Thymosin Beta-4 Fragment (TB-500)

Table of Contents

1. What Thymosin Beta-4 Fragment Is
2. Where It Came From
3. How It Is Thought to Work: Laboratory and Animal Research
4. Research on the Full-Length Parent Protein
5. Human Studies of the Fragment
6. What the U.S. Food and Drug Administration Found
7. The July 2026 Advisory Committee Vote
8. The October 2026 Interim Compounding Policy
9. Safety Findings and Unknowns
10. What Is Not Known
11. Key Research Papers
12. Connections
13. Featured Videos

What Thymosin Beta-4 Fragment Is

The U.S. Food and Drug Administration's briefing document for its July 2026 advisory committee describes the substance as “a seven amino acid synthetic fragment of thymosin beta-4 (β4) from amino acids 17 to 23 and an acetyl group at the N-terminal leucine amino acid (Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln-OH).” In one-letter code the chain reads LKKTETQ: leucine, two lysines, threonine, glutamic acid, threonine again and glutamine. The “Ac-” at the front is the acetyl cap.

Fragment, not the whole protein

Thymosin beta-4 itself is a 43-amino-acid protein first isolated from calf thymus. Its own starting end carries an acetyl group, as the 1981 paper that worked out its full sequence reported. The seven-amino-acid stretch at positions 17 to 23 sits in the middle of that chain, so in the natural protein it carries no acetyl cap. A racing laboratory in Hong Kong that studied the veterinary product described its key ingredient as LKKTETQ “with artificial acetylation of the N-terminus.” The U.S. Food and Drug Administration states plainly that “thymosin beta-4 and TB-500 are not the same substance,” even though “several websites state that TB-500 is a synthetic version of thymosin beta-4 and often use the terms interchangeably.” On this page, research on the full 43-amino-acid protein is always labelled as research on the parent protein.

The name

“TB-500” is a trade-style name, not an official one. The briefing notes that it “is a common name and not a United States Adopted Name (USAN),” and that the agency “has encountered multiple salts, and derivatives, including different active moieties, sold commercially under the same common name.” The agency's compounding-safety page lists it as “Thymosin beta-4, fragment (LKKTETQ),” “also known as TB-500.” The 2026 policy of the U.S. Department of Health and Human Services uses only the name “TB-500” and defines the substance by its sequence.

Free base and acetate

Synthetic peptides are made either as the peptide alone (the “free base”) or paired with an acid as a salt. The acetate form is the peptide paired with acetic acid, the acid in vinegar. The two forms weigh differently and are tested differently, so the U.S. Food and Drug Administration treats each one as a separate bulk drug substance, the raw active ingredient from which a pharmacy prepares a medicine. The briefing gives these identifiers:

• Free base: molecular formula C₃₈H₆₈N₁₀O₁₄, molecular weight 889.01; Chemical Abstracts Service registry number 885340-08-9; Unique Ingredient Identifier QHK6Z47GTG.
• Acetate: C₃₈H₆₈N₁₀O₁₄·CH₃COOH, molecular weight 949.1; no registry number or Unique Ingredient Identifier of its own. The briefing notes that “on several suppliers’ websites” the free-base registry number is used for the acetate.

There is no United States Pharmacopeia or National Formulary monograph (an official quality standard) for either form, and neither is part of any drug the U.S. Food and Drug Administration has approved.

Where It Came From

The parent protein came first. In 1981 Low, Hu and Goldstein reported the complete amino acid sequence of bovine thymosin beta-4, a 43-amino-acid peptide from calf thymus that was then studied as a thymic hormone. In 1991 a University of Pennsylvania group (Safer, Elzinga and Nachmias) showed that an actin-binding peptide they had found in human blood platelets was identical to thymosin beta-4. Actin is the protein that forms the internal scaffolding of cells, and later research on the protein turned to cell movement and tissue repair.

Through the late 1990s and 2000s, researchers at the U.S. National Institutes of Health tested thymosin beta-4 on wounds in rats and mice. In 2003 Philp and colleagues reported that a seven-amino-acid synthetic peptide, LKKTETQ, copying the parent protein's actin-binding stretch, promoted wound repair in aged mice about as well as the full protein. The U.S. Food and Drug Administration's briefing dates the fragment's first synthesis to that 2003 study, while noting elsewhere that the 2003 peptide was the non-acetylated fragment, not the acetyl-capped product now sold under the name.

The acetyl-capped product appeared in animal sport. The briefing states that “a veterinary preparation of TB-500 appeared in 2011 and was marketed to boost performance in equine and greyhound sports.” Doping-control laboratories in Belgium and Hong Kong published methods to identify it in 2012: the Belgian laboratory found the acetyl-capped fragment in a product sold as “TB-500” and made it by chemical synthesis as a reference standard, and the Hong Kong racing laboratory detected it and its breakdown products in horses given a single dose.

How It Is Thought to Work: Laboratory and Animal Research

Proposed mechanisms

Every proposed mechanism comes from cell-culture and animal studies, and almost all of it comes from studies of the full parent protein or of the non-acetylated seven-amino-acid stretch, not of the acetyl-capped product.

• Actin binding (parent protein). Thymosin beta-4 binds single actin molecules one-to-one and stops them from joining into filaments. The 1991 study found it holds much of the unassembled actin in resting human platelets. Because cells crawl by building and dismantling actin filaments, this is the starting point for the idea that the protein affects cell movement.
• Active sites (parent protein). A 2010 review by Sosne and colleagues described several short active sites inside thymosin beta-4: a four-amino-acid piece at the start that generally blocks inflammation and reduces scarring, and the central stretch containing LKKTETQ (positions 17 to 23), which the authors linked to new blood-vessel growth, wound healing and cell migration.
• The capped fragment may act through a breakdown product. A 2024 study from a Korean doping-control centre found that the acetyl-capped fragment is broken down into shorter pieces in human serum, in enzyme tests and in rats. In fibroblast (skin connective-tissue) cells, only one breakdown piece, Ac-LKKTE, gave a significant wound-closing effect; the intact fragment did not. The authors suggested that wound-healing effects reported for the product “may be due to its metabolite Ac-LKKTE rather than the parent form.” The 2026 policy of the U.S. Department of Health and Human Services likewise states that “the fragment is rapidly truncated in human serum.”

The U.S. Food and Drug Administration draws the same distinction: “the pharmacological profile of the non-acetylated heptapeptide LKKTETQ cannot be directly extrapolated to the N-acetylated heptapeptide TB-500.” The repair process these studies try to influence is shown in an animation of how wounds heal.

Skin wounds

The 2003 mouse study is the one most often cited for the fragment. In 26-month-old (aged) mice, whose wounds healed slowly, the non-acetylated seven-amino-acid peptide LKKTETQ promoted repair of full-thickness skin wounds “comparable to that observed with the parent molecule.” The same study tested the full protein in diabetic mice. The U.S. Food and Drug Administration notes that this study tested the uncapped fragment, not the acetyl-capped product sold under the name. In the 2024 fibroblast experiments, the acetyl-capped fragment itself, at 50 micrograms per millilitre, closed scratch wounds no differently from the control solution.

Tendons

A 2026 study from Turkey cut and repaired the Achilles tendon in 32 rats and gave four groups daily injections into the abdomen for four weeks: no peptide, Body Protection Compound-157 (BPC-157), a substance the authors call “synthetic thymosin beta-4 (TB-500)” at 60 micrograms per kilogram a day, or both. The group given the thymosin beta-4 product had a significantly higher load-to-failure and better tissue scores than controls; the combination added nothing over either peptide alone. The abstract does not give the product's sequence or source, so it does not establish whether the capped fragment or another form was tested. The authors call the study exploratory. Background on the human condition is on the Achilles Tendinopathy page.

Horses and rats: how long it lasts

In the Hong Kong horse study, the acetyl-capped fragment and its breakdown products were found in blood and urine after a single dose of a veterinary product containing 10 mg of it. The U.S. Food and Drug Administration's summary of that work reports that blood levels peaked at 0.05 and 0.08 nanograms per millilitre between 60 and 120 minutes after the dose and could no longer be measured after 6 to 10 hours. In rats, the 2024 Korean study found a two-amino-acid piece (Ac-LK) as the main breakdown product in the first six hours, and a three-amino-acid piece (Ac-LKK) still detectable up to 72 hours.

What is missing

The U.S. Food and Drug Administration “did not identify” any genotoxicity (damage to genes), developmental and reproductive, or cancer studies of the fragment, and concluded that “nonclinical toxicological studies are not available to inform safety considerations” for either form.

Research on the Full-Length Parent Protein

Everything in this section concerns full-length thymosin beta-4, the 43-amino-acid protein, not the seven-amino-acid fragment. It is reported because the fragment is often promoted on the strength of it, and the U.S. Food and Drug Administration noted that the three references in the fragment's nomination “are studies on Thymosin β4.” A 2026 orthopaedic review describes the fragment as “a distinct seven amino-acid fragment” that is “frequently conflated with full-length TB-4 despite the absence of validated biologic or clinical equivalence.”

Animal studies of the parent protein

• Rat wounds (1999). Given on the skin or into the abdomen, the full protein increased the regrowth of skin over full-thickness wounds by 42% over salt-water controls at 4 days and by as much as 61% at 7 days, with more collagen and new blood vessels.
• Diabetic and aged mice (2003). The full protein sped repair in both kinds of slow-healing mice.
• Cancer cells in mice (2003). A National Institutes of Health study made mouse melanoma (skin-cancer) cells produce extra thymosin beta-4. Tumours from these cells grew larger (mean 21.7 mm against 13.3 mm), and after injection into a vein they formed far more lung tumour nodules (mean 46.7 against 10.9). The authors concluded that the protein “may stimulate tumor metastasis by activating cell migration and angiogenesis.” The experiment raised the protein's level inside cancer cells; it did not inject the protein or the fragment. Background on the disease is on the Skin Cancer page.

Human trials of the parent protein

Unlike the fragment, the full protein has been given to people in early-stage trials:

• Healthy volunteers, into a vein (2010). Four groups of 10 healthy adults received placebo or synthetic thymosin beta-4 at 42, 140, 420 or 1,260 mg as a single dose and then daily for 14 days. Adverse events were infrequent and mild or moderate, with no serious adverse events or dose-limiting toxicity. The trial was aimed at a future use in heart attacks (see Heart Attack).
• Healthy volunteers in China (2021). A lab-made (recombinant) human thymosin beta-4 was given into a vein to 54 people in a single-dose phase and 30 in a 10-day phase. Adverse events were mild to moderate, with no serious ones. Three of the authors were employees of the sponsor.
• Venous leg ulcers (2010). A double-blind, placebo-controlled, dose-escalation trial at eight European sites randomized 73 patients to thymosin beta-4 or placebo applied to the ulcer. Safety was “comparable to placebo.” The authors wrote that a 0.03% dose “may have the potential to accelerate wound healing” and that complete healing within 3 months occurred in about 25% of patients. Related background: Varicose Veins.
• Severe dry eye (2015). A small two-site trial gave 9 patients either 0.1% thymosin beta-4 eye drops or a control solution six times a day for 28 days. At day 56 the treated eyes had 35.1% less discomfort and 59.1% less corneal staining than the control eyes; the authors describe it as a small trial. Background: Dry Eye Disease.

None of these trials tested the fragment, and none used injection under the skin or into muscle, the routes covered for the fragment by the 2026 policy.

Human Studies of the Fragment

The U.S. Food and Drug Administration's May 2026 review found none. It states that “no articles were found in which TB-500 was administered to humans,” that the agency “did not identify clinical studies in humans assessing pharmacokinetics or pharmacodynamics” (how the body absorbs and clears it, and what it does) by any route, and that it found no information in the medical literature where the substance “was administered to patients to treat any disease or condition including its use in wound healing.”

One report published after that review describes human use. A 2026 dental case report described three patients with injury to the inferior alveolar nerve (the nerve to the lower lip and chin) who received weekly injections into the gum for four weeks of a mixture containing three peptides, among them a substance the authors list as “TB-500” and Body Protection Compound-157, together with a steroid (dexamethasone) and a local anaesthetic. All three reported improvement. The authors state that, because every patient got the same mixture and there was no control group, “spontaneous recovery and other confounding factors cannot be excluded, and causality cannot be established.” No controlled trial of the fragment in people was found.

What the U.S. Food and Drug Administration Found

A compounding pharmacy network nominated the fragment for the list of bulk drug substances that pharmacies may compound with, proposing a 3 mg/mL powder for injection under the skin or into muscle for “wound healing.” The nomination was later withdrawn. The U.S. Food and Drug Administration evaluated both forms anyway, “on its own initiative because it is unclear which substance the nominator intended to nominate,” in a briefing memo dated 15 May 2026. It weighs four criteria together, as set by a 2019 rule. The wider review of all seven peptides is on the U.S. Food and Drug Administration compounded peptides review page.

1. Physical and chemical characterization

Neither form was found “physically and chemically well characterized,” because of “inconsistent naming conventions” and because critical data such as possible peptide impurities were missing. No certificate of analysis (a supplier's test report on a batch) was submitted for the free base; one found in the public domain did not control bacterial endotoxin (fever-causing bacterial debris), impurities or aggregates (clumps). The nominator's certificate for the acetate gave no information on identity, strength, aggregates or bacterial endotoxin. The agency was “concerned about the potential for immunogenicity” with injection. Immunogenicity is the ability of a substance to provoke an immune response, for example antibodies against the peptide; clumped peptide and closely related manufacturing impurities can make that more likely.

2. Safety

The agency found “a lack of clinical and nonclinical safety information,” was “particularly concerned about the absence of human data,” and concluded that “potential safety risks associated with the use of these substances in humans are unknown.” Its adverse event searches are described under Safety Findings and Unknowns.

3. Effectiveness for wound healing

“There is a lack of evidence to evaluate the effectiveness” of either form for wound healing. None of the three references in the nomination studied the fragment in people, and the nominator did not say what type of wound it was meant for. The briefing notes that “wounds can be serious or life-threatening” and that approved drugs exist for the same condition. Wound care in general is covered on the Wound Healing page.

4. Historical use, and status in other countries

The agency found no study of the fragment as a compounded drug and no outsourcing facility reporting compounding with it. It is “not recognized in either the European or Japanese Pharmacopeias,” and the briefing found “no approved products containing TB-500 in Canada, Australia, the United Kingdom, Belgium, Ireland, France, Norway, Germany, Spain, and Italy,” and no European Union authorization. It also records that the substance “is on the list of prohibited substances under section S2.3” of the World Anti-Doping Agency.

The agency's proposal

“Accordingly, we propose not adding TB-500 (free base) or TB-500 acetate to the 503A Bulks List.” The briefing bases this on “the lack of data related to physiochemical characterization, lack of historical use in compounding, and the non-existing information on the use of these substances administered in humans.”

Before this review, the agency's compounding-safety page had placed the fragment in “Category 2,” substances that may present significant safety risks in compounding, with a note on possible immunogenicity and no human exposure data. The page as updated in April 2026 lists it instead in a table of substances “nominated but withdrawn,” with the safety note kept.

The July 2026 Advisory Committee Vote

The Pharmacy Compounding Advisory Committee, a panel of outside experts, met on 23–24 July 2026 to consider seven peptides. The fragment was taken on 23 July for wound healing. The committee voted separately on whether each form belonged on the 503A bulks list. The counts were read aloud “for the record” by the agency's meeting officer on the agency's own broadcast of the meeting (addresses in the U.S. Food and Drug Administration webcast information document):

• Thymosin beta-4 fragment, free base: 8 yes, 6 no, 1 abstention.
• Thymosin beta-4 fragment, acetate: 8 yes, 6 no, 1 abstention.

Fifteen members were eligible to vote on this topic according to the agency's final meeting roster, which matches the total. As of 14 November 2026 the agency had posted no written minutes or transcript of the meeting, so the broadcast is the record. The committee recommended six of the seven peptides; it voted against only emideltide.

Advice, not a decision

The committee's votes ran against the agency staff's written proposal, which was not to list either form. The agency's meeting page explains that advisory committees “make non-binding recommendations to the FDA, which generally follows the recommendations but is not legally bound to do so.” An agency participant told the committee on 23 July that the staff recommendations “weren't final decisions. So the final decisions would come out through rulemaking.” As of 14 November 2026 the Federal Register held no proposed or final rule adding the fragment to the list or excluding it.

The October 2026 Interim Compounding Policy

The U.S. Department of Health and Human Services announced its policy, headed “HHS Enforcement Discretion Policy Regarding 503A Compounding Using Certain Peptide Bulk Drug Substances,” in a Federal Register notice of availability published on 30 October 2026 (91 FR 68526–68527), signed by Secretary Robert F. Kennedy, Jr. The notice calls it a “draft” policy; the policy document calls itself an “interim policy.” The full policy is described on the peptide compounding enforcement-discretion policy page.

The terms in plain words

• 503A is the section of the Federal Food, Drug, and Cosmetic Act that lets state-licensed pharmacies, federal facilities and licensed physicians prepare (compound) a medicine for an individual patient's prescription without it going through drug approval.
• The 503A bulks list is the list, made by formal rulemaking, of raw ingredients that may be compounded when no official monograph or approved drug covers them.
• Enforcement discretion means the government states that it does not intend to take action against a practice that the law does not formally permit. It is not a permission or an approval.

What it covers for this peptide

The policy names the fragment only as “TB-500” and covers only the acetate form, identified as Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln-OH·CH₃COOH, formula C₃₈H₆₈N₁₀O₁₄·CH₃COOH, 949.1 g/mol. The free base is not covered. The covered routes are “subcutaneous or intramuscular injectable dosage forms” (under the skin or into muscle), made from an ingredient that comes with a certificate of analysis meeting the policy's conditions. Oral, topical and nasal forms of the fragment are not covered.

The ten conditions, grouped

1. The peptide is on the policy's list of six and matches the identity and routes it sets out.
2. The ingredient comes from a registered manufacturer that follows current good manufacturing practice, with a valid certificate of analysis covering identity, purity, strength and contaminants such as endotoxins, heavy metals and microbes.
3. The compounder reports serious adverse events (whether or not they seem drug-related) and quality problems to the agency's MedWatch program and to the states involved.
4. The label reads “This is a compounded drug product. Not for resale.” The product holds one active ingredient, and the only device packaged with it is a syringe cleared by the agency.
5. Every other requirement of the Act still applies, including a patient-specific prescription and clean (non-insanitary) preparation.

What the policy says about this peptide

The policy's Appendix B states that the agency's Center for Drug Evaluation and Research “recommended against listing either form,” that the committee “voted in favor of both forms,” and that the fragment was in Category 2 “from September 29, 2023, until April 22, 2026,” adding that neither the placement nor the removal changed its status under section 503A. It justifies inclusion on three grounds: that historical use “is now documented and quantified”; that the “characterization record has materially changed” through batch-specific certificates from registered facilities; and that the Center's safety concerns are “inferential rather than observed.” The policy does not name the data behind the first ground.

What it does not do

• It is not an approval. The policy states that “compounded drugs are not FDA-approved, which means FDA does not review their safety, effectiveness, or quality before they are marketed.”
• It does not put the fragment on the 503A bulks list; the notice states that future rulemaking “may propose adding some or all of these peptides.”
• It is not binding: the notice states it “does not establish any rights for any person and is not binding on HHS or the public.”
• It lasts only until a final rule decides whether the peptide is on the list, and the department “may revisit” it early “if, among other things, a safety signal or product quality issue arises.”
• It names only state-licensed pharmacies, federal facilities and licensed physicians. It does not mention outsourcing facilities (section 503B), and it does not mention patient consent.

Status on 14 November 2026

No effective date is stated in the notice or the policy. Comments were accepted in public docket HHS-OASH-2026-0496 until 13 November 2026 at 11:59 p.m. Eastern Time; the Federal Register's record showed about 289 comments received and regulations.gov showed 115 posted. No final version had been found. The agency's compounding-safety page, last updated in April 2026, still listed the fragment among substances “nominated but withdrawn,” and no statement about the policy was found on the agency's website. The Associated Press reported on 28 October 2026, citing six people familiar with its development, that the agency's scientific staff had little input into the policy and opposed the changes; no primary document on that point was found.

Safety Findings and Unknowns

• No human safety data on the fragment. The U.S. Food and Drug Administration found no clinical study of the fragment by any route, and no toxicology studies on genes, reproduction or cancer.
• Adverse event reports. A search of the U.S. Food and Drug Administration Adverse Event Reporting System through 26 March 2025 “did not retrieve any reports” for the fragment, and the literature search found no adverse-event cases. The agency's slides add that “the lack of reports for TB-500 does not imply that the substance is safe or lacks toxicities.” That search ran more than a year before the May 2026 memo. Separately, a report counted under Body Protection Compound-157 described a person who injected that peptide together with “TB500” twice daily and developed widespread darkening of the skin and gums that recurred when the products were taken again.
• Food and supplement complaints. The agency's complaint system for foods and supplements (searched from 2004 to March 2025) held two cases about “blended TB-500 and BPC-157,” neither with a safety assessment.
• Immunogenicity. The agency states that, given by injection, the fragment “may pose a significant risk for immunogenicity, potentially amplified by aggregation as well as potential peptide-related impurities,” and that no study has measured either.
• What is actually in products. The briefing records products labelled “for research use only” on websites, several salts and derivatives sold under the one name, and mislabelled registry numbers. The 2012 Belgian analysis identified the acetyl-capped fragment in a product sold under the name; it did not survey products for purity. A 2026 orthopaedic review states that commercial products “raise concerns regarding identity, purity, concentration, sterility, and manufacturing consistency.” The policy of the U.S. Department of Health and Human Services gives as its reason the “continued, widespread use of certain research-use-only peptides supplied by foreign manufacturers that pose a safety risk to US patients.”
• The cancer question (parent protein). The 2003 mouse study linked higher thymosin beta-4 levels inside melanoma cells with larger tumours and more spread. No study was found that tested whether the fragment itself affects tumours.
• Sport. The substance is on the World Anti-Doping Agency's prohibited list (section S2.3), and laboratories have published methods to detect it and its breakdown products in horses.

What Is Not Known

• Whether the acetyl-capped fragment does anything useful in people. No controlled human trial was found, and the only human report found is three uncontrolled dental cases using a mixture.
• Whether the fragment works at all as itself, or only through a breakdown product; the 2024 cell study found wound-closing activity only in one breakdown piece.
• How much of the parent protein's research applies. The animal and early human results for full-length thymosin beta-4 cannot be transferred to a seven-amino-acid fragment without testing, as the U.S. Food and Drug Administration and a 2026 review both state.
• How it is absorbed, how long it lasts and how it is cleared in humans; the only measurements are in horses and rats.
• Whether injected doses cause antibodies or other immune reactions, and what impurities typical products contain.
• Long-term effects, including any effect on cancer growth, for which no fragment study exists.
• Whether the U.S. Food and Drug Administration will propose adding the fragment to, or excluding it from, the 503A bulks list, and when; and what final form the interim policy will take.

Decisions about medicines, including compounded ones, belong with a clinician who knows the person's history.

Key Research Papers

1. Low TL, Hu SK, Goldstein AL. Complete amino acid sequence of bovine thymosin beta 4: a thymic hormone that induces terminal deoxynucleotidyl transferase activity in thymocyte populations. Proc Natl Acad Sci U S A. 1981;78(2):1162-6. PubMed PMID: 6940133
2. Safer D, Elzinga M, Nachmias VT. Thymosin beta 4 and Fx, an actin-sequestering peptide, are indistinguishable. J Biol Chem. 1991;266(7):4029-32. PubMed PMID: 1999398
3. Malinda KM, Sidhu GS, Mani H, Banaudha K, Maheshwari RK, Goldstein AL, et al. Thymosin beta4 accelerates wound healing. J Invest Dermatol. 1999;113(3):364-8. PubMed PMID: 10469335
4. Philp D, Badamchian M, Scheremeta B, Nguyen M, Goldstein AL, Kleinman HK. 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. PubMed PMID: 12581423
5. Cha HJ, Jeong MJ, Kleinman HK. Role of thymosin beta4 in tumor metastasis and angiogenesis. J Natl Cancer Inst. 2003;95(22):1674-80. PubMed PMID: 14625258
6. Sosne G, Qiu P, Goldstein AL, Wheater M. Biological activities of thymosin beta4 defined by active sites in short peptide sequences. FASEB J. 2010;24(7):2144-51. PubMed PMID: 20179146
7. Esposito S, Deventer K, Goeman J, Van der Eycken J, Van Eenoo P. 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;4(9):733-8. PubMed PMID: 22962027
8. Ho EN, Kwok WH, Lau MY, Wong AS, Wan TS, Lam KK, 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. PubMed PMID: 23084823
9. Rahaman KA, Muresan AR, Min H, Son J, Han HS, Kang MJ, 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. PubMed PMID: 38382158
10. Biçer O, Adanir O, Güleryüz Y, Balci EC, Dinçel YM, Yenigün MY, 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. PubMed PMID: 42542926
11. Ruff D, Crockford D, Girardi G, Zhang Y. A randomized, placebo-controlled, single and multiple dose study of intravenous thymosin beta4 in healthy volunteers. Ann N Y Acad Sci. 2010;1194:223-9. PubMed PMID: 20536472
12. Wang X, Liu L, Qi L, Lei C, Li P, Wang Y, et al. 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;25(17):8222-8228. PubMed PMID: 34346165
13. Guarnera G, DeRosa A, Camerini R; 8 European sites. The effect of thymosin treatment of venous ulcers. Ann N Y Acad Sci. 2010;1194:207-12. PubMed PMID: 20536470
14. 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):491-6. PubMed PMID: 25826322
15. Froum S, Estrin N, Pico G, Yakubov M, Ahmad P, LaValle J. Case Report: Regenerative peptides for Inferior alveolar nerve injury: a narrative review with hypothesis-generating three clinical cases. Front Oral Health. 2026;7:1907109. PubMed PMID: 42876687
16. Tham A, Hodgkins CW, Kennedy JG. Investigational Peptides in Orthopaedic Practice: Evidence, Safety, and Patient Counseling for BPC-157, Thymosin Beta-4, and TB-500. J Am Acad Orthop Surg. 2026 (online ahead of print). PubMed PMID: 42937313

PubMed Topic Searches

1. PubMed: TB-500 and the LKKTETQ fragment
2. PubMed: thymosin beta-4 and wound healing
3. PubMed: thymosin beta-4 clinical trials
4. PubMed: TB-500 doping control

Back to Table of Contents

Connections

• Peptides — the six peptides in the 2026 compounding policy
• Peptide Compounding News — the 14 November 2026 news report
• Peptide Compounding Enforcement Discretion — the interim policy in full
• U.S. Food and Drug Administration Review of Compounded Peptides — the seven-peptide review and committee meeting
• Drugs — every drug page on the site
• Wound Healing — the use the fragment was nominated for
• How Wounds Heal — animation of the repair process
• Achilles Tendinopathy — the tendon studied in the 2026 rat experiment
• Dry Eye Disease — where the parent protein was tested as eye drops
• Lysine — one of the seven amino acids in the fragment

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