TB-500 Complete Guide: What the Research Shows in 2026

What is TB 500?

TB 500 is a lab-made peptide, a chain of seven amino acids, the building blocks of proteins. It copies one small piece of thymosin beta-4, a natural repair protein. FDA says the two are not the same substance. No published study has given TB-500 to people, so its effects in humans are unknown.

TB-500 is a heptapeptide. That means a chain of seven amino acids. It copies the LKKTETQ sequence of thymosin beta-4, amino acids 17 to 23. It also has an acetyl group, a small chemical cap, at the front. That is how FDA's 2026 review describes it. The parent protein is 43 amino acids long. It was first taken from calf thymus, a gland in the chest, in 1981 work. Later studies found it in many cell types. It is also in blood, saliva and tears.

FDA says TB-500 appears to have first been synthesized from thymosin beta-4 in 2003. The 2003 study it cites tested the chain without the acetyl cap. A vet product came out in 2011. FDA says it was marketed to boost performance in equine and greyhound sports. The fragment keeps LKKTET, the part of the parent protein that binds actin. Actin is the protein that forms a cell's inner skeleton. Some researchers think the fragment may handle actin the way the whole protein does. FDA says this has been hypothesized, not shown. It adds that the acetyl cap can change how a peptide acts.

A 2026 scoping review in Applied Sciences searched PubMed, Europe PMC and ClinicalTrials.gov through March 2026. A scoping review maps what research exists. It took in 80 studies. Most tested thymosin beta-4, not TB-500. Just one study looked at TB-500 directly. Most of the human data was on the eye and on skin wounds (McGuire et al., Applied Sciences, 2026).

This content is for educational purposes only. These compounds are intended for research use. Nothing here is medical advice. Always work with a qualified clinician before making changes to your health protocol.

What does TB 500 do?

Nobody has shown what TB-500 does in a living body.

FDA found no animal study of whether TB-500 itself helps wounds heal. A 2024 lab study made scratch wounds in fibroblasts, the cells that build connective tissue. TB-500 did not speed their closing. One of its breakdown products, Ac-LKKTE, did. The authors think past healing reports may come from that product, not TB-500 (Rahaman et al., 2024). Most of the work below is on the parent protein, thymosin beta-4 (Tβ4). In lab and animal work, Tβ4 helped cells move. It helped grow new blood vessels, and it damped inflammation.

The core job: holding actin

When tissue is hurt, repair cells must crawl to the site. Those include fibroblasts and endothelial cells. Endothelial cells line blood vessels. Crawling runs on actin. The cell pushes out a front edge. Then it rebuilds its skeleton as it moves.

A 2005 review calls Tβ4 the major actin-sequestering molecule in eukaryotic cells (Goldstein et al., Trends Mol Med, 2005; PMID 16099219). Eukaryotic cells are cells with a nucleus, like ours. Sequestering means held in reserve. So it keeps a store of loose actin units ready for use. A 2004 study mapped how actin passes between it and profilin, another actin protein (Irobi et al. 2004). FDA notes that this store of actin matters for cell shape and movement. No one has tested whether TB-500 does any of this in the body.

New blood vessels at healing sites

Tβ4 drives new vessel growth in animal studies. In developing rodent (mouse) hearts, it was needed for the heart's own vessels to form. The authors call Tβ4 and one of its breakdown products potent drivers of new heart vessels (Smart et al., Nature, 2007). In rodent (rat) skin wounds, treated wounds grew more new vessels (Malinda et al., 1999). No study has tested this for TB-500 in people.

Less inflammation

One study used human eye surface cells grown in a dish. The cells were stimulated with TNF-alpha, a signal that sets off inflammation, with or without Tβ4. Tβ4 blocked NF-kappaB, a switch that turns inflammation on (Sosne et al., Exp Eye Res, 2007). That finding is for Tβ4 in a dish, not TB-500 in the body.

Stem and progenitor cells

Progenitor cells are early cells that grow into tissue. Smart et al. (2007) kept pieces of adult rodent (mouse) heart in a dish. Tβ4 woke resting cells from the heart's outer layer. Those cells then turned into fibroblasts, smooth muscle cells and endothelial cells. A 2021 review sums up what Tβ4 does, from animal experiments and clinical trials (Xing et al., Front Endocrinol, 2021; PMC8724243). It grows new vessels and helps cells multiply. It also cuts cell death and inflammation.

What are the TB 500 benefits?

Nearly all the evidence is preclinical. That means animals and cells. The animal data covers skin wounds, heart repair and nerve damage in diabetes. Human data covers the full Tβ4 molecule, not the TB-500 fragment. For TB-500 itself, FDA found no human data and no animal wound study.

Wound healing

Most of the human work on Tβ4 is here and in the eye, the 2026 review found. Malinda et al. (1999) tested Tβ4 on deep skin wounds in rodent (rat) models (PMID 10469335). By day 4, skin regrowth over the wound was 42% ahead of saline (salt water) controls. By day 7 it was up to 61% ahead. Treated wounds also shrank at least 11% more by day 7. Collagen and new vessels both went up.

The drug firm RegeneRx later took Tβ4 into Phase II trials. Those are larger tests in patients. One enrolled 72 people with leg ulcers from poor vein flow. They put a Tβ4 gel or a dummy gel on the ulcer daily, for up to 84 days (NCT00832091). Another tested a gel on pressure ulcers, or bed sores (NCT00382174). Eye drops made from Tβ4 have finished Phase 3 trials, the large final stage, for dry eye (NCT02974907, NCT03937882). In both trials, of 601 and 700 people, the drops and placebo (a dummy) scored almost the same on the main measures. Drugs@FDA lists no approved Tβ4 product.

Cardiac repair

Bock-Marquette et al. (2004) published a Nature paper. Tβ4 switched on integrin-linked kinase, a signal that helps cells survive, in rodent (mouse) hearts (Nature, 2004). After a heart attack was induced, more heart muscle cells survived early, and heart function improved. Smart et al. (2007) found Tβ4 restarted resting epicardial progenitor cells from adult rodent (mouse) hearts (Smart et al., Nature, 2007). Those are early cells from the heart's outer layer.

In people, a Phase I trial tested safety in 40 healthy volunteers. They got Tβ4 or a placebo (a dummy) into a vein. Adverse events, meaning health problems during a trial, were infrequent and mild or moderate (Ruff et al., 2010). A RegeneRx Phase 1 trial of Tβ4 in a vein was withdrawn and never started (NCT00743769). A Beijing company has finished two Phase 2 heart attack trials of Tβ4. ClinicalTrials.gov shows no results for either (NCT05485818, NCT05984134).

Muscle, tendon and ligament

Here the evidence is thin even in animals. The 2026 scoping review found few studies on tendon, ligament, muscle and cartilage (McGuire et al., 2026). It found little human data for these uses. We found no controlled human trial of TB-500 or Tβ4 for muscle or tendon injury on ClinicalTrials.gov.

Nerve pain and neuropathy: what the animal data shows

Nerve repair needs a steady blood supply and healthy Schwann cells. Schwann cells are the support cells of nerves. They build myelin, the fatty coat around nerve fibres.

One study treated diabetic rodents (mice) with Tβ4 (Wang et al., 2012; PMC3533234). Blood vessels and blood flow in the sciatic nerve, the main nerve of the leg, went up. Nerve function improved. Angiopoietin-1 (Ang1), a signal that keeps vessels stable, rose in the vessel and Schwann cells. Ang2, a related signal that can loosen vessels, fell. The authors think Tβ4 acts on those cells to protect the nerve's blood supply.

Wang et al. (2015) ran longer treatment (Wang et al., J Diabetes Res, 2015; PMID 25945352). Diabetic rodents (mice) got Tβ4 or saline for 16 weeks. Nerve signals got faster. Intraepidermal nerve fiber density rose, meaning more nerve endings in the skin. Diabetes shrinks nerve fibres and their myelin. That loss was held back. Nerve cells from the diabetic rodents (mice) also grew longer branches in a dish. Tβ4 did not change blood sugar. The authors think the Ang1/Tie2 signal path may drive the regrowth. Tie2 is the receptor that Ang1 acts on.

No trial of Tβ4 or TB-500 for peripheral neuropathy appears on ClinicalTrials.gov. Peripheral neuropathy means nerve damage in the limbs. So this stays animal research.

For another thymosin peptide, see my Thymosin Alpha-1 guide.

Is there a proven TB 500 dosage?

No. FDA found no clinical study or human exposure data for TB-500 by any route. So no dose has been tested in people, and there is no FDA-approved dose.

The doses on record come from animal studies of how the body processes TB-500, FDA's review reports. Horses got 10 mg under the skin. Rodents (rats) got 50 mg per kg into the belly. Sellers offer 2, 3, 5, 10 and 15 mg powders labelled for research use only, FDA found. None of these amounts is tied to a safe dose in people.

The parent protein, Tβ4, is a different substance. The Phase I trial gave it into a vein for 14 days. Daily doses ran from 42 to 1,260 mg (Ruff et al., 2010). That tells you nothing about a dose of TB-500.

Is there a TB-500 dosage calculator?

Yes, but only as a unit converter. No study on this page gives a bodyweight dose for people.

The site's TB-500 calculator turns a vial size, the water added and a dose you enter into syringe units. Any dose it shows is only an example, not a studied dose. No study has set a TB-500 dose for people. For the dose question in full, see our TB 500 dosage page.

What are the TB-500 side effects?

No one knows, because no published study has given TB-500 to people. FDA says its safety risks in humans are unknown. FDA found no animal toxicity studies of any kind. It searched FAERS, its main adverse event database, up to 26 March 2025. It found no TB-500 reports there. A second FDA database, for foods and supplements, held two cases about blended TB-500 and BPC-157. FDA says those reports did not include safety assessments.

The parent protein has trial data. In the leg ulcer gel trial, serious adverse events hit 3 of 55 on Tβ4. They hit 1 of 17 on placebo. The posted results mark each one as not related to Tβ4. Other adverse events hit 35 of 55 on Tβ4 and 11 of 17 on placebo. The Phase I vein trial had no serious adverse events. These results are for Tβ4, not an injected TB-500 product. Our TB-500 side effects guide covers the full record.

Known and theoretical concerns

• Immune reactions: FDA says injected TB-500 may pose a significant risk of immunogenicity. That means the immune system reacts to it. Reactions can range from no apparent symptoms to life-threatening.
• Impurities: FDA found no public tests for impurities, clumps or endotoxin in TB-500. Endotoxin is a toxin left by bacteria.
• Wrong substance: FDA found several forms of the peptide sold under the one name.
• Growth-promoting mechanisms: Tβ4 promotes new vessel growth in animals. In rodent (mouse) melanoma models, tumour cells making extra Tβ4 grew tumours with more blood vessels (Cha et al., 2003). FDA found no cancer studies of TB-500.
• No pregnancy data: FDA found no studies of its effects on fertility, pregnancy or unborn young.
• A blend report: FDA's BPC-157 review tells of one report on a BPC-157 and TB-500 blend. The woman's skin and gums darkened. It happened again when she used it again.

Have BPC 157 and TB 500 been tested together?

No study can answer that. FDA found no study that gave TB-500 to people, alone or with BPC-157. FDA's BPC-157 review does cite one knee-pain chart review, Lee and Padgett 2021. It gave BPC-157 "alone or combined with thymosin-beta-4 (TB4)". FDA's summary names it as Tβ4, not TB-500.

The two are sold together all the same. FDA's BPC-157 review lists injections and nasal sprays that hold both. The table sets out what the record shows for each.

For the full mechanism split, see my BPC-157 vs TB-500 comparison. For knees, see the peptide protocol for knee cartilage and osteoarthritis.

Other peptides named beside it

FDA found no controlled study of TB-500 with another peptide.

What's the BPC 157 TB 500 blend dosage?

I can't answer that from the sources on this page. None of them tested a pre-mixed blend, at any strength.

None tested a blend schedule either. FDA's BPC-157 review describes one FAERS report on a blend. It was a 5 mg and 5 mg product labelled for research only. FDA's TB-500 review adds that a supplement complaint search "retrieved two cases about 'blended TB-500 and BPC-157'". So I won't print a per-day blend number here.

What is the TB 500 peptide's legal status in 2026?

TB-500 is not an FDA-approved drug. No pharmacy may make it up under section 503A today. FDA took it off its Category 2 list in April 2026, then proposed not adding it to the bulks list. WADA bans it outright. The two rulebooks are separate.

What changed with the FDA

Section 503A of the drug law covers pharmacies that compound (custom-make) a drug. It lets them use a raw bulk ingredient in only three cases. The first is a USP or NF monograph, an official quality standard. The second is being part of an FDA-approved drug. The third is a place on FDA's 503A bulks list, 21 CFR 216.23. FDA's review found TB-500 meets none of the three.

A pharmacy group, Wells Pharmacy Network, put TB-500 forward for the bulks list. In September 2023, FDA put Thymosin Beta-4, Fragment (LKKTETQ) in Category 2. 18 other substances went in with it. FDA says that group may present significant safety risks. FDA said it added them "because FDA has identified significant safety risks with these substances". On 22 April 2026, FDA removed TB-500 from Category 2 because the nomination was withdrawn. It did not move to Category 1.

Removal isn't permission. FDA still reviewed TB-500 for its advisory meeting of 23 and 24 July 2026. In that review, FDA proposed not adding TB-500 to the bulks list. FDA's Pharmacy Compounding Advisory Committee is a panel of outside experts. It gives FDA advice. The National Community Pharmacists Association reported that it recommended BPC-157, KPV, TB-500, MOTS-c, epitalon and Semax. NCPA reported that the committee rejected adding emideltide. The vote is advisory. FDA's meeting page lists no minutes or vote record.

A substance joins the bulks list only through a formal rule process, with public comment. If FDA agrees, lawful compounding could begin only after a final rule. No proposed rule has been published. See my FDA reclassification explainer and the legal status overview.

WADA is a separate rulebook

WADA's list has nothing to do with FDA compounding rules. The 2026 WADA Prohibited List names "Thymosin-ß4 and its derivatives e.g. TB-500" under S2.3. It is banned at all times, in and out of competition. S2.3 is the growth factor part of S2. S2 covers peptide hormones, growth factors, related substances and mimetics, meaning substances that copy their action. In April 2025, a Canadian university volleyball player got a four-year ban. The athlete had used TB-500 and BPC-157. The case rested on information submitted to the Canadian Centre for Ethics in Sport (CCES).

Research use

A "research use only" label does not make a product lawful to sell for people. In a 2024 warning letter about other research-labelled peptides, FDA said such products were still unapproved new drugs. FDA's safety-risk page still lists TB-500, under substances nominated but withdrawn.

What Does a TB-500 Quality Check Look For?

A certificate of analysis, or CoA, is a lab report on one batch. HPLC means high-performance liquid chromatography, a purity test. On a CoA, mass spectrometry is used to confirm identity. It does not test sterility.

The public CoA FDA reviewed for TB-500 left out key tests. They show no tests for impurities, clumps, germs or endotoxin. FDA also found several forms of the peptide sold under the one name. It adds that how a peptide is made affects its stability and its risk of immune reactions.

See my how to vet a peptide supplier guide and how to read a peptide CoA. My recommended sources page lists vendors that meet UB's standards. The grey market problem and legal peptide access piece covers why the gap exists.