TB-500 (Thymosin Beta-4 Fragment): What Lakeland Readers Should Know

TB-500 is often sold as “thymosin beta-4” and paired with BPC-157 for injury recovery. The two names do not describe the same molecule, and that difference shapes everything about the evidence. This page explains what TB-500 is, what research exists and where its status stood in November 2026. It is general information, not advice for your situation.

What it is and how it works

Thymosin beta-4 is a natural peptide made of 43 amino acids. It is found in most cells and in blood, saliva, tears and wound fluid. Its best-known job is binding actin, a protein that forms part of each cell’s inner scaffolding. Lab and animal studies have linked it to cell movement, new blood vessel growth and wound repair.¹

TB-500 is a lab-made fragment of just 7 of those amino acids, with an extra chemical group (an acetyl group) attached. FDA states that “thymosin beta-4 and TB-500 are not the same substance,” even though many websites use the names as if they were.¹ The fragment first appeared in research in 2003. A veterinary TB-500 product appeared around 2011 and was marketed to boost performance in horse and greyhound racing.¹

That added chemical group changes how a peptide behaves. In one lab study, TB-500 itself did not speed the closing of scratch wounds in skin cells, while one of its breakdown products did. FDA also found no animal study testing whether TB-500 helps wounds heal. So results for the full natural protein cannot simply be applied to TB-500.¹

What the research shows (and where evidence is weak)

TB-500 in people: no studies. FDA’s May 2026 review found no clinical studies, no data on how the body handles TB-500, and no published case reports of its use in humans. It also found no animal toxicity studies.¹

Full-length thymosin beta-4: small trials with weak results. Thymosin beta-4 itself has been tested in small trials, mostly run by the companies developing it. A “phase 2” or “phase 3” trial is a mid- or late-stage test of whether a drug works; its “primary endpoint” is the main result it was designed to measure.

• Dry eye drops. A 72-person phase 2 trial missed both of its main goals, though some secondary measures improved.² A later phase 3 trial “did not meet its primary outcome measures,” the sponsor reported in 2021.³
• A hard-to-heal eye-surface condition (neurotrophic keratopathy). In 18 people, 6 of 10 on the drops healed fully at 4 weeks, compared with 1 of 8 on placebo (a dummy treatment). That difference was not statistically significant, meaning it could have been chance. Company employees helped design the trial.⁴
• Gel for leg ulcers. In a 73-patient phase 2 trial, safety was similar to placebo. The authors said the results only “suggest” a possible benefit.⁵
• Heart attack. In a 96-patient trial in China, a lab-made version did not reduce heart damage overall. A benefit was reported only in a subgroup treated early.⁶
• IV use in healthy volunteers. Short early-stage safety studies found it well tolerated.⁷

None of these trials tested TB-500. Even for the full protein, the main results were missed or borderline, and positive claims rest on secondary measures and subgroups.

What marketing claims. Online sellers list tissue repair, tendon and ligament healing, muscle growth, endurance, hair growth and heart health. No human study of TB-500 supports any of these.¹

FDA and regulatory status

Not approved. TB-500 is not FDA-approved and is not part of any approved drug. FDA found no approved TB-500 product in the European Union, the United Kingdom, Canada, Australia or several other countries it checked.¹

FDA’s safety-concern list. FDA lists TB-500 as “Thymosin beta-4, fragment (LKKTETQ), also known as TB-500.” It was on FDA’s “Category 2” list of bulk ingredients that may pose significant safety risks in compounding. By April 22, 2026, the nominations were withdrawn; FDA still lists its safety concerns and notes it has found no human exposure data.⁸

FDA review and advisory vote. In May 2026, FDA’s scientists recommended against adding TB-500 to the 503A bulks list, the list of ingredients that state-licensed pharmacies can use in compounding. They cited gaps in product characterization, no history of compounding use and no human safety or effectiveness data.¹ An FDA advisory committee narrowly voted in July 2026 to recommend adding TB-500; FDA’s own reviewers had recommended against it, and the vote is not binding. The vote was reported as 8–6 with 1 abstention, and it covered wound healing only.⁹¹⁰ FDA has posted no minutes.¹¹

2026 HHS draft policy. According to law-firm summaries of the draft policy, it covers six peptides: BPC-157, TB-500, KPV, MOTS-c, epitalon and semax.¹²¹³ As of 13 Nov 2026, HHS has published a draft, non-binding policy saying it does not intend to take enforcement action against licensed pharmacies compounding these peptides in certain forms.¹⁴ This is not FDA approval, and FDA has not added them to its official list.

The same summaries say the TB-500 form named is an injection under the skin or into a muscle. Conditions they describe include an FDA-registered ingredient source with a certificate of analysis, a single active ingredient, reporting of serious side effects and a patient-specific prescription.¹²¹³ The policy does not cover larger outsourcing facilities (503B).¹² As of November 13, 2026, a final policy had not been published. Check the Federal Register notice for updates.¹⁴

Most TB-500 sold online is labeled “for research use only.”¹ Those products are not made or checked as medicines. See our guides to research chemical peptide risks and Florida peptide rules.

Sport. WADA’s 2026 Prohibited List bans “Thymosin-β4 and its derivatives e.g. TB-500” at all times, under class S2 (growth factors).¹⁵

Common side effects and safety

• TB-500: unknown. Human safety has never been studied. FDA’s adverse-event database had no TB-500 reports through March 2025. A separate FDA complaint database had 2 reports involving blended TB-500 and BPC-157, with no safety assessment.¹
• Injected peptides. FDA is concerned that injected TB-500 may cause immune reactions, made worse by clumping and impurities.¹
• Thymosin beta-4 trials. Side effects were mild to moderate. The most common one with eye drops was mild stinging on use. No serious side effects were reported in these short studies.³⁷
• A theoretical cancer question. At the July 2026 meeting, a committee member raised a concern that thymosin beta-4’s normal functions might overlap with tumor growth and spread. No human data address this.⁹
• Blends. TB-500 is often sold mixed with BPC-157. When a reaction happens, it is hard to tell which ingredient caused it.

If you have used TB-500 and notice any symptom that worries you, tell a licensed provider.

Typical cost range

There is no reliable price data. TB-500 is not an approved product, so it has no official list price, and no published cost analysis was found. Cost depends on the source, whether it is blended with other peptides, and clinic visit or lab fees. Prices vary between clinics and pharmacies. Ask any provider for a written price breakdown before you start.

Our Polk County cost guide covers what to ask about pricing.

Questions to ask a provider

• Is this product TB-500 or full-length thymosin beta-4? How do you know?
• Which state-licensed pharmacy makes it, and does it meet the current HHS policy conditions?
• Since TB-500 has never been studied in people, why do you recommend it for me?
• Is it mixed with BPC-157 or anything else?
• What better-studied options should I try first?
• What side effects should I watch for, and how do I reach you?
• I play a sport that drug-tests. Does the WADA ban affect me?
• What is the total cost, and what does it include?

See also our guides on compounded vs FDA-approved peptides and how to vet a peptide clinic.