TB-500 is the research-market name for synthetic thymosin beta-4, a 43-amino-acid peptide that binds actin and regulates cell migration during tissue repair, or for one of its shorter active fragments. Which of those you receive depends on the vendor, because the same product name is applied to the full peptide and to fragments such as residues 17-23. Published research is preclinical and there is no approved TB-500 product. An FDA advisory committee recommended it for pharmacy compounding on 23 July 2026, which does not make it legal to compound. Across 28 third-party-tested single-compound vials we hold, median purity is 99.93% with none below 99%.
Research notes
The biggest problem with TB-500 is not purity. It is that "TB-500" does not name one molecule. Some vendors ship the full 43-residue thymosin beta-4 under that label. Others ship a short active fragment. In our own certificate corpus the material sold as TB-500 arrives under at least four different compound names. Before comparing two vendors on price, you have to establish that they are selling the same thing, and often they are not.
Once that is settled, the material itself tests well.
How does TB-500 work?
Thymosin beta-4 is a naturally occurring 43-amino-acid peptide. Its best-documented activity is binding G-actin, sequestering it and modulating actin-cytoskeleton dynamics. That matters for repair because actin remodelling is how cells physically migrate into a wound.
Reported secondary mechanisms include angiogenesis promotion and anti-inflammatory activity. The overall framing resembles BPC-157, which is why the two are so often sold as a pair, but the molecular targets are different. BPC-157's story is growth-factor and vascular signalling. TB-500's is cytoskeletal.
Published work on TB-500 itself is preclinical. Human trials exist only for the full-length protein (below).
What exactly are you buying when a vendor says TB-500?
This is the practical question and it has a measurable answer. Across our Kovera corpus, certificates for material sold as TB-500 carry these labels:
| Compound label on certificate | Records |
|---|---|
| TB-500 (Thymosin B4) | 23 |
| TB-500 (17-23) | 3 |
| TB-500 (43aa) | 1 |
| TB-500 | 1 |
| BPC-157 / TB-500 blend | 62 |
| Other blends containing TB-4 | 5 |
The full 43-residue peptide and the 17-23 fragment are not the same product and should not be priced against each other per milligram. A cheap TB-500 may be cheap because it is a seven-residue fragment rather than the full molecule.
The fix is boring and it works: read the compound field on the certificate, not the product title on the shop page.
Did the July 2026 FDA vote make TB-500 legal?
Update, 29 October 2026: HHS filed an interim enforcement-discretion policy (Federal Register, 30 October). It says HHS does not intend to act against 503A pharmacies and physicians compounding TB-500 acetate (the seven-residue fragment) for subcutaneous or intramuscular injection. The conditions include a patient-specific prescription, a single ingredient and API from a registered manufacturer. The policy is not a rule and does not cover research-use-only vials. Our HHS policy explainer lists all ten conditions.
No. On 23 July 2026 the FDA Pharmacy Compounding Advisory Committee voted 8-6 with one abstention to recommend TB-500 for the 503A Bulks List, nominated for wound healing. It had already come off the Category 2 do-not-compound list in April 2026, listed there as thymosin beta-4 fragment.
Neither step legalises compounding. FDA must complete notice-and-comment rulemaking, expected to reach 2027 or later, or grant interim Category 1 status. FDA's review scientists recommended against all seven peptides considered at that meeting. The full breakdown is in our FDA peptide vote explainer.
For research-grade TB-500 sold online, nothing changed at all.
How pure is the TB-500 on the market?
Across 28 single-compound TB-500 certificates issued by Kovera Labs, covering 24 vendors, certified between 7 February and 28 May 2026 and retrieved from Kovera's verifier on 2 August 2026:
| Measure | Single-compound | In BPC-157 blends |
|---|---|---|
| Records | 28 | 67 |
| Distinct vendors | 24 | 49 |
| Median purity | 99.93% | 99.77% |
| Lowest purity | 99.35% | 98.72% |
| Records below 98% | 0 | 0 |
| Identity confirmation failures | 0 | 0 |
| Vials under labelled content | 0 of 27 | 1 of 67 |
Single-compound TB-500 is among the cleanest categories we track, with no vial below 99.35% and none short on content. Blended vials sit slightly lower on both purity and floor, which is the expected pattern when four figures are collapsed into one.
Two caveats apply to every figure above. A certificate covers a tested batch, not your vial, so the lot numbers have to match. And Kovera revises certificates in place under the same reference number, so a certificate captured months ago may no longer match the lab's current record. Note the retrieval date, and check any certificate against the issuing lab through our COA verifier rather than trusting a vendor-hosted PDF. Our read on the lab is in is Kovera Labs legit.
Is TB-500 in human clinical trials?
Not as TB-500. The only registry record for the 17-23 fragment, NCT07487363, says in its own summary that it is a "fictional study". It is one of eight such registrations. The human trials that do exist use full-length thymosin beta-4, a different and much larger molecule:
| Trial | Phase, size | Status, 13 October 2026 |
|---|---|---|
| ARISE-3, RGN-259 eye drops for dry eye (ReGenTree) | Phase 3, 700 | Completed. Results posted 28 August 2026 |
| SEER-2, RGN-259 for neurotrophic keratopathy | Phase 3, 70 | Recruiting |
| NCT07586865, recombinant thymosin beta-4 (NL005) after heart attack | Phase 2, 189 | Not yet recruiting |
Results for the full protein, given as eye drops or a hospital infusion, say nothing about a seven-residue fragment injected from a research vial.
What this means
TB-500 tests clean and is sold ambiguously. The failure mode here is not a bad batch, it is buying a fragment while believing you bought the full peptide, or comparing two vendors on a per-milligram basis when they are shipping different molecules.
The July vote does not change what is in the vial or what you are allowed to do with it. It changes where the compound sits in a regulatory queue that has at least two more gates to clear.
Related reading
- FDA peptide vote 2026 - the vote tallies and the gates between a recommendation and legal compounding.
- BPC-157 - the compound TB-500 is most often paired with, recommended on the same day.
- KPV - also recommended on 23 July, and the cleanest compound in our corpus.
- GHK-Cu - the fourth KLOW component, off Category 2 in April but never put to a vote.
- KLOW stack research read - what a four-compound blend hides that four separate vials would not.
- BPC-157 and TB-500 stack - how the pairing is used and what the combined certificates show.
What it's researched for
- tissue repair and recovery research
- cell migration and angiogenesis research
- wound healing research
Where to source it
ALL 21 VENDORS →RANKED BY COMPOSITE SCORE · PRICES ARE SNAPSHOTS FROM THE PRICE INDEX · PER-MG IS A WITHIN-COMPOUND COMPARATOR
Frequently asked about TB-500
What is TB-500?
TB-500 is the research-grade name for a synthetic version of thymosin beta-4, a naturally occurring 43-amino-acid peptide that binds G-actin and participates in cell migration, angiogenesis and tissue repair. Vendors apply the name both to the full molecule and to shorter active fragments, which is a recurring source of confusion.
Is TB-500 the same as thymosin beta-4?
Not reliably. Some vendors sell the full 43-residue thymosin beta-4 under the TB-500 name, others sell fragments such as residues 17-23. In our lab corpus the certificates carry at least four different compound labels for what is sold as TB-500. Check the certificate for the specific molecule before comparing prices between vendors.
Is TB-500 FDA approved?
No. TB-500 is not approved for any human indication. On 23 July 2026 an FDA advisory committee voted 8-6 with one abstention to recommend it for the 503A Bulks List for wound healing. That recommendation requires notice-and-comment rulemaking before compounding becomes lawful. It is also banned by every major racing authority for veterinary use.
How does TB-500 work?
The documented mechanism is actin sequestration. Thymosin beta-4 binds G-actin and modulates actin-cytoskeleton dynamics, which controls how cells migrate into a wound during repair. Secondary reported mechanisms include angiogenesis promotion and anti-inflammatory activity. The framing overlaps with BPC-157 but the molecular target is different.
What doses are used in TB-500 research?
Commonly cited research-protocol figures are 2 to 5 mg twice weekly, or 2 to 10 mg weekly in a loading phase followed by a maintenance taper. Because the full peptide has a multi-day half-life, protocols use weekly or twice-weekly schedules rather than daily ones. These figures are market conventions, not published human protocols.
How pure is research-grade TB-500?
Across 28 single-compound Kovera certificates from 24 vendors, certified between February and May 2026, median purity was 99.93% with a floor of 99.35% and no identity failures. Blended BPC-157 and TB-500 vials tested slightly lower at 99.77% median across 67 records, which is the expected pattern for multi-component products.