Dr. Pep

Learn · October 27, 2026

TB-500 doses in studies: what researchers actually used

No human study of TB-500 itself has been published, so there is no human dose from a TB-500 study to point to.[1] The only controlled animal healing study of TB-500 in our records used 60 µg/kg/day in rats.[2] The human dose data come from full-length thymosin beta-4, a different and much larger molecule.[3]

TB-500 is not the same as thymosin beta-4

This point matters for every dose below. Thymosin beta-4 (Tβ4) is a 43-amino-acid protein the body makes. TB-500 is a synthetic, N-acetylated 7-amino-acid fragment of it.[4][5][3]

Most human trials tested full-length thymosin beta-4, such as RGN-259 eye drops, RGN-352 IV, recombinant NL005 and a topical gel for venous ulcers. Their results do not show that TB-500 works or is safe.[6][7][8][9][3]

What was used in animals

  • In a rat study, 32 rats (8 per group) had the Achilles tendon cut and repaired. TB-500 was given at 60 µg/kg/day intraperitoneally for 4 weeks.[2]
  • Treated rats had higher load to failure and better tendon scores than controls (p < 0.05).[2]
  • This is the only controlled in-animal healing study of TB-500 in the records we hold.[2]
  • FDA's reviewers found no animal studies that tested TB-500 for wound healing in vivo.[1]
  • In a cell study they found, TB-500 at 50 µg/mL did not close scratch wounds in fibroblast cultures.[1]
  • A 2025 paper put a TB500 peptide (LKKTETQ) into a hydrogel on burned corneas. The peptide was part of an engineered gel, so this does not describe injected TB-500.[10]

Doses in human studies of full-length thymosin beta-4

None of these used the TB-500 fragment. The routes and units differ between trials.[6][7][3]

  • Neurotrophic keratopathy, 18 people: 0.1% RGN-259 eye drops for 4 weeks. The sponsor's related SEER-1 trial used 5 times a day.[6]
  • Severe dry eye, 9 people: 0.1% RGN-259 eye drops 6 times a day for 28 days.[11]
  • Moderate-to-severe dry eye, 72 people: RGN-259 0.1% for 28 days.[12]
  • Venous leg ulcers, 73 people in a dose-escalation trial: a topical gel, where the 0.03% dose was described as possibly able to speed healing. Treatment length is not in the abstract.[9]
  • Healthy volunteers, IV: 42 to 1260 mg per dose, as a single dose and then daily for 14 days, in 4 cohorts of 10.[7]
  • Healthy Chinese volunteers, IV recombinant NL005: 54 people had a single dose of 0.05 to 25 µg/kg, and 30 people had 0.5 to 5 µg/kg daily for 10 days.[3]

What the safety reports showed

For full-length thymosin beta-4, the trials reported mostly mild to moderate adverse events. They were small groups followed for days to weeks. That is not long-term safety data and not data for the fragment.[7][3][6]

  • In the IV trial in healthy volunteers, adverse events were mild to moderate with no dose-limiting toxicity.[7]
  • In the NL005 trial, adverse events were mild to moderate only, with no serious adverse events.[3]
  • In the phase 3 eye-drop trial NCT03937882, instillation site pain was 6.6% on drug vs 4.6% on placebo. Serious adverse events were 0.0% on drug vs 0.0% on placebo.[13]
  • In NCT02974907, serious adverse events were 1.0% on drug vs 0.7% on placebo.[14]
  • FDA's reviewers found a lack of both clinical and nonclinical safety information for TB-500, and no toxicity studies.[1]

Seller doses are not study doses

You may see dosing claims online, such as 1 to 20 mg per week by injection. These are not from studies. They appear in an FDA warning letter quoting a seller's website.[15]

FDA's briefing document said it found no medical literature in which TB-500 was given to patients for any condition.[1]

Product identity is also uncertain. A lab analysis of products sold as TB500 or TB1000 found contents not consistently as labelled.[16]

The bottom line

The only controlled animal healing study of TB-500 in our records used 60 µg/kg/day intraperitoneally for 4 weeks, with 8 rats per group.[2] Human dosing data exist only for full-length thymosin beta-4, in trials with eye drops, gel and IV, and they do not transfer to the fragment.[6][7][3]

Our sources do not cover a studied human dose of TB-500. FDA's reviewers also found no toxicity studies for it.[1]

Sources

  1. 1.FDA document
  2. 2.Effects of BPC-157 and TB-500 on Achilles tendon healing in rats: A histopathological and biomechanical study. (Jt Dis Relat Surg, 2026)
  3. 3.A first-in-human, randomized, double-blind, single- and multiple-dose, phase I study of recombinant human thymosin β4 in healthy Chinese volunteers. (J Cell Mol Med, 2021)
  4. 4.Synthesis and characterization of the N-terminal acetylated 17-23 fragment of thymosin beta 4 identified in TB-500, a product suspected to possess doping potential. (Drug Test Anal, 2012)
  5. 5.Doping control analysis of TB-500, a synthetic version of an active region of thymosin β₄, in equine urine and plasma by liquid chromatography-mass spectrometry. (J Chromatogr A, 2012)
  6. 6.0.1% RGN-259 (Thymosin ß4) Ophthalmic Solution Promotes Healing and Improves Comfort in Neurotrophic Keratopathy Patients in a Randomized, Placebo-Controlled, Double-Masked Phase III Clinical Trial. (Int J Mol Sci, 2022)
  7. 7.A randomized, placebo-controlled, single and multiple dose study of intravenous thymosin beta4 in healthy volunteers. (Ann N Y Acad Sci, 2010)
  8. 8.ClinicalTrials.gov NCT01311518
  9. 9.The effect of thymosin treatment of venous ulcers. (Ann N Y Acad Sci, 2010)
  10. 10.Alkaline Phosphatase-Triggered Spatiotemporal Repair of Corneal Injury with TB500 Peptide Hydrogel. (ACS Appl Mater Interfaces, 2025)
  11. 11.Thymosin β4 significantly improves signs and symptoms of severe dry eye in a phase 2 randomized trial. (Cornea, 2015)
  12. 12.Thymosin beta 4 ophthalmic solution for dry eye: a randomized, placebo-controlled, Phase II clinical trial conducted using the controlled adverse environment (CAE™) model. (Clin Ophthalmol, 2015)
  13. 13.ClinicalTrials.gov NCT03937882
  14. 14.ClinicalTrials.gov NCT02974907
  15. 15.FDA: Warning Letter, Warrior Labz SARMS (2023-06-12), BPC-157, TB-500, thymosin beta-4, MK-677
  16. 16.TB500/TB1000 and SGF1000: A scientific approach for a better understanding of misbranded and adulterated drugs. (Drug Test Anal, 2023)

Written by Dr. Pep's research assistant from its source library and checked against those sources. Not medical advice. For adults 18+.