What is inside
This is not one substance. It is two lab-made peptides (short chains of amino acids) mixed in one vial. They are called BPC-157 and TB-500. The mix is sold as a research product. BPC-157 is a chain of 15 amino acids. It comes from a protein reported in stomach juice. It has been studied mostly in rats. TB-500 is a piece of 7 amino acids. It is cut from thymosin β4, a natural protein found in almost every cell. Neither peptide is an approved medicine anywhere.
There is no official recipe. Each seller decides how much of each peptide goes in a vial. The ratio between them also varies. It is not standardised. No official drug standard or regulator defines this product. So the label is the only description of what is inside. Each ingredient has its own page on this site. The next two sections sum them up.
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. A research group at the University of Zagreb in Croatia first described it in 1993. Almost everything known about it comes from rats and mice. In those animals, it was reported to speed healing of tendons, muscles and ligaments that had been cut. It was also reported to protect the stomach lining from damage. Most of these studies come from the same Croatian group. Few other groups have checked the results.
No controlled trial in people has been published in full. The FDA reviewed the evidence in 2026. It found only a short 2005 conference summary. That study lasted two weeks. It compared a BPC-157 enema with a dummy treatment (placebo) in 53 people with ulcerative colitis (a bowel disease). The FDA said it was too thin to show whether the peptide works or is safe. A small safety study of BPC-157 by mouth from 2015 never reported results. A trial registered in Arkansas in 2026 had not started taking patients when this was written. A second 2026 registry entry comes from a sponsor that also posted a record it called fictional. 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 7 amino acids. They are taken from thymosin β4, a natural protein found in almost every cell. Inside cells, thymosin β4 holds on to actin. Actin is a building block of the cell’s inner frame. The make-up of thymosin β4 was first worked out in 1981 at George Washington University.
The key point: TB-500 is not the same as thymosin β4. People often quote human trials for TB-500. But those trials used the full protein, which has 43 amino acids. They used drug codes such as RGN-259. They tested eye drops for dry eye and for a nerve-damage condition of the cornea (the clear front of the eye). Results were mixed. No real human study of the 7-amino-acid piece was found. One entry on the US trials registry names TB-500. It was posted in 2026. It calls itself a fictional example, so it does not count as a trial. The effects and side effects of TB-500 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 reason for mixing them is only an idea. It has not been shown to work. In animal and lab studies, BPC-157 was mostly linked to the growth of new blood vessels. It was also linked to nitric oxide, a signal chemical in the body. Thymosin β4, the protein TB-500 comes from, was linked to how cells move into a wound. The idea is that two peptides working on different parts of healing might add up.
This idea has been tested once, in rats. A 2026 study used 32 rats with repaired Achilles tendons. It compared each peptide alone with the two together. The mix did no better than either peptide alone. No clinical trial has tested the mix in people. The only human reports found are a small clinic chart review with no comparison group, and one side-effect 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 that combines them. No regulator has looked at the mix at all. FDA decisions cover each peptide on its own.
Pharmacy mixing (compounding): in September 2023, the FDA put each peptide in Category 2. It reviewed each one separately. Category 2 is the group the FDA said raises significant safety risks. Pharmacies making products with them could face FDA action. By April 2026, the FDA page listed both as withdrawn from that group by the people who had proposed them. In July 2026, an FDA advisory panel voted narrowly in favour of allowing each peptide. The vote was for 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. In October 2026 the US health department (HHS) published a draft policy easing enforcement for single-ingredient BPC-157 and TB-500 products made by licensed pharmacies under set conditions. It does not cover blends, and it is not FDA approval.
Sport: the World Anti-Doping Agency bans both peptides at all times. So any product that contains them is banned 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. HHS’s draft enforcement-discretion policy of 2026-10-30 (docket HHS-OASH-2026-0496) covers single-active-ingredient products only, so a two-peptide product falls outside it regardless of the status of each component. 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.
