TB-500 Benefits and Side Effects: What Studies Show

Update History ▾

October 27, 2026: Initial publication, built from FDA’s 2026 TB-500 briefing document, FDA’s Category 2 page, the WADA Prohibited List and the fact-checked TB-500 and thymosin beta-4 source set.
Research-use-only framing applied throughout in line with Remy editorial standards.

TL;DR — Research Summary

Most claimed TB-500 benefits (faster wound healing, injury recovery, muscle repair and reduced inflammation) come from studies of full-length thymosin beta-4, the larger natural protein, not from TB-500 itself. FDA found no human data on TB-500 by any route and no study in which it was given to patients.^[1] A 2024 analysis noted that the biological effects of TB-500 had not been documented.^[2]

TB-500 side effects in people are therefore unknown rather than shown to be mild. FDA’s 2026 review found no adverse-event reports in its main database, no nonclinical toxicity studies of any kind and a possible risk of immune reactions, and concluded that its potential safety risks in humans are unknown.^[1] TB-500 is not FDA-approved, is banned in sport, and Remy Research supplies it for in-vitro laboratory research only.

Compliance note: this page is a research review, not a treatment guide. It does not provide human-use dosing, therapeutic recommendations, or any clinical-use instructions, and should be read in the same non-therapeutic frame required across Remy's research content.

What Is TB-500?

TB-500 is a synthetic peptide of seven amino acids, Ac-LKKTETQ: residues 17 to 23 of thymosin beta 4 with an acetyl group added at the start.^[1]^[3] In thymosin beta-4, that short segment is the active region responsible for actin binding, cell migration and wound healing.^[3] Thymosin beta-4 itself is a naturally occurring protein of 43 amino acids that supports the repair and regeneration of injured tissue; after injury it is released by platelets and by immune cells such as macrophages.^[4]

Two points prevent the most common mix-ups. First, TB-500 does not contain Ac-SDKP, the anti-fibrotic fragment that comes from the first four residues of thymosin beta-4, so findings on Ac-SDKP do not apply to it.^[5] Second, products sold under the name vary: anti-doping laboratories found that TB500 products bought online were not consistent with their descriptions.^[6]

How TB-500 Is Thought to Work: Actin Regulation and Cellular Migration

The full protein binds actin, the protein that builds the cell’s internal skeleton, and so promotes cell migration toward injured tissue, including the movement of stem and progenitor cells that form new blood vessels. It also reduces apoptosis, inflammation and the number of myofibroblasts in wounds, which is linked to less scarring and better tissue repair.^[4] Because LKKTETQ is the actin-binding site, TB-500 is assumed to share part of this primary mechanism.^[3]

The direct evidence is mixed. The unacetylated fragment LKKTETQ promoted dermal wound repair in aged mice about as well as the full protein.^[7] But when TB-500 itself was tested in a fibroblast wound-healing assay, the parent peptide had no significant effect; only its metabolite Ac-LKKTE did, and the authors suggest earlier reported activity may come from that metabolite.^[2]

Potential TB-500 Benefits in Research

The table labels each claim by the molecule actually tested. Most rows are thymosin beta-4, not TB-500.

TB-500 — Claimed Benefits and the Evidence Behind Them

Claimed benefit	What was reported	Evidence type
Wound healing	LKKTETQ fragment aided repair in aged mice	Animal (fragment)
Tendon repair	Stronger, better-organised Achilles repair	Animal (rat)
Cell migration	Metabolite Ac-LKKTE active; parent not	Cell culture
Heart repair	Smaller infarcts, better heart function	Animal (full Tβ4)
Dry eye	Mixed results in phase 3 eye-drop trials	Human (full Tβ4)
Reduce inflammation	Fewer inflammatory signals after injury	Cell, animal (full Tβ4)

Accelerated Wound Healing and Tissue Repair

In a rat full-thickness wound model, thymosin beta-4 sped the healing process: re-epithelialisation rose by up to 61% at day 7, with more wound contraction, collagen deposition and new blood vessels, and keratinocyte migration increased.^[8] In later full-thickness skin wounds, thymosin beta-4 increased wound contracture and collagen deposition in diabetic mice and sped healing in aged mice; the seven-amino-acid fragment LKKTETQ matched the parent molecule in the aged animals.^[7] In rat incisional wounds treated locally, the full protein organised collagen into mature connective tissue, reduced myofibroblasts and left minimal scarring, a sign of earlier tissue remodeling.^[9] The fragment result in aged mice is the closest published support for the claim that TB-500 can promote healing, and it used the unacetylated fragment, not TB-500 as sold.

Muscle Injuries, Muscle Repair and Injury Recovery

In a 2026 rat study of Achilles tendon repair, a peptide the authors call TB-500 gave a higher maximum load to failure and better tendon architecture after four weeks than controls; combining it with BPC-157 added no further benefit.^[10] The paper does not state the peptide’s sequence. A 2026 scoping review of six peptides, including TB-500, found that 67% of publications used animal studies, which showed promising but variable effects on tendon, muscle, bone and ligament healing, and that claimed benefits for muscle recovery, musculoskeletal injuries and soft tissue injuries remain unsubstantiated by human trials.^[11] No study has measured faster healing of damaged tissue or soft tissue repair with TB-500 in people.

Heart Repair and Blood Vessel Formation

After experimental heart attacks in mice, the full protein promoted cardiac cell migration, cell survival and cardiac repair.^[12] New blood vessel formation and blood vessel growth are among the actions attributed to the full protein.^[4] None of this cardiovascular work tested TB-500.

Hair Follicle Stem Cells and Nerve Regeneration

A 2004 study reported that thymosin beta-4 increases hair growth by activating hair follicle stem cells.^[13] A 2026 case report described three patients with nerve injury after oral surgery whose sensation recovered after treatment that combined a peptide described as TB-500 with BPC-157, ARA-290, dexamethasone and a local anaesthetic; the authors state that the cases were uncontrolled and that causality cannot be established.^[14] Neither result shows an effect of TB-500 alone.

Can TB-500 Reduce Inflammation?

Anti-inflammatory properties are described for full-length thymosin beta-4, which reduces inflammation and apoptosis after injury and lowers myofibroblast numbers in wounds, a sign of less scarring and better tissue regeneration.^[4] No study has measured an anti-inflammatory effect of TB-500 itself, and none has tested it in chronic inflammation.^[1]

Regenerative Medicine Trials: Full Thymosin Beta-4, Not TB-500

There is no published human study of TB-500, and the full protein has only limited human data from tissue repair trials in the eye and heart.^[1] The human trials below tested full-length thymosin beta-4:

Dry eye, phase 2. In nine patients with severe dry eye, thymosin beta-4 eye drops (RGN-259) improved discomfort and corneal staining compared with vehicle and were well tolerated.^[15]
Dry eye, phase 3. Across the ARISE-1 to ARISE-3 trials in over 1,600 patients, ARISE-3 did not meet its pre-specified co-primary endpoints; some sign and symptom measures improved in subgroups and pooled analyses.^[16]
Neurotrophic keratitis. In the 18-patient SEER-1 trial, 6 of 10 treated patients and 1 of 8 on placebo had complete corneal healing at four weeks (p = 0.0656 on the primary test).^[16]
Heart attack. In a randomised trial of 96 patients, recombinant thymosin beta-4 did not reduce overall infarct size versus placebo; infarcts were smaller only when treatment began within 8 hours.^[17]

None of these products is approved by FDA, and none of the results can be transferred to the TB-500 fragment.

TB-500 Side Effects and Potential Risks

FDA’s 2026 briefing is the most complete safety review of TB-500. Its findings:

Adverse-event reports. FDA’s adverse-event database returned no reports and the literature search found no cases. A separate search found two reports about “blended TB-500 and BPC-157” that contained no safety assessment.^[1]
No toxicity studies. FDA found no acute, repeat-dose, genotoxicity, reproductive or carcinogenicity studies of TB-500.^[1]
Immune system reactions. As an injected peptide, TB-500 may pose a significant immunogenicity risk, which aggregation and peptide-related impurities could amplify.^[1]^[18]
Tumor growth. Thymosin beta-4 and related β-thymosins are studied in cancer biology because they are involved in tumor cell migration and metastasis.^[19] With no carcinogenicity data, whether TB-500 affects tumor growth is unknown.^[1]
Product identity. Products labelled TB500 have been found inconsistent with their stated contents.^[6]
Cell toxicity. In fibroblast tests, neither the synthetic peptide nor its metabolites were cytotoxic.^[2]

FDA’s conclusion: there is a lack of clinical and nonclinical safety information, and the potential safety risks of TB-500 in humans are unknown.^[1] There are no long term safety data and no data on drug interactions.

Is TB-500 FDA Approved?

Where TB-500 stands as of October 27, 2026.

FDA approval. No. TB-500 is not an approved drug, and FDA found no information on its use to treat any disease or condition.^[1]
Compounding. FDA’s Category 2 page lists TB-500 under “nominated but withdrawn.”^[18] FDA’s reviewers proposed not adding it to the compounding list; on July 23, 2026 the advisory committee voted 8–6, with one abstention, to recommend it. The vote is advisory.^[1]^[20]
Sport. WADA lists “thymosin-β4 and its derivatives e.g. TB-500” under S2 (peptide hormones, growth factors and related substances), prohibited at all times.^[21]
UAE. TB-500 is not a registered medicine. Remy Research sells it for in-vitro laboratory research only, not for human use, human consumption or veterinary use.

TB-500 vs BPC-157 and Other Research Peptides

TB-500 is most often compared with BPC-157, a 15-amino-acid gastric peptide with a different mechanism and its own small human record. In the 2026 rat tendon study the combination did no better than either peptide alone.^[10] See BPC-157 vs TB-500 and BPC-157 benefits and side effects. TB-500 is also one of the three components of the GLOW blend, with BPC-157 and GHK-Cu: see GLOW peptide benefits and side effects and GHK-Cu side effects and benefits.

What the Research Does Not Yet Show

Any human data. No study has given TB-500 to people.^[1]
Activity of TB-500 itself. Its own biological effects remain undocumented; one test found only a metabolite active.^[2]
Safety studies. No toxicology or carcinogenicity studies exist.^[1]
A transfer from thymosin beta-4. Trials of the full protein, including its mixed eye-drop results, do not test the fragment.^[16]^[17]

TB-500 for Laboratory Research

Remy Research supplies TB-500 for in-vitro research as the TB-500 10mg research vial, the TB-500 20mg pen and the Genovare TB-500 25mg AQ pen. Each product page carries its batch testing details. For the full mechanism review and the TB-500 versus thymosin beta-4 labelling question, read the TB-500 research review.

Our Research Standards

This article prioritizes primary literature, trial records and regulator documents, and keeps TB-500 data apart from full-length thymosin beta-4 data. Where the human record is absent, we say so directly. No therapeutic, dosing or administration guidance is given. Read our editorial policy →

Editorial Review

Remy Research Editorial Team

Editorial Board, Remy Research

The Remy Research Editorial Board reviews Remy's peptide research library, with a focus on analytical verification, clinical-trial interpretation, and compliance-safe scientific communication.

About the editorial team →

TB-500 Benefits and Side Effects FAQ

What are the benefits of TB-500?

The reported benefits (wound healing, tendon repair, heart repair and reduced inflammation) come mainly from animal studies, most of them of full-length thymosin beta-4. TB-500 has never been tested in people.^[7]^[10]^[1]

What are the side effects of TB-500?

They are unknown. FDA found no adverse-event reports in its main database and no toxicity studies, and warned of a possible risk of immune reactions; it concluded that the safety risks in humans are unknown.^[1]

Is TB-500 safe?

Its safety has not been established. There are no human studies and no nonclinical toxicity or carcinogenicity studies.^[1]

Is TB-500 FDA approved?

No. An FDA advisory committee voted 8–6 in July 2026 to recommend it for the compounding list, against FDA reviewers’ advice; the vote is non-binding.^[20]^[1]

Is TB-500 the same as thymosin beta-4?

No. TB-500 is a seven-amino-acid fragment, Ac-LKKTETQ, of the 43-amino-acid protein, and it does not contain the Ac-SDKP fragment.^[3]^[5]

What is TB-500 good for in research?

It is used as a research compound to study actin binding, cell migration and wound repair, and anti-doping laboratories study it to detect misuse.^[3]^[2]

Is TB-500 banned in sport?

Yes. WADA lists thymosin-β4 and its derivatives, including TB-500, under S2, prohibited at all times.^[21]

TB-500 or BPC-157: which has more evidence?

TB-500 has no human data at all; BPC-157’s small human record is covered in its own article. In one rat tendon study, each helped and the combination added nothing.^[1]^[10]

Sources

U.S. Food and Drug Administration. FDA Briefing Document: TB-500-Related Bulk Drug Substances (TB-500 (free base) and TB-500 acetate). Pharmacy Compounding Advisory Committee Meeting, July 23-24, 2026. fda.gov/media/193349 ↩
Rahaman KA, Muresan AR, Min H, et al. Simultaneous quantification of TB-500 and its metabolites in in-vitro experiments and rats by UHPLC-Q-Exactive orbitrap MS/MS and their screening by wound healing activities in-vitro. J Chromatogr B Analyt Technol Biomed Life Sci. 2024;1235:124033. doi: 10.1016/j.jchromb.2024.124033 · PMID: 38382158 ↩
Ho EN, Kwok WH, Lau MY, et al. 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;1265:57-69. doi: 10.1016/j.chroma.2012.09.043 · PMID: 23084823 ↩
Goldstein AL, Hannappel E, Sosne G, Kleinman HK. Thymosin β4: a multi-functional regenerative peptide. Basic properties and clinical applications. Expert Opin Biol Ther. 2012;12(1):37-51. doi: 10.1517/14712598.2012.634793 · PMID: 22074294 ↩
Cavasin MA. Therapeutic potential of thymosin-β4 and its derivative N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) in cardiac healing after infarction. Am J Cardiovasc Drugs. 2006;6(5):305-311. PMID: 17083265 ↩
Delcourt V, Garcia P, Chabot B, et al. TB500/TB1000 and SGF1000: A scientific approach for a better understanding of misbranded and adulterated drugs. Drug Test Anal. 2023;15(4):458-464. doi: 10.1002/dta.3421 · PMID: 36482504 ↩
Philp D, Badamchian M, Scheremeta B, et al. Thymosin 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 Regen. 2003;11(1):19-24. doi: 10.1046/j.1524-475x.2003.11105.x · PMID: 12581423 ↩
Malinda KM, Sidhu GS, Mani H, et al. Thymosin beta4 accelerates wound healing. J Invest Dermatol. 1999;113(3):364-368. doi: 10.1046/j.1523-1747.1999.00708.x · PMID: 10469335 ↩
Ehrlich HP, Hazard SW. Thymosin beta4 enhances repair by organizing connective tissue and preventing the appearance of myofibroblasts. Ann N Y Acad Sci. 2010;1194:118-124. doi: 10.1111/j.1749-6632.2010.05483.x · PMID: 20536458 ↩
Biçer O, Adanir O, Güleryüz Y, et al. Effects of BPC-157 and TB-500 on Achilles tendon healing in rats: A histopathological and biomechanical study. Jt Dis Relat Surg. 2026;37(3):822-837. doi: 10.52312/jdrs.2026.2951 · PMID: 42542926 The paper describes its TB-500 as synthetic thymosin beta-4 and does not state its sequence. ↩
Tewari K, Liu TP, Im C, et al. Peptide Supplements and Their Therapeutic Applications in Sports Medicine. Am J Sports Med. 2026 (online August 11, 2026). doi: 10.1177/03635465261464420 · PMID: 42578445 ↩
Bock-Marquette I, Saxena A, White MD, Dimaio JM, Srivastava D. Thymosin β4 activates integrin-linked kinase and promotes cardiac cell migration, survival and cardiac repair. Nature. 2004;432(7016):466-472. doi: 10.1038/nature03000 · PMID: 15565145 ↩
Philp D, Nguyen M, Scheremeta B, et al. Thymosin beta4 increases hair growth by activation of hair follicle stem cells. FASEB J. 2004;18(2):385-387. doi: 10.1096/fj.03-0244fje · PMID: 14657002 ↩
Froum S, Estrin N, Pico G, et al. Case Report: Regenerative peptides for Inferior alveolar nerve injury: a narrative review with hypothesis-generating three clinical cases. Front Oral Health. 2026;7:1907109. doi: 10.3389/froh.2026.1907109 · PMID: 42876687 ↩
Sosne G, Dunn SP, Kim C. Thymosin β4 significantly improves signs and symptoms of severe dry eye in a phase 2 randomized trial. Cornea. 2015;34(5):491-496. doi: 10.1097/ICO.0000000000000379 · PMID: 25826322 ↩
RegeneRx Biopharmaceuticals. RGN-259 programme page: ARISE-1, ARISE-2 and ARISE-3 dry-eye trials and SEER-1 to SEER-3 neurotrophic keratitis trials. Checked October 27, 2026. regenerx.com/RGN-259 ↩
Zhang Y, Dong Q, Bian X, et al. Recombinant human thymosin beta 4 improves ischemic cardiac dysfunction in mice and patients with acute ST-segment elevation myocardial infarction after reperfusion. Cardiovasc Res. 2025;121(17):2747-2758. doi: 10.1093/cvr/cvaf223 · PMID: 41229390 ↩
U.S. Food and Drug Administration. Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks (Category 2; “Thymosin beta-4, fragment (LKKTETQ), also known as TB-500” under “Bulk drug substances nominated but withdrawn”). Updated April 22, 2026; checked October 27, 2026. fda.gov ↩
Sribenja S, Wongkham S, Wongkham C, Yao Q, Chen C. Roles and mechanisms of β-thymosins in cell migration and cancer metastasis: an update. Cancer Invest. 2013;31(2):103-110. doi: 10.3109/07357907.2012.756111 · PMID: 23320791 ↩
Steinzor P. FDA Panel Backs 6 Peptides for Compounding. AJMC, July 31, 2026. ajmc.com ↩
World Anti-Doping Agency. The Prohibited List (S2: “Thymosin-β4 and its derivatives e.g. TB-500”; prohibited at all times). Checked October 27, 2026; the 2027 List was published September 21, 2026 and takes effect January 1, 2027. wada-ama.org ↩

For catalog details, see the TB-500 10mg research vial, the TB-500 20mg pen and the Genovare TB-500 25mg AQ pen. For editorial standards, continue to the editorial policy.