Compound guide · Tier D
TB-500
The clearest example on this site of a real research programme being used to sell a different molecule. The human trials were of thymosin beta-4. TB-500 is a fragment of it.
The short answer
Almost every claim made for TB-500 is borrowed from thymosin beta-4, which is a different substance. Thymosin beta-4 is a 43 amino acid protein that has genuinely been through human trials, in dry eye disease, corneal injury and pressure ulcers. TB-500 is a short synthetic fragment of that sequence sold as research material. The fragment has not been through those trials. Reading a thymosin beta-4 result and buying TB-500 is not a small approximation, it is a substitution of one molecule for another, and the vendor literature almost never makes the distinction.
At a glance
| Class | Synthetic fragment of thymosin beta-4 |
| Developer | No developer. The related full length peptide, thymosin beta-4, was developed by RegeneRx Biopharmaceuticals. |
| Sold as | None. Sold only as research material. |
| Regulatory status | Not approved by any regulator, anywhere, for any indication in humans or animals. There is no marketing authorisation for TB-500 from the FDA, the EMA, the MHRA, the TGA or SAHPRA. |
| Compounding status | The FDA removed TB-500 from the 503A Category 2 bulk substances list in April 2026, alongside eleven other peptides. That is a change to a compounding classification and nothing more. It is not marketing authorisation, it involved no efficacy review, and TB-500 remains an unapproved drug. |
| Anti-doping | Prohibited at all times under S2. TB-500 is explicitly named in WADA guidance. |
| Our evidence tier | Tier D. Preclinical evidence only |
What it is
Thymosin beta-4 is a naturally occurring 43 amino acid protein involved in actin binding, cell migration and wound repair. TB-500 is a synthetic peptide corresponding to a short active region of that protein, most commonly described as the actin binding domain. The commercial argument is that the fragment reproduces the useful part of the parent protein. That is a hypothesis about the fragment, and it is not the same as evidence for the fragment.
Who it is for, and who actually takes it
Nobody, in the regulatory sense. There is no approved population because there is no approval. The human research that exists was conducted with thymosin beta-4 in ophthalmic and wound healing settings, under trial conditions, and none of it produced a licensed product.
It is bought overwhelmingly for soft tissue injury, tendon and ligament recovery and general healing, usually stacked with BPC-157. The rationale is animal data and anecdote. There is no controlled human trial of TB-500 for any musculoskeletal injury.
What the research shows
There is no controlled human trial of TB-500 to chart. Presenting animal data as a bar chart alongside our human trial charts would imply a parity that does not exist, so we publish the absence instead.
Dosing
We publish no dosing for TB-500 and there is none to publish. No regulator has approved a dose, and no controlled human trial of TB-500 has established one. The schedules circulating on vendor pages and forums are not derived from human data on this molecule. Where a number is attached to a thymosin beta-4 trial, it belongs to a different peptide given by a different route for a different indication.
What happens when you come off it
There is no discontinuation data, because there is no controlled human administration data to discontinue from. Anyone describing what happens when you come off TB-500 is describing anecdote.
What it is being studied for
| Area | Stage of evidence |
|---|---|
| Soft tissue and tendon injury | Preclinical only, animal models |
| Cardiac repair after infarction | Preclinical, thymosin beta-4 rather than TB-500 |
| Dry eye disease | Human trials, thymosin beta-4, not TB-500 |
| Corneal wound healing | Human trials, thymosin beta-4, not TB-500 |
| Pressure ulcers and wound repair | Human trials, thymosin beta-4, not TB-500 |
| Hair growth | Preclinical only |
Read that table carefully, because it is the whole argument. Every row with human data names thymosin beta-4. Every row naming TB-500 is preclinical. That is the distinction the marketing collapses.
Common myths
TB-500 has been through human clinical trials.
It has not. Thymosin beta-4 has. They are different molecules, and the trials that exist used the full length protein, largely by topical or ophthalmic routes rather than by injection for injury repair.
The FDA delisting in April 2026 means TB-500 is now allowed.
It means TB-500 came off a compounding classification list. It is not an approval, no efficacy review took place, and TB-500 remains an unapproved drug that no regulator has authorised for human use.
It is safe because thymosin beta-4 occurs naturally in the body.
TB-500 is not thymosin beta-4, and endogenous origin would not establish the safety of supraphysiological doses by a route the body does not use in any case. This inference appears on nearly every vendor page selling it and is not supported by intervention data.
It is proven to heal tendons because athletes use it.
Use is not evidence, and the population using it is precisely the population least able to run a controlled comparison on themselves. TB-500 is also prohibited in tested sport at all times under WADA S2.
Verifying a purchase
TB-500 is a short peptide, which makes it cheap to synthesise and easy to substitute. The specific risk here is not usually contamination but identity: confirm by mass spectrometry that you have the fragment described and not a different short peptide or the full length protein. Insist the report carries the batch code on your vial. A high HPLC purity figure on an unnamed peptide tells you the vial contains one thing consistently, not that it contains the right thing.
The general method is set out in our guide to reading a certificate of analysis, which covers the eleven checks that apply to any compound. The points above are the ones specific to TB-500.
Caveats and safety
There is no human safety database for TB-500. That is not a statement that it is dangerous, it is a statement that nobody knows, which is a different and in some ways worse position. Thymosin beta-4 promotes angiogenesis and cell migration, and the theoretical concern that follows, about effects on existing malignancy, has never been resolved in humans for either molecule.
Where to get it
Where to get it
CertaPeptides Romania, EU. Volume discounts at 3+, 5+ and 10+ units.
| Vial | Price |
|---|---|
| 2 mg | €31.49 |
| 5 mg | €44.49 |
| 10 mg | €84.99 |
| 20 mg | €163.49 |
Stated purity. ≥98% stated batch specification. Published lot report #212152 returned 98.97% on a 10 mg vial, with 10.87 mg measured against a 10 mg label, which is 108.7% of the stated content.
Documentation. Selected lots independently tested by Janoshik Analytical (Czech Republic), HPLC plus mass spectrometry, reports searchable on the Janoshik public portal and at certapeptides.com/verify.
TB-500 is sold as laboratory research material. The vendor states it is not for human consumption and that it is not approved by the FDA, the EMA or any other regulator for use in humans or animals. Read the evidence tier at the top of this page before the price.
View TB-500 at CertaPeptidesAffiliate link. We earn a commission if you buy, at no extra cost to you. It does not change a word of the assessment above. Every product we have priced, in one list.
Sources
- FDA bulk drug substances nominated for use under section 503A
- WADA Prohibited List, section S2
- Registered thymosin beta-4 trials, ClinicalTrials.gov
- Thymosin beta-4 literature, PubMed
Related compounds
Disclosure. PeptoPurity is an affiliate of CertaPeptides and earns a commission on qualifying purchases made through the vendor link on this page, at no additional cost to you. That relationship does not set the evidence tier, alter the verdict, or change a word of the assessment. Our Tier C and Tier D pages carry the same links as our Tier A pages, with the same conclusions we would publish if we earned nothing. Where the registered, prescribed route is the better option, we say so on the page that would otherwise pay us.
Scope. This is an evidence review, not medical advice. Where an approved label schedule is reproduced it is a record of what a regulator has published about a licensed medicine, not a recommendation and not a schedule for anyone to follow unsupervised. For unapproved compounds we report only the doses used in published studies, attributed to those studies, and we publish no protocols and no reconstitution guidance for any compound. Regulatory status differs between countries and changes over time. Material sold for laboratory research is not approved for human use. Decisions about treatment belong with a qualified prescriber.