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Repair & recovery · Evidence tier A

Thymosin beta-4

Thymosin β4 · Tβ4 · TB4 · Timbetasin (US generic name) · RGN-259 (eye drops in trials) · RGN-137 (skin gel in trials)

Thymosin beta-4 is a natural protein sold for injury recovery, often confused with TB-500, a lab-made piece of it12. We found no trial of it on muscle or tendon injuries, and two large dry-eye trials found no clear benefit3456824.

Last reviewed · 54 sources · 32 min read · By the Pinc Peptide editors

Illustration: a glass vial with a pink label reading Thymosin beta-4
Illustration, not a real product: an empty glass vial (photo: Missouri Historical Society, public domain) with our label. See every vial.

Quick answers

What is it?
A natural protein of 43 amino acids found in many cell types and body fluids17. It binds actin, a protein cells use to keep their shape and move17. TB-500 is a lab-made copy of a 7-amino-acid piece of it1.
Does it work?
For injuries, untested: we found no trial of it on muscle, tendon or ligament injuries34. Its eye drops showed no clear benefit over placebo in two large dry-eye trials56824. Small trials of a skin gel for ulcers did not show a clear benefit either91011.
Is it safe?
Short trials found no serious side effects from IV doses in healthy volunteers, or from eye drops in a 700-person trial61213. We found no registered trial of injections under the skin or into muscle3. Its role in tumor growth is unsettled13.
Is it legal?
Not approved by FDA for any use1415. FDA treats it as a biological product, which US pharmacies may not make15. Banned in sport at all times16. In Australia it is prescription-only and illegal to hold without a prescription17.
What is in the vials?
Unknown. Finnrick, a testing service, publishes lab results for 34 products, including TB-500 but not thymosin beta-418. One seller’s ‘TB-500 (Thymosin Beta 4)’ page gives the full protein’s formula19. A German anti-doping lab found it among 337 black-market products20.

What it is

Thymosin beta-4 is a natural protein: a chain of 43 amino acids, the first of which carries a small chemical cap called an acetyl group721. It was first isolated from calf thymus tissue, but it is made by many cell types and found in blood, saliva, tears and wound fluid1. Inside cells it binds single molecules of actin, the protein that forms the cell’s internal scaffolding, and keeps them from joining into filaments7. FDA’s review says this appears essential to building and maintaining that scaffolding, which cells need to keep their shape and move1. A 2005 review described a key role in healing skin and corneal wounds and proposed uses in repairing ulcers and organs damaged by heart attack or stroke22. TB-500 is a different, lab-made molecule: a copy of positions 17 to 23 with its own acetyl cap, and FDA says the two ‘are not the same substance’1.

Its sequence was reported in 1981 from calf thymus, where it was one of several peptides in an extract called thymosin fraction 5 and was first studied as a possible thymus hormone121. Despite the shared name, thymosin alpha-1 is a different molecule: 28 amino acids from the front end of another protein, prothymosin alpha23. RegeneRx Biopharmaceuticals, based in Maryland, developed three drug forms: RGN-259 eye drops, the RGN-137 skin gel and the RGN-352 injection2425. The injection’s planned heart-attack trial was withdrawn before it started26, and a 2019 trial of the gel in epidermolysis bullosa, a rare skin disease, ended after 4 patients for a ‘Business Decision’2427. ReGenTree, a joint venture of RegeneRx and HLB Therapeutics, runs the eye-drop trials625. In China, a version made by genetic engineering, NL005 from Beijing Northland Biotech, has been given by IV to healthy volunteers and to heart-attack patients132829. Its trial report describes it as 44 amino acids long, while the natural protein has 43713.

Benefits: what the research shows

This entry’s tier A means only that two large trials were completed, both of eye drops for dry eye in 601 and 700 adults; neither showed a clear benefit, and the rating says nothing in favor of injury healing56. We found no registered or published trial of thymosin beta-4 in muscle, tendon or ligament injuries: a ClinicalTrials.gov search on 8 October 2026 returned 30 records, of which we counted 20 as studies of thymosin beta-4 (2 of them withdrawn before starting), none in those injuries, and a PubMed search found no clinical trial34. In ARISE-3, the main measures at day 15 barely differed between drops and placebo6, and the company said the trial ‘did not meet its primary outcome measures’ but reported that one symptom, grittiness, improved8. In ARISE-2, discomfort at day 29 was no better on the drops than on placebo, and the company said the trial did not repeat the results of an earlier one524. Two smaller dry-eye trials gave mixed results: in 72 people, neither main measure differed significantly from placebo32, while in 9 people with severe dry eye the authors reported significant improvements in symptoms and signs33. In neurotrophic keratopathy, a nerve-damage disease of the cornea, a trial stopped for business reasons after 18 patients; at 4 weeks, its main measure, the defect had healed completely in 6 of 10 on the drops and 1 of 8 on placebo, short of statistical significance, and two weeks after treatment ended in 5 of 10 and 0 of 8, a significant difference3435. A European trial of the same use (SEER-3) missed its main goal in 2025, with what HLB Therapeutics, RegeneRx’s partner, called ‘abnormally high efficacy’ in the placebo group36. Another (SEER-2) has finished treating and following patients: in June 2025 HLB Therapeutics aimed for top-line data by the end of that year, and in an announcement RegeneRx reproduced on 1 September 2026, it said the contract research organization managing the trial had proposed mid-November 2026 for submitting them2536. Skin-gel trials saw complete healing of pressure ulcers in 8 of 54 people on the gel and 3 of 18 on placebo, and of leg ulcers in a similar share of each group; in epidermolysis bullosa, a group of mostly inherited blistering skin diseases, wounds healed in 8 of 22 on the gel and 5 of 8 on placebo in a trial stopped early for lack of patients and expired drug91037. IV safety trials in healthy volunteers found no dose-limiting toxicity or serious adverse event: a US study of 40 people given synthetic thymosin beta-4 or placebo, and Chinese studies that gave a recombinant version, NL005, once to 44 people and daily for 10 days to 24, with 10 and 6 more on placebo1213. In a 96-patient heart-attack trial of a recombinant form, damaged heart muscle was significantly smaller than on placebo only in a subgroup whose treatment started early38. In a randomized study of 71 people with seborrheic dermatitis, a scaly scalp condition, the authors reported that 4 weeks of a gel of the recombinant protein worked better than ketoconazole, an antifungal lotion, and that its effect was sustained39. A chart review from a Florida clinic said 75% of the 4 knee-pain patients given BPC-157 with ‘TB4’ injected into the knee showed significant improvement; there was no comparison group40. None of this is evidence for TB-500, a different molecule1. The healing claims rest on animal studies. Thymosin beta-4 applied to skin wounds, or injected into the abdomen, sped healing in rats41, and applied to wounds it sped healing in diabetic and old mice42. In mice whose heart artery was tied off, it improved heart function43. In rats with a cut knee ligament, 1 µg placed in the gap gave more orderly and stronger healing tissue at 4 weeks44. Injured mouse muscle made more of its own thymosin beta-4, and in lab dishes the protein drew in muscle-forming cells45. None of these studies tested it in people with injuries.

Key human studies

StudyDesignPeopleDose and routeResult
ReGenTree, ARISE-3 (results posted on ClinicalTrials.gov, 2026)6NCT03937882 Phase 3, randomized, quadruple-masked, placebo-controlled trial in adults with dry eye at 20 US sites, using a controlled-environment chamber to provoke symptoms 700 0.1% RGN-259 eye drops in both eyes four times a day for 14 days, or placebo drops Main measures at day 15 were nearly identical: the main staining score fell 0.41 points on the drops and 0.46 on placebo (0 to 4 scale), and discomfort fell 0.4 in both groups (0 to 5 scale); no statistical test was posted6. The company said the trial ‘did not meet its primary outcome measures’ but that grittiness improved8. No serious adverse events in either group6.
ReGenTree, ARISE-2 (results posted on ClinicalTrials.gov, 2022)5NCT02974907 Phase 3, randomized, quadruple-masked, placebo-controlled trial in adults with dry eye 601 0.1% RGN-259 eye drops four times a day for 28 days, or placebo drops At day 29, discomfort rose 0.07 points on the drops and fell 0.04 on placebo (0 to 5 scale), and staining, measured in 218 people, rose 0.07 and fell 0.01 (0 to 4 scale); no statistical test was posted5. The company reported less discomfort at day 15 (p = 0.0149) and less staining in a subgroup, but said the trial ‘was not successful in duplicating the results’ of ARISE-124. Serious adverse events: 3 of 299 on the drops and 2 of 302 on placebo5.
Zhang et al., Cardiovasc Res 202538PubMed · DOI Randomized, placebo-controlled, double-blind trial in patients with ST-elevation heart attack after a procedure to reopen the artery, reported with mouse and cell studies 96 Recombinant human thymosin beta-4; dose, route and trial registration not stated in the abstract The infarcted area did not differ significantly from placebo overall; at the 90-day follow-up it was significantly smaller in the group given the first dose within 8 hours of the procedure (n = 43 in the abstract)38.
Guarnera et al., Ann N Y Acad Sci 201011PubMed · DOI · NCT00832091 Phase 2, randomized, double-blind, placebo-controlled, dose-escalation trial in venous leg ulcers at eight sites in Italy and Poland 73 RGN-137 gel at 0.01%, 0.03% or 0.1% on the ulcer once a day for up to 84 days, or placebo gel Ulcers healed completely in 12 of 55 people on the gel and 4 of 17 on placebo; the registry lists 72 participants9. The authors judged safety ‘comparable to placebo’ and said 0.03% ‘may have the potential to accelerate wound healing’11.
Ruff et al., Ann N Y Acad Sci 201012PubMed · DOI Randomized, placebo-controlled, single and multiple ascending-dose safety study in healthy volunteers 40 Synthetic thymosin beta-4 by IV at 42, 140, 420 or 1,260 mg, once and then daily for 14 days (four cohorts of 10) Adverse events were infrequent and mild or moderate, with no dose-limiting toxicity or serious adverse event; the half-life grew longer as the dose rose12.
Sosne et al., Int J Mol Sci 2022 (SEER-1)35PubMed · DOI · NCT02600429 Phase 3, randomized, placebo-controlled, double-masked trial in neurotrophic keratopathy, stopped early for a business decision 18 0.1% RGN-259 eye drops five times a day for 4 weeks, or placebo drops Complete healing at 4 weeks, the main measure, in 6 of 10 on the drops and 1 of 8 on placebo (p = 0.0656), and at day 43, two weeks after treatment ended, in 5 of 10 and 0 of 8 (p = 0.0359)35. The authors observed no significant adverse effects; serious adverse events: 1 of 10 vs 0 of 83435.

Doses studied

Doses below are what studies used or what a label says. They are not advice, and gray-market products may not contain what their label says.

In human studies

Eye drops: 0.1% four times a day for 14 days (ARISE-3) or 28 days (ARISE-2), five times a day for 4 weeks (SEER-1), twice a day for 28 days (a dry-eye chamber trial) and six times a day for 28 days (severe dry eye)56333454. Skin gels: 0.01%, 0.03% or 0.1% once a day for up to 84 days (leg ulcers) or up to 56 days (epidermolysis bullosa), and 0.01%, 0.02% or 0.1% for up to 84 days (pressure ulcers)91037. IV: 42, 140, 420 or 1,260 mg once and then daily for 14 days in healthy volunteers12; the recombinant NL005 at 0.05 to 25.0 µg/kg once, or 0.5, 2.0 or 5.0 µg/kg daily for 10 days, in healthy volunteers13, and at 0.25 to 2.0 µg/kg daily for 7 days in heart-attack patients2829. None of these doses applies to TB-500, a different molecule1.

In animal studies

Mice (skin wounds): 50 µL of 0.1% thymosin beta-4 in buffered saline or 0.05% in a hydrogel on each wound, on the day of wounding and 48 hours later, in 26-month-old mice, as described in FDA’s review1. Rats (knee ligament): 1 µg in 100 µL of fibrin sealant placed in the gap of the cut ligament at surgery44.

What users report

No community dosing page was cited for this compound.

Half-life
0.5 to 2.08 hours after an IV dose (recombinant version, healthy volunteers)13In the Chinese trial of NL005, blood levels peaked 3 to 15 minutes after an IV dose, and the authors say the half-life matched reports on chemically made thymosin beta-413. In the earlier US trial of much larger IV doses, the half-life grew longer as the dose rose12. We found no registered trial that measured it after injection under the skin or into muscle3.
Routes
  • Eye drops (human trials in dry eye and corneal disease)
  • Gel on skin wounds (human trials in ulcers and epidermolysis bullosa)
  • IV injection (healthy volunteers and heart-attack trials)
  • Knee-joint injection with BPC-157 (4 patients in one chart review)
  • Injection under the skin or into muscle (no human data found)

Every dose studied for Thymosin beta-4, with sources →

Quality and the gray market

What testing finds

No public test of a product sold as thymosin beta-4 was found: it is not among the 34 products in Finnrick’s published lab results, and Finnrick’s TB-500 results are covered on the TB-500 page18. One online seller’s page for ‘TB-500 (Thymosin Beta 4)’ gives the full 43-amino-acid sequence, the formula C212H350N56O78S and a molecular weight of 4963 g/mol, which describe the full protein, not the 7-amino-acid fragment FDA calls TB-500119. The Cologne anti-doping laboratory in Germany found thymosin beta-4 among 337 black-market products it analyzed from 2010 to 201320. A 2025 equine anti-doping study showed that a non-natural impurity from manufacturing could be detected in a horse’s blood plasma after a single dose of a thymosin beta-4 product52. The outsourcing facility FDA warned in 2026 for making thymosin beta-4 had recalled its sterile products in July 2025 for ‘lack of sterility assurance or microbial contamination’; the letter does not say whether its thymosin beta-4 was among them15.

How it is sold

FDA notes that several websites call TB-500 a synthetic version of thymosin beta-4 and often use the two names interchangeably1. One clinic site FDA’s review cites, a Phoenix-area functional-medicine clinic, offers ‘Thymosin Beta 4 (TB-500) Peptide Therapy’, says it supports ‘healing of muscle, tendon, ligament, and skin’, calls TB-500 ‘the synthetic analog used clinically’ and says it uses ‘high-quality, compounded peptides’ (checked 8 October 2026)12. An online seller lists ‘TB-500 (Thymosin Beta 4)’ as 5 or 10 mg of powder at $78.00 to $140.00, ‘sold for laboratory research use only’ and ‘not for human consumption’ (checked 8 October 2026)19. FDA’s 2026 letter shows that a registered US outsourcing facility made thymosin beta-4 products15, and Health Canada’s April 2025 warning about peptides seized from a Calgary wellness center listed one as ‘Thymosin-β4 (TB4 or TB-500)’51.

Side effects and risks

  • Untested for the uses it is sold for: we found no trial of it in injuries and no registered trial that injected it under the skin or into muscle; the only human report near those uses that we found is a chart review of 4 knee-pain patients, with no comparison group3440.
  • Short-term data only: trials that report their dosing gave it by IV for at most 14 days and as a skin gel for up to 84 days, so the effects of longer use are unknown91012.
  • Cancer question: the authors of a 2021 trial note research suggesting it can promote tumor spread by encouraging blood-vessel growth and the movement of epithelial cells, and other studies suggesting an anti-tumor effect; they reported no tumor-related adverse events in their trial of up to 10 days13. A blood tumor marker (SCC), which they describe as low in sensitivity and specificity, rose mildly and briefly: after single doses, an abnormal reading was logged as an adverse event 8 times among the 44 people given NL005, 6 of them at the two highest doses, and never among the 10 on placebo; after 10 daily doses, 4 times among 24 on NL005 and twice among 6 on placebo13. The authors said the rise followed the drug’s level in the blood, which they linked to thymosin beta-4 promoting the regrowth of epithelial cells, and that all readings returned to normal13.
  • Antibodies: in that trial, 1 of 108 samples after single doses and 2 of 56 samples after repeated doses tested positive for antibodies against the drug; all were negative at follow-up, and the authors suggest the positive readings reflected a systematic testing error13.
  • Eye drops: in the 700-person dry-eye trial, pain on putting the drops in was reported by 23 of 350 people on the drops and 16 of 349 on placebo, and reduced sharpness of vision by 12 and 7; no one had a serious adverse event6.
  • Mix-ups: sellers use ‘TB-500’ and ‘thymosin beta-4’ for each other, so a product’s name does not say which molecule it is meant to contain119.
  • Unapproved injectables: Health Canada warns they can cause infection and allergic reactions51, and the US facility FDA warned for making thymosin beta-4 had recalled its sterile products over ‘lack of sterility assurance or microbial contamination’15.
  • Sport and the law: it is banned at all times under the anti-doping code, and a horse-racing study shows that a manufacturing impurity can reveal a dose1652. In Australia, holding it without authority is illegal17.

Questions people ask

Is thymosin beta-4 FDA approved?

No. FDA has approved no product containing it, and RGN-259 eye drops are still in trials1425. In a 2026 warning letter, FDA called thymosin beta-4 made by an outsourcing facility an unapproved new drug and a biological product with no approved license15.

Can compounding pharmacies make thymosin beta-4?

No. FDA treats it as a biological product, and biological products are not eligible for the exemptions that let US pharmacies and outsourcing facilities compound drugs15. FDA’s July 2026 advisory committee considered TB-500, not thymosin beta-450.

Thymosin beta-4 vs TB-500: what’s the difference?

Thymosin beta-4 is the natural 43-amino-acid protein, while TB-500 is a lab-made copy of 7 of its amino acids with an acetyl cap, and FDA says the two ‘are not the same substance’1. Thymosin beta-4 has been tested in people as eye drops, skin gels and IV doses; FDA found no study that gave TB-500 to people13.

What is RGN-259?

RGN-259 is an eye drop containing 0.1% thymosin beta-4, tested for dry eye and for neurotrophic keratopathy, a nerve-damage disease of the cornea634. Two large dry-eye trials showed no clear benefit over placebo56824. For a trial in that eye disease (SEER-2), the contract research organization managing it has proposed mid-November 2026 as the target for top-line results25. It is not approved14.

Is thymosin beta-4 banned in sports?

Yes. The World Anti-Doping Agency’s list bans ‘Thymosin-ß4 and its derivatives e.g. TB-500’ at all times, and the 2027 list keeps it1648. In January 2016 the Court of Arbitration for Sport banned 34 Essendon players in Australian football for two years from 31 March 2015, with credit for time already served, so most of the bans ended in November 2016; the case concerned thymosin beta-4 in the club’s 2012 supplements program53.

Does thymosin beta-4 cause cancer?

It is not known. Research points both ways: the authors of a 2021 trial note studies suggesting it can promote tumor spread and others suggesting an anti-tumor effect13. Their trial, which gave it by IV for up to 10 days, reported no tumor-related side effects, although a blood tumor marker rose mildly and briefly, most often at the two highest single doses13.

What is still unknown

  • What products sold as thymosin beta-4 actually contain: the full 43-amino-acid protein, the 7-amino-acid TB-500 fragment or something else. No public lab test of a product sold under the thymosin beta-4 name was found.
  • What the SEER-2 eye-drop trial found. The contract research organization managing it proposed mid-November 2026 for top-line results, after HLB Therapeutics had aimed for the end of 2025, and its registry record still said recruiting on 8 October 2026.
  • Whether ARISE-2 and ARISE-3 differ from placebo by a formal statistical test: the registry posts averages but no analysis, and neither trial was found in PubMed.
  • How many patients the European SEER-3 trial enrolled and where it is registered; the company letter gives neither.
  • Whether thymosin beta-4 raises the risk of cancer over months or years of use.
  • How the body absorbs and clears it after injection under the skin or into muscle, the routes sellers’ products imply; we found it measured only after IV doses.
  • Which product, dose, route and trial registration the 96-patient heart-attack trial used, and whether it was NL005.
  • Why the NL005 trial report gives 44 amino acids when the natural protein has 43.
  • Which high dose the NL005 phase 2b trial (NCT05984134) used: its arm description says 1.0 µg/kg and its intervention description 1.5 µg/kg.
  • Whether ‘TB4’ in the 2021 knee-pain chart review was full-length thymosin beta-4 or TB-500.
  • Why the leg-ulcer trial lists 72 participants in its registry record and 73 in the published paper.
  • Which registry record, if any, matches the published US IV safety study: a RegeneRx record with the same four doses (NCT00743769) says it was withdrawn before starting.
  • Its legal status in the UK and the European Union, which we did not verify.

Sources

  1. 1FDA Briefing Document, Pharmacy Compounding Advisory Committee meeting of July 23-24, 2026: TB-500-related bulk drug substances U.S. Food and Drug Administration, 15 May 2026. fda.gov
  2. 2Thymosin Beta 4 for Healing and Recovery Transformyou (clinic), accessed 8 Oct 2026. transformyou.com (seller page, deliberately not linked)
  3. 3ClinicalTrials.gov search: thymosin beta 4, timbetasin, Tb4, RGN-259, RGN-137, RGN-352 or NL005 (30 records; 20 test thymosin beta-4, none in muscle, tendon or ligament injuries) ClinicalTrials.gov, accessed 8 Oct 2026. clinicaltrials.gov
  4. 4PubMed search: thymosin beta-4 with tendon, ligament, muscle or sports injuries (13 results, none a clinical trial) National Library of Medicine (PubMed), accessed 8 Oct 2026. pubmed.ncbi.nlm.nih.gov
  5. 5Assessment of the Safety and Efficacy of RGN-259 Ophthalmic Solutions for Dry Eye Syndrome: ARISE-2 (NCT02974907) ClinicalTrials.gov, 5 Jan 2022. clinicaltrials.gov
  6. 6Assessment of the Safety and Efficacy of RGN-259 Ophthalmic Solutions for Dry Eye Syndrome: ARISE-3, NCT03937882 ClinicalTrials.gov, 28 Aug 2026. clinicaltrials.gov
  7. 7TYB4_HUMAN (P62328): Thymosin beta-4 UniProt Consortium, 2 Sep 2026. uniprot.org
  8. 8RegeneRx Reports Topline Results of ARISE-3 Dry Eye Trial RegeneRx Biopharmaceuticals (PR Newswire), 18 Mar 2021. prnewswire.com
  9. 9Study of Thymosin Beta 4 in Patients With Venous Stasis Ulcers (NCT00832091) ClinicalTrials.gov, 30 Mar 2010. clinicaltrials.gov
  10. 10Study of Thymosin Beta 4 in Patients With Pressure Ulcers (NCT00382174) ClinicalTrials.gov, 1 Feb 2010. clinicaltrials.gov
  11. 11The effect of thymosin treatment of venous ulcers Annals of the New York Academy of Sciences, Apr 2010. pubmed.ncbi.nlm.nih.gov
  12. 12A randomized, placebo-controlled, single and multiple dose study of intravenous thymosin beta4 in healthy volunteers Annals of the New York Academy of Sciences, Apr 2010. pubmed.ncbi.nlm.nih.gov
  13. 13A first-in-human, randomized, double-blind, single- and multiple-dose, phase I study of recombinant human thymosin β4 in healthy Chinese volunteers Journal of Cellular and Molecular Medicine, Sep 2021. pmc.ncbi.nlm.nih.gov
  14. 14Drugs@FDA via openFDA: search for active ingredient thymosin or timbetasin (no matches) U.S. Food and Drug Administration (openFDA), 8 Oct 2026. api.fda.gov · data query
  15. 15Warning letter to GenoGenix LLC (MARCS-CMS 718739) U.S. Food and Drug Administration, 20 Jan 2026. fda.gov
  16. 16World Anti-Doping Code International Standard: Prohibited List 2026 World Anti-Doping Agency, 24 Sep 2025. wada-ama.org
  17. 17Therapeutic Goods (Poisons Standard—October 2026) Instrument 2026 (F2026L01327) Federal Register of Legislation, Australian Government, 28 Sep 2026. legislation.gov.au
  18. 18Finnrick public data summary (llms-full.txt, generated 25 September 2026) Finnrick, 25 Sep 2026. finnrick.com
  19. 19TB-500 (Thymosin Beta 4) – 5MG / 10MG product page Core Peptides (vendor), accessed 8 Oct 2026. corepeptides.com (seller page, deliberately not linked)
  20. 20Identification of black market products and potential doping agents in Germany 2010-2013 European Journal of Clinical Pharmacology, Nov 2014. pubmed.ncbi.nlm.nih.gov
  21. 21Complete amino acid sequence of bovine thymosin beta 4: a thymic hormone that induces terminal deoxynucleotidyl transferase activity in thymocyte populations Proceedings of the National Academy of Sciences, Feb 1981. pubmed.ncbi.nlm.nih.gov
  22. 22Thymosin beta4: actin-sequestering protein moonlights to repair injured tissues Trends in Molecular Medicine, Sep 2005. pubmed.ncbi.nlm.nih.gov
  23. 23UniProtKB P06454: Prothymosin alpha (human), with the thymosin alpha-1 peptide at residues 2 to 29 UniProt Consortium, 2 Sep 2026. uniprot.org
  24. 24RegeneRx JV Announces Results of ARISE-2 Dry Eye Trial RegeneRx Biopharmaceuticals, 31 Oct 2017. regenerx.com
  25. 25Letter to stockholders: SEER-2 Phase 3 trial update RegeneRx Biopharmaceuticals, 1 Sep 2026. regenerx.com
  26. 26A Study of the Safety and Efficacy of Injectable Thymosin Beta 4 for Treating Acute Myocardial Infarction (NCT01311518) ClinicalTrials.gov, 22 Sep 2021. clinicaltrials.gov
  27. 27Evaluation of the Safety and Efficacy Study of RGN-137 Topical Gel for Junctional and Dystrophic Epidermolysis Bullosa (NCT03578029) ClinicalTrials.gov, 22 Aug 2022. clinicaltrials.gov
  28. 28Safety and Efficacy Study of Thymosin Beta 4 in Patients With Acute Myocardial Infarction (NCT05485818) ClinicalTrials.gov, 3 Aug 2022. clinicaltrials.gov
  29. 29Efficacy and Safety Study of Thymosin Beta 4 in Patients With Acute Myocardial Infarction (NCT05984134) ClinicalTrials.gov, 21 Jun 2024. clinicaltrials.gov
  30. 30Timbetasin, CID 16132341 PubChem, U.S. National Library of Medicine, accessed 8 Oct 2026. pubchem.ncbi.nlm.nih.gov
  31. 3121 CFR 600.3, Definitions (eCFR, as of 25 September 2026) Electronic Code of Federal Regulations (eCFR), 25 Sep 2026. ecfr.gov
  32. 32Thymosin beta 4 ophthalmic solution for dry eye: a randomized, placebo-controlled, Phase II clinical trial conducted using the controlled adverse environment (CAE™) model Clinical Ophthalmology, 2015. pubmed.ncbi.nlm.nih.gov
  33. 33Thymosin β4 significantly improves signs and symptoms of severe dry eye in a phase 2 randomized trial Cornea, May 2015. pubmed.ncbi.nlm.nih.gov
  34. 34Assessment of the Safety and Efficacy Study of RGN-259 Ophthalmic Solutions for Neurotrophic Keratopathy: SEER-1 (NCT02600429) ClinicalTrials.gov, 30 Aug 2023. clinicaltrials.gov
  35. 350.1% 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 International Journal of Molecular Sciences, 29 Dec 2022. pubmed.ncbi.nlm.nih.gov
  36. 36Letter to stockholders: SEER-3 top-line results RegeneRx Biopharmaceuticals, 24 Jun 2025. regenerx.com
  37. 37A Phase 2 Study on Effect of Thymosin Beta 4 on Wound Healing in Patients With Epidermolysis Bullosa (NCT00311766) ClinicalTrials.gov, 12 May 2014. clinicaltrials.gov
  38. 38Recombinant human thymosin beta 4 improves ischemic cardiac dysfunction in mice and patients with acute ST-segment elevation myocardial infarction after reperfusion Cardiovascular Research, 31 Dec 2025. pubmed.ncbi.nlm.nih.gov
  39. 39Recombinant human thymosin beta-4 (rhTβ4) improved scalp condition and microbiome homeostasis in seborrheic dermatitis Microbial Biotechnology, Sep 2021. pubmed.ncbi.nlm.nih.gov
  40. 40Intra-Articular Injection of BPC 157 for Multiple Types of Knee Pain Alternative Therapies in Health and Medicine, Jul 2021. pubmed.ncbi.nlm.nih.gov
  41. 41Thymosin beta4 accelerates wound healing Journal of Investigative Dermatology, Sep 1999. pubmed.ncbi.nlm.nih.gov
  42. 42Thymosin beta 4 and a synthetic peptide containing its actin-binding domain promote dermal wound repair in db/db diabetic mice and in aged mice Wound Repair and Regeneration, 2003. pubmed.ncbi.nlm.nih.gov
  43. 43Thymosin beta4 activates integrin-linked kinase and promotes cardiac cell migration, survival and cardiac repair Nature, 25 Nov 2004. pubmed.ncbi.nlm.nih.gov
  44. 44Thymosin β4 enhances the healing of medial collateral ligament injury in rat Regulatory Peptides, 10 Jun 2013. pubmed.ncbi.nlm.nih.gov
  45. 45Muscle injury-induced thymosin β4 acts as a chemoattractant for myoblasts Journal of Biochemistry, Jan 2011. pubmed.ncbi.nlm.nih.gov
  46. 46Bulk Drug Substances Nominated for Use in Compounding Under Section 503A of the Federal Food, Drug, and Cosmetic Act (categories list) U.S. Food and Drug Administration, 14 May 2026. fda.gov
  47. 47Bulk Drug Substances Nominated for Use in Compounding Under Section 503B of the Federal Food, Drug, and Cosmetic Act (categories list) U.S. Food and Drug Administration, 21 Mar 2025. fda.gov
  48. 48World Anti-Doping Code International Standard: Prohibited List 2027 World Anti-Doping Agency, 21 Sep 2026. wada-ama.org
  49. 49Warning letter to Advanced Nutriceuticals, LLC dba The Guyer Institute of Molecular Medicine (MARCS-CMS 615908) U.S. Food and Drug Administration, 10 Nov 2021. fda.gov
  50. 50July 23-24, 2026: Meeting of the Pharmacy Compounding Advisory Committee U.S. Food and Drug Administration, 6 Aug 2026. fda.gov
  51. 51Unauthorized injectable peptide drugs seized from Optimum Wellness Centre in Calgary, Alberta may pose serious health risks (RA-77218) Health Canada, 1 Apr 2025. recalls-rappels.canada.ca
  52. 52Equine Doping Controls of Thymosin β 4: A Population Study and Strategy for Misuse Detection Drug Testing and Analysis, Jul 2025. pubmed.ncbi.nlm.nih.gov
  53. 53Essendon supplements saga: Players banned for 12 months after WADA appeal upheld by Court of Arbitration for Sport ABC News (Australia), 12 Jan 2016. abc.net.au
  54. 54Safety and Efficacy of Thymosin Beta 4 Ophthalmic Solution in Patients With Dry Eye (NCT01387347) ClinicalTrials.gov, 10 Jul 2015. clinicaltrials.gov

Not medical advice. This page reports what studies and regulators say; it does not recommend using any product. How we grade evidence · Report an error.