BPC-157 and TB-500 are often mentioned together, but they are unrelated molecules: BPC-157 is a 15-amino-acid fragment of a protein reported in human gastric juice, while TB-500 is a 7-amino-acid fragment of thymosin beta-4, a protein found in nearly every human cell. What they share is the shape of their evidence, which is mostly rodent and cell-culture research, with no completed randomized human trial published for either compound.
We found no study that compares the two head to head. The comparison below sets their published records side by side, names the model each finding came from, and says plainly where the record runs out.
At a glance
| BPC-157 | TB-500 | |
|---|---|---|
| What it is | 15-amino-acid peptide, sequence GEPPPGKPADDAGLV | 7-amino-acid acetylated fragment of thymosin beta-4 (residues 17 to 23) |
| Parent molecule | "Body protection compound," reported in human gastric juice | Thymosin beta-4, a 43-amino-acid protein |
| Main research group | University of Zagreb, from the early 1990s | Much of the parent-protein work at the NIH and George Washington University |
| Proposed mechanisms | Angiogenesis (VEGFR2), FAK-paxillin signaling, nitric oxide system | Actin binding, cell migration (largely inferred from the parent protein) |
| Evidence base | Dozens of animal and in vitro studies; a handful of small human reports | Very little published work on the fragment itself; the literature mostly concerns the full protein |
| Human trials | No completed randomized trial published in full | None identified by the FDA for the fragment |
| FDA approval | None | None |
| Sport | Prohibited (WADA S0) | Prohibited by name (WADA S2) |
Origins
BPC-157 traces to work by Predrag Sikiric and colleagues at the University of Zagreb, who described a gastric protein they called body protection compound in the early 1990s and studied a 15-residue partial sequence of it. The same group has produced most of the literature since. In the 2000s the peptide was developed under the code PL 14736 as a candidate treatment for inflammatory bowel disease, a program that left behind meeting abstracts rather than full publications.
TB-500 starts from thymosin beta-4, which was isolated from calf thymus and sequenced in 1981 (Low, Hu and Goldstein, PNAS). Thymosin beta-4 was later found in most cell types and in wound fluid, where it binds actin, the protein that forms much of the cell's internal scaffolding. According to the FDA's 2026 review, TB-500 is understood today to be the acetylated fragment covering residues 17 to 23 of that protein, the region associated with actin binding. The FDA also noted that "TB-500" is a common name rather than an adopted drug name, and that it has encountered different salts and even different molecules sold under it.
Proposed mechanisms
For BPC-157, the mechanistic work is mostly in cells and rats. Chang and colleagues (Journal of Applied Physiology, 2011) reported that BPC-157 increased migration and survival of rat tendon fibroblasts in culture and activated the FAK-paxillin pathway. Hsieh and colleagues (Journal of Molecular Medicine, 2017) reported increased blood-vessel formation in a chick membrane assay and in a rat hind-limb ischemia model, with increased expression of the receptor VEGFR2 in human endothelial cells in culture. The Zagreb group has proposed interactions with the nitric oxide system across many of its papers, summarized in a 2025 review (Sikiric et al., Pharmaceuticals).
For TB-500, the mechanism is mostly borrowed. The parent protein's actin binding is well established, and Bock-Marquette and colleagues (Nature, 2004) reported that full-length thymosin beta-4 activated a survival pathway and improved cardiac function in mice after coronary artery ligation. Whether the seven-residue fragment does the same things is a separate question. The FDA's review pointed out that acetylation changes how a peptide behaves, so results for the unmodified sequence cannot simply be transferred to TB-500, and it cited a 2024 in vitro study (Rahaman et al.) in which TB-500 did not change wound closure in cultured fibroblasts compared with a control.
What kind of evidence exists
Mostly animal and in vitro, for both, and it is worth being plain about that.
For BPC-157, a 2025 systematic review in HSS Journal (Vasireddi et al.) searched the orthopedic literature from 1993 to 2024 and included 36 studies, of which 35 were preclinical and one was clinical. A representative example of the animal work is Staresinic and colleagues (Journal of Orthopaedic Research, 2003), who reported improved biomechanical, functional and microscopic healing of transected Achilles tendons in rats treated with BPC-157 compared with saline controls.
For thymosin beta-4, the full protein, the animal record includes Malinda and colleagues (Journal of Investigative Dermatology, 1999), who reported faster re-epithelialization of full-thickness wounds in rats. The parent protein also reached human trials: a European phase 2 study of a topical thymosin beta-4 formulation in 73 patients with venous leg ulcers (Guarnera et al., Annals of the New York Academy of Sciences, 2010) found its safety comparable to placebo, with efficacy results the authors described as suggestive. No thymosin beta-4 product has been approved. None of that work used TB-500.
The human record
For BPC-157, the FDA's briefing document for its July 2026 advisory meeting identified five published human reports. They were two meeting abstracts from early safety studies, one meeting abstract from a small randomized ulcerative colitis study, a retrospective chart review of knee pain patients at a single Florida clinic, a single-arm study of 12 women with interstitial cystitis, and a two-person safety report. A phase 1 trial registered on ClinicalTrials.gov (NCT02637284) has no posted results. The FDA concluded the data were inadequate to support efficacy and that there was insufficient clinical safety information to characterize the compound.
For TB-500, the FDA's review said it had not identified human exposure data for products containing the fragment by any route. That is the clearest difference between the two: BPC-157 has a thin human record, and TB-500 has none on file with the agency.
Regulatory status
Neither compound is FDA-approved for any use. Both were among the peptides the FDA had placed in Category 2 of its interim compounding policy, the category for substances that may present significant safety risks, and both were removed from it in April 2026 after their nominators withdrew. At the FDA's July 23 and 24, 2026 advisory meeting, FDA staff proposed against adding either to the 503A bulks list; the committee recommended both, including an 8 to 6 vote with one abstention for BPC-157. That recommendation is not binding and is not an approval, and we could find no proposed or final rule as of this writing. Our guide to FDA approval explains the difference.
In sport, BPC-157 is prohibited under WADA's S0 category for non-approved substances, and thymosin beta-4 and its derivatives, with TB-500 named as an example, are prohibited under S2.
For the wider context on this group, including KPV, see our review of the repair peptides.
Frequently asked questions
Is TB-500 the same as thymosin beta-4?
No. Thymosin beta-4 is a 43-amino-acid protein with a substantial research record. TB-500 is a seven-residue acetylated fragment of it, and the FDA found no human data on the fragment.
Which has more research, BPC-157 or TB-500?
BPC-157 has the larger body of work on the molecule itself, nearly all of it in animals and largely from one research group. Most of what is written about TB-500 actually describes the parent protein.
Has either been tested in a randomized human trial?
No completed randomized trial of either has been published in full. The closest is a 2005 meeting abstract describing a small ulcerative colitis study of BPC-157, which the FDA judged inadequate to draw conclusions from.
Are BPC-157 and TB-500 legal?
Neither is approved as a drug. Their compounding status is under review following the July 2026 advisory vote. Both are prohibited in sport.
Sources:
- Staresinic et al., J Orthop Res, 2003 (rat Achilles tendon)
- Chang et al., J Appl Physiol, 2011 (rat tendon fibroblasts, FAK-paxillin)
- Hsieh et al., J Mol Med, 2017 (VEGFR2, chick membrane, rat hind limb, human endothelial cells)
- Vasireddi et al., HSS Journal, 2025 (systematic review, 36 studies)
- Sikiric et al., Pharmaceuticals, 2025 (the Zagreb group's review of proposed angiogenesis and nitric oxide mechanisms)
- Low, Hu and Goldstein, PNAS, 1981 (sequence of thymosin beta-4)
- Malinda et al., J Invest Dermatol, 1999 (rat wound model)
- Bock-Marquette et al., Nature, 2004 (mouse cardiac model)
- Guarnera et al., Ann N Y Acad Sci, 2010 (phase 2, venous ulcers)
- Goldstein et al., Expert Opin Biol Ther, 2012 (review of thymosin beta-4)
- FDA briefing document, BPC-157-related bulk drug substances, PCAC, July 2026
- FDA briefing document, TB-500-related bulk drug substances, PCAC, July 2026
- FDA, Certain bulk drug substances for use in compounding that may present significant safety risks
- Mintz, FDA's advisory committee votes on peptides, July 29, 2026
- ABC News via Good Morning America, FDA advisory committee votes to add BPC-157, July 23, 2026
- USADA, BPC-157: experimental peptide prohibited
- WADA 2026 Prohibited List, as published in the Dutch treaty series (S0 names BPC-157; S2 names thymosin beta-4 and TB-500)
No compound discussed in this review is FDA-approved. Nothing above is dosing guidance or a treatment claim. Research use only.
For research use only · Not for human or veterinary use · No research compound discussed here is FDA-approved for any indication