TB-500 vs BPC-157: two healing peptides compared

TB-500 is not what you think it is

Many websites use TB-500 and thymosin beta-4 as if they were the same thing (FDA 2026). Thymosin beta-4 is a 43 amino acid protein made by many cell types in the body (FDA 2026). But the two are not the same molecule.

In 2012, a doping lab analysed a product called TB-500 and found it contained only a 7 amino acid fragment of thymosin beta-4: Ac-LKKTETQ, residues 17 to 23 (Esposito et al. 2012). FDA's 2026 review defines TB-500 the same way: the acetylated fragment, not the full protein (FDA 2026). WADA prohibits "Thymosin-β4 and its derivatives e.g. TB-500" at all times under S2.3 (FDA 2026).

This matters because the fragment has never been tested on its own in people. FDA states: "no articles were found in which TB-500 was administered to humans" (FDA 2026). The only published exposure since then is 3 dental patients who got a product labelled TB-500 mixed with four other drugs (Froum et al. 2026).

The trials quoted online all used full-length thymosin beta-4, a different and much larger molecule, and most tested eye drops, not injections (ARISE-2, ARISE-3). What is actually in a vial may not match the label: lab analysis of products sold as TB500 and TB1000 found their contents were "not systematically consistent" with their described content (Delcourt et al. 2023).

What the thymosin beta-4 trials actually show

About 2,190 people have been enrolled, placebo groups included, in 16 randomised controlled trials of full-length thymosin beta-4 (ARISE-2, ARISE-3, Ruff et al. 2010, among others). Roughly 80% of the enrolment was in eye-drop trials.

Eye drops (about 1,730 enrolled). The ARISE program tested thymosin beta-4 drops for dry eye in three trials. ARISE-2 (601 enrolled) and ARISE-3 (700 enrolled) posted results showing the drops performed about the same as placebo (ARISE-2, ARISE-3). A smaller trial in neurotrophic keratopathy stopped early at 18 patients: 6 of 10 healed on thymosin beta-4 versus 1 of 8 on placebo at 4 weeks, but this missed statistical significance with p = 0.066 (Sosne et al. 2022).

Topical gel (about 180 enrolled). A phase 2 trial of 73 patients with venous leg ulcers at 8 European sites found safety similar to placebo. The 0.03% dose "may" speed healing, but no significant primary efficacy was claimed (Guarnera et al. 2010).

IV injection (about 280 enrolled, placebo included; the only injected trials). A phase 1 trial of IV thymosin beta-4 in 40 healthy volunteers found no serious adverse events over 14 days (Ruff et al. 2010). A Chinese phase 1 enrolled 84 healthy volunteers, some on placebo, with no dose-limiting toxicity (Wang et al. 2021). The one published heart attack trial randomised 96 patients to IV thymosin beta-4 or placebo: overall infarct size at 90 days was not significantly different from placebo (Zhang et al. 2025). A subgroup of 43 patients dosed within 8 hours did better, but subgroup findings need confirming in a larger trial.

Nobody has studied either form by subcutaneous or intramuscular injection. Nobody has tested either for a tendon, ligament or muscle injury in humans.

TB-500 and BPC-157 side by side

BPC-157 is a synthetic 15 amino acid peptide based on a fragment of a protein from human gastric juice. In our PubMed count (3 November 2026), Predrag Sikirić of the University of Zagreb is an author on about 75% of BPC-157 papers (176 of 236).

About 84 people have received BPC-157 in published reports (FDA 2026, Froum et al. 2026). Most got it as a rectal enema in two placebo-controlled studies that exist only as meeting abstracts (FDA 2026). The one controlled trial testing a disease (ulcerative colitis, 2 weeks, about 53 people randomised) found the difference from placebo was 1.6 points on a disease activity index, with a 95% confidence interval of −4.84 to 1.62: not statistically significant (FDA 2026).

The published clinical reports are small and uncontrolled: 17 knee patients, 16 reached by phone months later, 4 of whom had also got thymosin beta-4, with no comparison group (Lee and Padgett 2021), 12 women with bladder wall injections and no control (Lee, Walker and Ayadi 2024), 2 people in an IV safety pilot (Lee and Burgess 2025), and 3 dental nerve injury patients who got BPC-157 mixed with TB-500 and three other drugs (Froum et al. 2026). A systematic review found 35 preclinical studies and 1 clinical study for musculoskeletal use: the uncontrolled knee chart review (Vasireddi et al. 2025).

Neither is approved

Neither is an approved medicine in the US or the EU. FDA found no approval for BPC-157 in any country, and none for TB-500 in the countries it checked (FDA 2026, TB-500, FDA 2026, BPC-157).

Both had been in FDA's Category 2 (substances that may present significant safety risks for compounding). By April 2026 both were listed as "nominated but withdrawn" (FDA Category 2). FDA scientists recommended against adding either to the compounding bulks list (FDA 2026, TB-500, FDA 2026, BPC-157). In October 2026, HHS announced a draft policy not to act against pharmacies compounding certain peptides (HHS 2026).

Both are prohibited at all times by WADA: TB-500 under S2.3 and BPC-157 under S0 (FDA 2026, TB-500, FDA 2026, BPC-157).

Doses used in studies

These are the doses researchers used in their trials.

Full-length thymosin beta-4: IV synthetic 42 to 1,260 mg daily for up to 14 days in healthy volunteers (Ruff et al. 2010). IV recombinant 0.05 to 25 micrograms per kg single dose, then 0.5 to 5 micrograms per kg daily for 10 days (Wang et al. 2021). Eye drops: 0.1% solution (Sosne et al. 2022). Topical gel: several strengths in a dose-escalation trial, with 0.03% the one that "may" speed healing (Guarnera et al. 2010). No human dose exists for the TB-500 fragment or for subcutaneous injection of any form.

BPC-157: rectal enema at 0.25 to 2 mg per kg, one dose and then daily for 7 days, in healthy volunteers; in a separate trial, 80 mg daily for 2 weeks in ulcerative colitis (FDA 2026). Intra-articular: 2 to 4 mg per knee injection (Lee and Padgett 2021). No published human data exist for subcutaneous, oral or nasal BPC-157.

Safety: not much to go on

In the two IV phase 1 trials (124 healthy volunteers, placebo included, up to 14 days), adverse events were infrequent and mild or moderate, with no serious adverse events (Ruff et al. 2010, Wang et al. 2021). The TB-500 fragment has no human safety data at any dose (FDA 2026).

For BPC-157, no serious adverse events were reported in the roughly 84 people dosed, but FDA notes safety monitoring was unclear in most studies (FDA 2026). FDA's adverse event database held three reports for injected products: injection site reaction, shortness of breath requiring an emergency room visit, and diffuse skin and gum hyperpigmentation that returned when the person restarted a BPC-157 and TB-500 product (FDA 2026).

FDA flags immunogenicity risk for both peptides, especially from aggregates and impurities in compounded products (FDA 2026, TB-500, FDA 2026, BPC-157). In lab and tumour tissue studies, higher thymosin beta-4 levels are linked to colorectal cancer invasion and spread (Wang et al. 2004, Huang et al. 2007). FDA notes that researchers think BPC-157 may work partly by growing new blood vessels, and that no carcinogenicity studies exist (FDA 2026). Whether that could feed a tumour has not been tested. Neither concern has been shown in people who received these peptides.

What this adds up to

Two peptides, almost no relevant human data. The TB-500 fragment that people buy has no human study of its own. Full-length thymosin beta-4 has real trial data, but the biggest trials tested eye drops for dry eye and they failed. BPC-157 has reached about 84 people in published reports, mostly through enemas that never made it past meeting abstracts. Neither peptide has a completed human trial for the thing people buy them for: recovering from an injury.

Sources

1. FDA 2026, PCAC briefing document on TB-500. FDA staff evaluation for the Pharmacy Compounding Advisory Committee, July 2026.
2. FDA 2026, PCAC briefing document on BPC-157. FDA staff evaluation for the Pharmacy Compounding Advisory Committee, July 2026.
3. Froum et al. 2026, BPC-157 in dental nerve injury. Three case reports, BPC-157 mixed with TB-500 and three other drugs.
4. Vasireddi et al. 2025, systematic review of BPC-157 for musculoskeletal injuries. 35 preclinical and 1 clinical study identified to June 2024.
5. Esposito et al. 2012, acetylated fragment 17 to 23 of thymosin beta-4 identified in TB-500. Doping-lab analysis of a product called TB-500.
6. Delcourt et al. 2023, TB500 and TB1000 product analysis. Lab analysis of online products labelled TB500 and TB1000.
7. ARISE-2, RGN-259 eye drops in dry eye. Phase 3 RCT, 601 enrolled, results posted.
8. ARISE-3, RGN-259 eye drops in dry eye. Phase 3 RCT, 700 enrolled, results posted.
9. Ruff et al. 2010, IV thymosin beta-4 phase 1. Randomised phase 1 in 40 healthy volunteers.
10. Sosne et al. 2022, RGN-259 in neurotrophic keratopathy (SEER-1). Phase 3 RCT, 18 patients, stopped early.
11. Guarnera et al. 2010, topical thymosin beta-4 in venous ulcers. Phase 2 dose-escalation RCT, 73 patients, 8 European sites.
12. Wang et al. 2021, recombinant thymosin beta-4 (NL005) phase 1. Randomised phase 1 in 84 healthy Chinese volunteers.
13. Zhang et al. 2025, NL005 phase IIb in heart attack. Double-blind RCT, 96 patients, 14 Chinese centres.
14. Lee and Padgett 2021, intra-articular BPC-157 in knee pain. Retrospective chart review and phone survey, 17 treated, one Florida clinic.
15. Lee, Walker and Ayadi 2024, BPC-157 bladder wall injection. Single-arm pilot, 12 women with interstitial cystitis.
16. Lee and Burgess 2025, IV BPC-157 safety pilot. Two patients, open-label.
17. FDA Category 2 list, bulk drug substances that may present significant safety risks. TB-500 and BPC-157 under "nominated but withdrawn," page current as of April 2026.
18. HHS 2026, draft enforcement discretion policy. Federal Register document 2026-22192, October 2026.
19. Wang et al. 2004, thymosin beta-4 in colorectal cancer invasion and liver metastasis. Laboratory study of colon cancer cells and matched patient tumours.
20. Huang et al. 2007, thymosin beta-4 and epithelial-mesenchymal transition in colon cancer cells. Laboratory study of colon cancer cells forced to overexpress thymosin beta-4.