What is inside
This is not one substance. It is two separate lab-made peptides, BPC-157 and TB-500, sold mixed together in one vial as a research product. BPC-157 is a 15-amino-acid fragment of a protein reported in stomach juice, studied mostly in rats. TB-500 is a 7-amino-acid piece of thymosin β4, a natural protein found in almost every cell. Neither is an approved medicine anywhere.
There is no official recipe. How much of each peptide goes into a vial, and in what ratio, varies by seller and is not standardised. No pharmacopoeia or regulator defines the product, so the label is the only description of what is inside. Each ingredient has its own page on this site, summarised in the next two sections.
The product is a physical mixture of two unrelated synthetic peptides. BPC-157 is the linear pentadecapeptide Gly-Glu-Pro-Pro-Pro-Gly-Lys-Pro-Ala-Asp-Asp-Ala-Gly-Leu-Val (C62H98N16O22, 1419.5 g/mol). TB-500 is Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln (Ac-LKKTETQ, C38H68N10O14, 889.0 g/mol), residues 17–23 of thymosin β4, N-acetylated; this is how FDA identifies it. The name is not used consistently, though: the 2026 rat study of the pair describes TB-500 as “synthetic thymosin beta-4”, the full 43-residue protein, so the identity of the second component in a given product cannot be assumed.
The two peptides are not chemically linked, and no study of their compatibility, stability or degradation when stored together in one vial or solution was found. Per-vial amounts and ratios are set by each seller and are not standardised, and no reference standard exists for the mixture. No human pharmacokinetic data exist for injected or oral BPC-157 or for TB-500, and nothing is known about the combination, including whether one peptide alters the absorption, distribution or clearance of the other.
Ingredient: BPC-157
BPC-157 is a chain of 15 amino acids first described in 1993 by a research group at the University of Zagreb in Croatia. Almost everything known about it comes from rats and mice, where it has been reported to speed the healing of cut tendons, muscles and ligaments and to protect the stomach lining from damage. Most of those studies come from the same Croatian group, with little independent replication.
In people, no controlled trial has been published in full. The FDA’s 2026 review found only a short 2005 conference summary of a two-week, placebo-controlled enema study in 53 people with ulcerative colitis, which it judged too thin to show whether the peptide works or is safe. A small oral safety study from 2015 never reported results, and a trial registered in Arkansas in 2026 had not started recruiting when this was written; a second 2026 registry entry comes from a sponsor that also posted a self-described fictional record. What BPC-157 does in the human body is not known.
No receptor for BPC-157 has been identified. Mechanisms proposed from animal and cell work include up-regulation of VEGFR2 with activation of the VEGFR2–Akt–eNOS pathway, modulation of the nitric-oxide system, and increased growth-hormone-receptor and EGR-1 expression in fibroblasts. None has been tested in humans. Typical rodent regimens were 10 µg/kg or 10 ng/kg intraperitoneally or in drinking water, and the peptide is reported to be stable in gastric juice.
Human data: FDA’s 2026 briefing identified one randomized, double-blind, placebo-controlled study, reported only as a meeting abstract (Ruenzi et al., 2005): 53 people with mild to moderate ulcerative colitis received an 80 mg BPC-157 (PL 14736) enema or placebo daily for two weeks, and FDA judged the data inadequate on efficacy and safety. Abstracts on enema dosing reported BPC-157 undetectable in plasma; no pharmacokinetic data exist after oral or subcutaneous dosing. Registered studies: NCT02637284 (Phase 1, oral tablets, 2015, no results posted), NCT07437547 (Phase 2, subcutaneous once daily for 14 days in hamstring strain, listed as recruiting since February 2026; its sponsor also posted the self-described fictional TB-500 record discussed below, so it is not counted as a confirmed trial) and NCT07803250 (Phase 1, subcutaneous once daily for 90 days after rotator-cuff repair, not yet recruiting). FDA’s 2023 Category 2 assessment cited immunogenicity risk, peptide-related impurities and a lack of human safety information.
Ingredient: TB-500
TB-500 is a lab-made copy of seven amino acids taken from thymosin β4, a natural protein found in almost every cell, where it holds actin, the building block of the cell’s internal skeleton. Thymosin β4 was first sequenced in 1981 at George Washington University.
The key point is that TB-500 is not thymosin β4. The human trials often quoted for TB-500, such as eye drops for dry eye and for a nerve-damage condition of the cornea, used the full 43-amino-acid protein under drug codes such as RGN-259, with mixed results. No genuine human study of the seven-amino-acid fragment was found. The one entry naming TB-500 on the US trials registry, posted in 2026, describes itself as a fictional example record, so it cannot be counted as a trial. Its effects and side effects in people are unknown.
TB-500 (Ac-LKKTETQ) reproduces the LKKTET actin-binding motif (residues 17–22) of thymosin β4. Full-length Tβ4 is reported in preclinical models to promote keratinocyte and endothelial migration, angiogenesis and cardiomyocyte survival and to reduce inflammatory cytokine release (Goldstein et al., 2005). Whether the isolated fragment reproduces those effects is unsettled, because other activities, such as those of the N-terminal Ac-SDKP tetrapeptide, reside elsewhere in the molecule.
Full-length Tβ4 trials: ARISE-2 (n=601) and ARISE-3 (n=700) in dry eye did not meet their primary endpoints; SEER-1 (n=18) in neurotrophic keratopathy reported complete healing in 6 of 10 on RGN-259 versus 1 of 8 on placebo at day 29 (p=0.0656). For the fragment itself, no genuine trial was found. The only ClinicalTrials.gov record naming it, NCT07487363 (posted March 2026, a Phase 1/2 design in stable atherosclerotic cardiovascular disease), states in its own summary that it is “a fictional study” and an example record, and it discloses no doses. FDA stated in 2023 that it had not identified any human exposure data for the fragment. No pharmacokinetic data have been published.
Why researchers might study these together
The case for mixing them is a hypothesis, not a finding. In animal and lab studies, BPC-157 has mostly been linked to the growth of new blood vessels and to nitric-oxide signalling, while thymosin β4, the parent protein of TB-500, has been linked to how cells crawl into a wound. The suggestion is that two peptides acting on different parts of tissue repair might add up.
That idea has been tested once, in rats. A 2026 study of 32 rats with repaired Achilles tendons compared each peptide with the pair and found the combination did no better than either alone. No clinical trial has tested the combination in people. The only human reports found are a small, uncontrolled clinic chart review and one adverse-event report sent to the FDA.
The proposed rationale rests on distinct mechanisms from separate preclinical literatures: VEGFR2–Akt–eNOS and nitric-oxide signalling for BPC-157, and G-actin sequestration with downstream cell migration and angiogenesis for thymosin β4. Both are hypotheses from studies of each peptide alone, and both converge on angiogenesis, so redundancy is as plausible as complementarity.
The only controlled test of the pair is Biçer et al. (2026): 32 Sprague-Dawley rats with transected and repaired Achilles tendons received intraperitoneal BPC-157 10 µg/kg/day, TB-500 60 µg/kg/day, both, or no treatment for four weeks. TB-500 alone significantly improved load to failure and Bonar score; the combination improved Movin score (p=0.040) but showed no additional effect over either agent alone. The abstract calls TB-500 “synthetic thymosin beta-4” without specifying the fragment.
No registered trial has tested the combination. Lee and Padgett (2021) reported a retrospective phone survey at one Florida clinic in which 4 of 16 knee-pain patients had intra-articular BPC-157 plus “TB4” and 3 of those 4 reported relief, with no control group or standardised outcome measure.
Regulatory picture
Approval: no regulator anywhere has approved BPC-157, TB-500 or any product combining them, and no regulator has evaluated the combination at all. FDA decisions apply to each peptide separately.
Compounding: in September 2023 the FDA placed each peptide, on its own review, in Category 2, the group it said raises significant safety risks, so pharmacies compounding with them could face FDA action. By April 2026 its page listed both as withdrawn from that category by their nominators. In July 2026 an FDA advisory committee voted narrowly in favour of allowing each peptide, BPC-157 for ulcerative colitis and TB-500 for wound healing; blends were not on the agenda. The FDA had not made a final decision when this was written.
Sport: the World Anti-Doping Agency prohibits both peptides at all times, so any product containing them is prohibited too.
Approval: none. No IND-stage programme for the combination could be verified, and neither component has a verified US IND.
Compounding: under section 503A(b)(1)(A)(i) of the FD&C Act, each bulk drug substance in a compounded product must independently comply with a USP or NF monograph, be a component of an FDA-approved drug, or appear on the 503A bulks list (21 CFR 216.23). A two-peptide product therefore has no status of its own; it inherits the status of each ingredient. Both peptides entered Category 2 of the interim policy on 2023-09-29 and are listed as withdrawn by the nominators on FDA’s page updated 2026-04-22; neither is on the bulks list. On 2026-07-23 the Pharmacy Compounding Advisory Committee reviewed BPC-157 and TB-500 (free base and acetate of each) as separate substances and voted narrowly for each; FDA rulemaking is required before either vote has effect. This article records compounding status as unknown, the status both components currently share.
Anti-doping: the 2026 WADA Prohibited List names thymosin β4 and its derivatives, e.g. TB-500, under S2.3 and names BPC-157 as an example under S0, non-approved substances.
