Identity and evidence record · C-010
TB-500 and thymosin beta-4: evidence and naming
The two names are not interchangeable. TB-500 is commonly used for a short synthetic fragment related to thymosin beta-4. Evidence about the full-length protein cannot automatically establish what the fragment does.
TB-500 and full-length thymosin beta-4 are different substances, although seller pages often blur them. Repair claims for TB-500 rely mainly on preclinical reasoning and evidence borrowed from the full-length protein. The FDA found no adequate human TB-500 evidence for wound healing and insufficient information to establish safety.
What the names refer to
The distinction changes which research can answer the claim.
| Term | What it describes | Why it matters |
|---|---|---|
| Thymosin beta-4 | A naturally occurring 43-amino-acid peptide that has been studied as a full-length investigational product. | Its pharmacology, formulation and clinical observations concern that full-length substance. |
| TB-500 | A common name for a synthetic seven-amino-acid fragment corresponding to thymosin beta-4 residues 17–23, usually described with an N-terminal acetyl group. | The fragment is not the same chemical substance as the 43-amino-acid protein. |
| TB-500 acetate | A salt form distinct from the free base. Public naming and records may not state the form consistently. | Form, sequence and modification affect identification, reference matching and interpretation. |
Claim-level evidence
Similar language does not create transferable evidence.
Soft-tissue or wound repair with TB-500
Preclinical and indirect evidence. Biological arguments often draw on thymosin beta-4 research or fragment experiments. The FDA’s 2026 review found no human studies adequate to assess TB-500 for wound healing.
TB-500 is “the same as” thymosin beta-4
Contradicted by substance identity. The common TB-500 fragment is seven amino acids long. Full-length thymosin beta-4 is 43 amino acids. They may be related, but they are not the same substance.
Human safety inferred from full-length thymosin beta-4
Not transferable without evidence. A phase 1 study reported tolerability findings for full-length intravenous recombinant thymosin beta-4 in healthy participants. It did not test TB-500, a consumer product, or the intended conditions behind online repair claims.
Identity and quality of a seller’s vial
Unknown unless item-specific evidence establishes it. Sequence, form, quantity, related impurities, sterility and endotoxin require suitable methods and a traceable sample link.
Why full-length evidence cannot be borrowed
A molecule’s length and chemical modifications affect structure, metabolism, distribution and biological activity. A fragment may share part of a sequence without sharing the full-length protein’s behaviour or clinical evidence.
The 2021 phase 1 paper involved recombinant human thymosin beta-4 given intravenously under a controlled protocol. It reported no serious adverse events in the study population. That result cannot establish the safety of TB-500, different forms, repeated consumer use or a vial from an unknown supply chain.
The burden is on the TB-500 claim to provide TB-500 evidence. Similar names, shared residues and vendor citations are not substitutes.
Research record added 6 September 2026. The 2026 sports-medicine review is covered in our injury-recovery literature update. Keep the substance distinctions on this page when following that review.
What identity testing must resolve
A useful identity assessment needs the expected sequence and chemical form, suitable reference information and a method capable of distinguishing the target from related material. A mass result may support molecular identity, but it still needs interpretation and sample provenance.
Chromatographic purity answers a separation question. It does not by itself establish the name of the main peak, amount in the vial, sterility, endotoxin, stability or clinical suitability. The FDA’s public representative certificate for a TB-500 nomination contained identity and purity information but lacked several other quality attributes needed for a complete assessment.
Read how identity testing handles fragments and keep the substance name, salt form and sample link visible.
Sport status
The 2026 WADA Prohibited List includes thymosin beta-4 and its derivatives, including TB-500, in section S2. The rule applies in and out of competition. A product’s label, claimed research status or uncertain composition does not remove anti-doping risk.
See what this means if you compete. Athletes remain responsible for substances found in their samples, and mislabelling can add uncertainty rather than protection.
How we assessed this record
We treated naming as an evidence question, not a wording detail.
Define the substance
Separate full-length thymosin beta-4, the TB-500 fragment and stated salt forms.
Match the study
Record exactly which substance, formulation, route and population a paper tested.
Assess the claim
Prioritise direct controlled human outcomes over mechanistic and animal evidence.
Assess the product
Keep label, certificate, independent test and scientific literature as separate layers.
Source ledger
Primary and peer-reviewed sources checked on 7 August 2026.
- FDA TB-500 briefing document, July 2026 · substance identity, naming, quality evidence and assessment of human use.
- Ac-SDKP fragment research record · chemistry and experimental context for the short thymosin beta-4 fragment.
- Phase 1 study of full-length recombinant thymosin beta-4 · human tolerability evidence for a different substance and formulation.
- FDA safety-risk list for compounded bulk substances · absence of adequate human TB-500 exposure and safety information.
- World Anti-Doping Agency 2026 Prohibited List · current classification of thymosin beta-4 and derivatives.
Follow the adjacent evidence
Questions people ask
Are TB-500 and thymosin beta-4 the same thing?
No. TB-500 commonly refers to a seven-amino-acid synthetic fragment related to thymosin beta-4. Full-length thymosin beta-4 contains 43 amino acids. Related sequences do not make them the same chemical substance.
Is there human evidence that TB-500 heals injuries?
The FDA’s 2026 review found no adequate human TB-500 studies for wound healing. Human research on full-length thymosin beta-4 cannot be counted as direct evidence for the TB-500 fragment.
Is TB-500 prohibited in sport?
Yes. The 2026 WADA Prohibited List includes thymosin beta-4 and its derivatives, including TB-500, in S2. They are prohibited at all times, both in and out of competition.
Can a purity result distinguish TB-500 from thymosin beta-4?
Not by percentage alone. The main peak must be identified with a suitable method and reference. The expected sequence, modification and form must also match, and the sample must be traceably linked to the item.
Evidence library
Claim-level evidence records
Open the individual records behind this profile. Each record links to the primary and official sources used for its verdict.
Profile-to-record links checked 10 August 2026. These evidence records received named scientific and clinical sign-off on 10 August 2026.
Editorial experience
From our work: how we checked this page
For topical-map item C-010, TB-500 and thymosin beta-4: evidence and naming was checked as a distinct editorial task, not treated as a generic peptide page. We reviewed 5 unique external sources and 8 internal destinations in the page, then checked that the opening answer, headings, source descriptions and linked next steps stayed within the same claim boundary. The count records links in the published page and is not a claim that every source carries equal evidential weight.
Eleni Kiromitis checked study design, biomedical evidence, evidence directness and laboratory context. Dr Stavroula Nikitopoulou checked clinical claims, adverse effects, contraindications, red flags and patient-facing safety wording. Each reviewer stayed within the remit published on the governance page. Yianni Kiromitis retained responsibility for source verification, editorial decisions and correction management.
We did not use patient experience, a personal treatment outcome, seller testimony or an assumed product identity to support this page. The publication did not independently test a vial for this review. Where a page refers to a laboratory result, that result applies only to the named sample, method and attribute. We kept uncertainty beside the conclusion, recorded which source supports each material claim, and checked that the visible review date matches the publication record. A new controlled study, regulator update, corrected source, analytical report or credible safety signal can trigger reassessment through the public correction route.
Research reference checked and reviewed · 6 September 2026. Scientific review: Eleni Kiromitis. Clinical review: Dr Stavroula Nikitopoulou. The existing evidence verdict is unchanged; earlier sources retain their own check dates.