuire et al. (2025) published a narrative review of BPC-157 for musculoskeletal healing and noted that the "overwhelming majority of preclinical BPC-157 publications originate from a relatively small group of researchers based in Croatia."[3] They observed that all published studies report positive or beneficial effects, "suggesting a possible publication bias toward positive findings."

The Patent Problem

The concentration of research in a single lab becomes more concerning when financial interests are considered. Sikiric is named on BPC-157-related patent applications dating back to at least 1989. Croatian government records list him as an owner of PharmaCotherapia, the company that sponsored the only human clinical trials of BPC-157. He is also listed as CEO of Diagen d.o.o., a company whose website advertises "BPC 157 Stable Patent Rights for Sale."

Investigative reporting by Undark and STAT News in February 2026 documented that these financial interests were not disclosed in the published research papers. This is a violation of standard scientific disclosure practices. Most peer-reviewed journals require authors to declare any financial interests in the substances they study, specifically to allow readers to evaluate whether commercial incentives might influence study design, interpretation, or selective publication.

Józwiak et al. (2025) conducted a combined literature and patent review of BPC-157 and catalogued the scope of intellectual property claims around the peptide.[4] The patent filings describe BPC-157 applications across a range of conditions remarkably similar to the conditions studied in the Zagreb lab's publications. When the same researcher holds patents on a compound and produces the evidence base claiming that compound works, the integrity of the evidence depends entirely on trust rather than on the structural safeguards science is designed to provide.

What Independent Research Actually Shows

Removing the Zagreb lab papers from the BPC-157 evidence base leaves a much smaller, more nuanced picture.

Taiwan (Chang Gung University): Chang et al. (2011) confirmed that BPC-157 promotes tendon healing in a rat Achilles tendon model, demonstrating effects on tendon outgrowth, cell survival, and cell migration.[5] A follow-up study by the same group in 2014 showed that BPC-157 enhanced growth hormone receptor expression in tendon fibroblasts.[6] These are the strongest independent replications of BPC-157's tendon-related effects. They confirm biological activity at the cellular level but did not test the in vivo musculoskeletal healing outcomes that drive consumer demand.

Taiwan (Chung Shan Medical University): Hsieh et al. (2017) demonstrated that BPC-157's pro-angiogenic effects are associated with VEGFR2 activation and upregulation, providing mechanistic evidence for how the peptide might promote tissue repair through blood vessel formation.[7] This is important because angiogenesis promotion is also what raises cancer risk questions.

United Kingdom: Gwyer et al. (2019) reviewed BPC-157's role in musculoskeletal soft tissue healing and concluded that while preclinical evidence is "promising," the absence of human clinical trials means the compound's efficacy in humans remains unknown.[8]

United States (Edwin Lee): Lee et al. (2024) published a pilot study of BPC-157 in 6 patients with interstitial cystitis, reporting symptom improvement.[9] This is one of only two published human studies of BPC-157. With 6 participants, no control group, and no blinding, it cannot establish efficacy. Lee also published a 2025 safety study of intravenous BPC-157 infusion.[10]

Australia: Whitehouse (2025) published a commentary in Inflammopharmacology raising concerns about BPC-157's evidence base, noting the dominance of a single research group and the absence of robust clinical evidence despite decades of preclinical work.[11]

The pattern that emerges is this: independent labs have confirmed that BPC-157 is biologically active. It does something to cells in culture and to specific pathways in animal models. What no independent lab has confirmed is the full range of in vivo healing effects that the Zagreb lab claims and that consumers are paying for.

Why This Pattern Matters in Science

In pharmaceutical research, compounds typically fail. Industry-wide data shows that over 90% of drug candidates that enter clinical testing do not reach approval. In preclinical research, negative results are common. Experiments that do not find the expected effect are a normal part of the scientific process.

Against that baseline, BPC-157's publication record is unusual. All 127 studies from the Zagreb lab report positive results. Zero report null findings. Zero report that BPC-157 failed to produce an effect. This does not prove misconduct, but it is statistically implausible if the standard model of pharmaceutical research applies. The most likely explanations are publication bias (negative results exist but were not published), file-drawer effects (experiments that failed were abandoned rather than reported), or study designs that consistently favor positive outcomes.

Whitehouse (2025) framed this concern directly, noting that BPC-157's evidence base relies on a volume of positive preclinical data from a geographically concentrated research group without the confirmatory clinical evidence that would normally be expected after three decades of research.[11]

The Disclosure Gap

Scientific publishing has a mechanism for handling situations where researchers have financial interests in their subjects: conflict of interest disclosures. When authors declare that they hold patents, own companies, or receive royalties related to their research topic, readers and reviewers can factor that information into their evaluation of the work.

The February 2026 investigations by Undark and STAT News documented that Sikiric's published papers did not disclose his financial connections to BPC-157 through PharmaCotherapia, Diagen, or his patent interests. This is a separate issue from the science itself. The biological activity of BPC-157 is not changed by whether its primary researcher disclosed his patents. But the credibility of a single-lab evidence base depends heavily on transparency, and the absence of disclosure undermines the trust that such evidence would otherwise warrant.

The situation is further complicated by the fact that Sikiric's lab produced clinical trial data for BPC-157 (registered as PL-10 and PL14736 under the Croatian pharmaceutical company Pliva) that was not published in indexed journals accessible through PubMed. Multiple trial registrations exist, but the full data from these trials has not been made publicly available in a format that allows independent evaluation.

How to Read the BPC-157 Literature Now

None of this means BPC-157 does not work. It means the evidence for its claimed effects is structurally weak, not because the studies are individually flawed, but because the body of evidence lacks the diversity and independence that science requires before drawing firm conclusions.

Reading the BPC-157 literature responsibly means:

  1. Checking the author list. If Sikiric or Seiwerth is an author, the study is from the Zagreb lab. This does not invalidate the findings, but it means they have not been independently replicated until another lab reproduces them.

  2. Distinguishing in vitro from in vivo. Independent labs have confirmed BPC-157's effects on cells in culture. That is not the same as confirming it heals injuries in living organisms.

  3. Recognizing the clinical gap. After 30+ years of research, BPC-157 has only two published human studies, both from a single U.S. physician, neither randomized or controlled. The reasons for this gap are multiple, but the gap itself is a fact.

  4. Weighing the patent interests. The primary researcher holds undisclosed financial interests in the compound. This does not prove bias, but it means the evidence should meet a higher bar for independent confirmation.

The safety data from animal studies and supply chain quality concerns add further layers to the evidence picture. BPC-157 may ultimately prove to be a valuable therapeutic compound. But the current evidence base, dominated by a single lab with undisclosed patent interests, is not sufficient to know.

The Bottom Line

The BPC-157 evidence base has a structural problem: 82% of published studies come from a single lab at the University of Zagreb, led by a researcher with undisclosed patent interests in the compound. Independent replication has confirmed biological activity at the cellular level but has not reproduced the in vivo healing claims that drive consumer demand. After three decades of research, only two human studies exist, neither randomized nor controlled. The evidence is not zero, but it lacks the diversity and independence that science requires before treating any compound's efficacy as established.

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