One study in eighty is about TB-500 itself. The other seventy-nine are mostly about thymosin β4, a different molecule roughly five times its mass — and mass spectrometry is the one check that tells you which of the two arrived.
TB-500 sits in the tissue repair and healing peptides category, and this platform keeps TB-500 and thymosin β4 as separate compound pages rather than one page with an alias, for the reason this article is about. The evidence picture is in TB-500 and thymosin beta-4: why 1 in 80 studies is about the compound you're buying; this page is about the vial and the label. For per-injection volume there is the BPC-157 + TB-500 calculator.
What is TB-500, and why does source quality matter?
TB-500 is a synthetic seven-amino-acid fragment, Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln, CAS 885340-08-9, formula C₃₈H₆₈N₁₀O₁₄, molecular weight 889.01 Da. It corresponds to residues 17–23 of thymosin β4, a 43-amino-acid endogenous protein of 4,963.44 Da. Source quality matters because the two are sold interchangeably under both names, and almost all the research cited on TB-500 product pages was done on the parent protein rather than the fragment in the vial.
TB-500 | Thymosin β4 | |
|---|---|---|
What it is | Synthetic fragment | Endogenous protein |
Sequence | Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln (Ac-LKKTETQ) | Ac-SDKPDMAEIEKFDKSKLKKTETQEKNPLPSKETIEQEKQAGES |
Length | 7 amino acids | 43 amino acids |
CAS | 885340-08-9 | 77591-33-4 |
Formula / MW | C₃₈H₆₈N₁₀O₁₄ / 889.01 Da | C₂₁₂H₃₅₀N₅₆O₇₈S / 4,963.44 Da |
Reference | ||
Studies (2026 review, n=80) | 1 | 70 |
The relationship between them is exact and checkable: residues 17–23 of thymosin β4 are L-K-K-T-E-T-Q — precisely TB-500. The fragment is formally Ac-Tβ4(17-23), the actin-binding motif lifted out of its parent protein. That is a real chemical relationship, and it is the basis of a reasonable hypothesis. It is not evidence of equivalence, and about one-fifth the length and one-fifth the mass is not a rounding difference.
The commercial consequence is the sourcing risk. A 2026 scoping review included 80 studies, of which 70 were on thymosin β4 and exactly one was a direct TB-500 study — and that one was a metabolite-profiling and fibroblast-screening exercise, not a healing trial. The same review found no human interventional study of either compound in tendon, ligament, muscle, bone or cartilage, which is what nearly everyone buys TB-500 for. So a vendor with no incentive to distinguish them, selling into a market that does not distinguish them, is under no commercial pressure to know which one is in the vial.
TB-500 has no discovery story of its own. It has no founding publication and no research programme; it entered the research-chemical market rather than the literature. Thymosin β4, by contrast, was identified by Prof. Allan Goldstein, who began thymosin work in 1964 at the Albert Einstein College of Medicine and continued at George Washington University. Everything that sounds like heritage on a TB-500 product page belongs to the other molecule.
What is the regulatory status of TB-500?
TB-500 is not approved for human use by the FDA, EMA or TGA, and as of August 2026 no compounding route exists. At the Pharmacy Compounding Advisory Committee meeting of 23–24 July 2026 the committee voted 8–6 with one abstention to recommend TB-500 for the 503A bulks list — advisory and non-binding, with rulemaking projected for 2027 or later and nothing yet added. WADA prohibits it at all times under S2.3, which names it explicitly.
Because no compounding route exists, this page has no compounded-TB-500 section. There is no approved product to copy and no 503A or 503B pathway to compare with research-grade supply, so the only question a buyer can actually act on is what is in the vial.
The gap between "an advisory committee recommended" and "the FDA approved" is where most of the misreporting sits. A narrow committee margin is a signal about deliberation, not a change in status. Our FDA peptide regulation timeline tracks where each nomination actually stands.
The sport ban is worth reading closely, because it is unusually specific. Both compounds are prohibited at all times on the 2026 WADA Prohibited List under S2.3, Growth Factors and Growth Factor Modulators, which names "Thymosin-β4 and its derivatives e.g. TB-500." That is a named-category prohibition rather than an inference from a catch-all clause. Note that the WADA entry does the thing this article argues against — it treats TB-500 as a derivative of Tβ4 — and for prohibition purposes that is the correct call, because both are banned. For evidence purposes it is not.
Claim you will meet while shopping | What the record says | Verdict |
|---|---|---|
"The FDA backed TB-500 in July 2026" | 8–6–1 advisory recommendation; no rulemaking completed | False |
"TB-500 does what thymosin β4 does" | 1 of 80 studies is on TB-500; equivalence never tested | Assumed, not shown |
"Proven to repair cardiac tissue" | Real — animal studies, thymosin β4 | Animal, parent protein |
"Promotes angiogenesis and cell migration" | Real mechanism — thymosin β4, the sequestering protein | Parent protein |
"Safe in humans, Phase 1 data exists" | Phase 1 was IV recombinant Tβ4 at µg/kg, not subcutaneous TB-500 | Wrong molecule, wrong route |
"Accelerates tendon and ligament healing" | No human interventional study in any musculoskeletal tissue, for either compound | Unestablished |
"5–7 day half-life" | No source located; the only human PK is IV Tβ4 | Unsourced |
"Not banned, it's just a peptide" | Prohibited at all times under WADA S2.3, named explicitly | No |
How do you tell TB-500 from thymosin beta-4?
Mass spectrometry answers it outright, because the two candidate molecules differ by 4,074 Da: roughly 889 Da is TB-500, roughly 4,963 Da is thymosin β4. That gap is enormous on a mass spectrometry trace — far easier to resolve than the 16 Da separating other commonly conflated pairs — so there is no technical excuse for a vendor not knowing which compound it is shipping. Check the CAS too: 885340-08-9 against 77591-33-4.
A certificate reporting only a purity percentage has told you nothing about identity. HPLC reports what proportion of a sample is a single species; it does not report which species that is. On a pair separated by more than four thousand daltons, that distinction is the entire question — see mass spectrometry for peptides and how to read peptide lab test results for both traces side by side.
The second tell needs no laboratory at all. Watch for marketing that cites thymosin β4's cardiac or ophthalmic research while selling TB-500. The landmark cardiac paper is Bock-Marquette et al., published in Nature in 2004 — frequently miscited as Nature Medicine 2003 — and it reported that Tβ4 promotes myocardial and endothelial cell migration and improves cardiac function after coronary ligation in animals. That is the parent protein. A page that quotes it under a TB-500 heading has shown you its own conflation before you have opened anything.
The most informative human data points the same way, and it is routinely left out. Thymosin β4 was tested properly in people and mostly missed.
Trial | Indication | Size | Outcome |
|---|---|---|---|
Phase 1 (NL005) | Healthy volunteers, IV recombinant Tβ4 | 54 single-dose at 0.05–25 µg/kg; 30 over ten days | No dose-limiting toxicities, no serious adverse events |
SEER-1 | Neurotrophic keratopathy | 18 patients | 6/10 vs 1/8 healed; primary endpoint missed (Fisher's exact, p=0.0656) |
ARISE-1, -2, -3 | Dry eye disease | 1,600+ combined | Did not meet pre-specified co-primary endpoints |
More than 1,600 patients across three Phase 3 trials, and the parent protein did not clear its endpoints. That is the strongest signal anyone has about this molecule class in humans, and it points the opposite way from how the fragment is marketed.
7 things to check before ordering TB-500
Seven checks cover TB-500, and four of them are about identity rather than purity, because identity is where this compound actually fails. Mass spectrometry at 889 Da, the CAS printed on the label, the seven-residue sequence and its acetyl cap on the spec sheet, the research the product page cites as evidence, third-party HPLC from a named laboratory, net content and endotoxin on the same batch, and an honest account of what none of it can establish.
Mass spectrometry at a mass near 889 Da. This is the check, and on this compound it is unusually decisive: 889 Da against 4,963 Da is a 4,074-dalton gap that any mass spectrometer resolves trivially. Insist on a batch-matched result rather than a specimen certificate from an earlier lot. A CoA with a purity percentage and no mass result has not addressed the only question that matters here.
The CAS number on the label. 885340-08-9 is TB-500; 77591-33-4 is thymosin β4. A vendor printing neither, or printing one that matches neither compound, has told you the listing was assembled from other listings. This is the cheapest identity signal available and it costs nothing to check.
The sequence and the acetyl cap on the spec sheet. TB-500 is Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln — seven residues, N-terminally acetylated, C₃₈H₆₈N₁₀O₁₄. A 43-residue sequence printed under a TB-500 heading is the parent protein. An unacetylated seven-mer is not the compound the market means by TB-500 either, since the acetyl group is part of the formal designation Ac-Tβ4(17-23).
The research the product page cites. Cardiac repair, angiogenesis, wound healing and the entire ophthalmic programme belong to thymosin β4, the 43-residue protein. If the citations under a TB-500 listing are Goldstein's mechanism work, Bock-Marquette's Nature paper or RegeneRx's RGN-259 trials, the seller is selling one molecule on another molecule's evidence. This check requires no laboratory and no purchase.
Third-party HPLC purity from a named laboratory. Purity is compound-specific and moves as new certificates are indexed, so read it live against the Purity Index rather than against a vendor's stated house standard. A vendor's own document is a claim; an independent result from a named lab is a measurement.
Net peptide content and an LAL endotoxin result on the same batch. Purity and quantity are separate axes — a 99% pure vial can be substantially underfilled, which is what net peptide content measures. Endotoxin is a third axis again, and an absent LAL result means the batch was not tested rather than that it passed.
What no certificate can establish. A perfect CoA confirms that a vendor shipped a seven-residue peptide at the stated quantity. It cannot tell you that the peptide does anything, because no human interventional study of TB-500 exists in tendon, ligament, muscle, bone or cartilage; the human safety data belongs to intravenous recombinant Tβ4 dosed in µg/kg while community protocols run to 2–4 mg per week subcutaneously; and the parent protein missed its endpoints in more than 1,600 Phase 3 patients.
Check | What it confirms | How to verify | Red flag |
|---|---|---|---|
Mass spectrometry | Which molecule you have — ~889 Da (TB-500) vs ~4,963 Da (Tβ4) | Batch-matched CoA with the MS result | Purity reported with no identity test |
CAS on the label | The vendor knows which one it sells | 885340-08-9 vs 77591-33-4 | Neither number given, or one matching neither |
Sequence and acetyl cap | It is the fragment, not the protein | Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln, 7 residues, C₃₈H₆₈N₁₀O₁₄ | A 43-residue sequence printed under a TB-500 heading |
Research cited on the product page | Whether the seller distinguishes the two | Cardiac, angiogenic and ophthalmic results belong to thymosin β4 | Nature 2004 cardiac work quoted to sell a 7-mer |
HPLC purity | Proportion of intended peptide | Third-party CoA from a named lab, read live | Vendor's own document only |
Net peptide content | Peptide versus salts and water | Net content or amino acid analysis figure | Purity quoted as though it were quantity |
Endotoxin (LAL) | No pyrogens in injectable material | LAL result on the batch | Not tested, not mentioned |
Because the mass gap is so large, there is no technical excuse for a vendor not knowing which compound it is shipping. That makes TB-500 unusual in this cluster: the identity problem is severe and the identity test is easy. Everything expensive about verifying this compound is a choice the seller made.
Where does TB-500 rank on Peptigrity's lab test database?
Peptigrity tracks 530 shops and 11,852 independent lab tests across 118 peptides, with 1,283 community reviews (verified August 2026), and weights community reviews and independently verified HPLC purity equally at 50% each in every trust score, with no financial relationship influencing the ranking. TB-500's own purity figure, test count and per-milligram prices are read live from the Purity Index and price pages rather than fixed on this page, because both move as new certificates and offers are indexed.
That is a deliberate choice rather than a gap, and it matters more on this compound than on most. A purity number quoted in prose ages; a number read live does not. Individual results are searchable in the lab test database, and per-compound purity and test counts sit on the TB-500 compound page — which is separate from the thymosin β4 page precisely so that certificates for one molecule are not pooled with the other.
On price, TB-500 price data publishes shops in stock, median and lowest price per milligram with the vial size behind the lowest figure, and is the current source for cost comparisons. Read it within a single vial-size band, since fixed per-vial costs push the per-milligram figure down as fill size rises, which makes a large vial look like a better product rather than a bigger one. Those figures exclude shipping, taxes and customs, coupon codes, bulk tiers, multi-vial kits and account-gated pricing.
One further pricing caution is specific to this compound. TB-500 is commonly sold blended with BPC-157, and a blend vial carries no separate identity result for either component unless the certificate reports both masses. The head-to-head is in comparing BPC-157 and TB-500, and the blend is tracked on the Wolverine blend page.
The trial that would settle this is not a testing study, and on TB-500 the shortfall is unusually easy to specify: nobody has run the study on the molecule people actually buy.
Element | Requirement | Why |
|---|---|---|
Compound | TB-500 specifically, not thymosin β4 | 1 of 80 studies has done this; equivalence is assumed, not demonstrated |
Design | Randomised, double-blind, placebo-controlled | Injury recovery has a strong natural-history confound |
Population | One defined tendinopathy | The literature spans cardiac, ophthalmic and dermal models that cannot be pooled |
Route and dose | Subcutaneous, with PK sampling | The only human PK is IV recombinant Tβ4 at µg/kg |
Endpoint | Imaging plus validated function score | Subjective improvement cannot separate treatment from natural recovery |
Comparator | Progressive loading, the standard of care | Beating placebo is not the useful question |
That last row is not a joke. For tendinopathy — the most common reason people buy TB-500 — progressive mechanical loading has the strongest human evidence of anything in this field, and it is free of both the identity problem and the attribution problem. See peptides for joint health, cartilage and tendon repair for where peptide claims sit against it.
Frequently Asked Questions
What purity standard should TB-500 meet?
Read it live rather than against a fixed threshold. Per-compound purity moves as new certificates are indexed, so the useful comparison is TB-500's current figure on the Purity Index against the platform composite, not a vendor's "above 98%" promise. On this compound, however, purity is the second question — an identity result at 889 Da comes first.
How much does TB-500 cost?
The price page publishes shops in stock, median and lowest price per milligram, with the vial size behind the lowest figure. Compare within one vial-size band, because fixed per-vial costs fall away as fill size rises and make larger vials look cheaper per milligram than the product warrants.
Did the July 2026 FDA vote make TB-500 legal?
No. The 8–6–1 recommendation is advisory. FDA has not completed rulemaking, is not required to follow it, and nothing has been added to the 503A bulks list. TB-500 remains unapproved by the FDA, EMA and TGA, and prohibited in sport at all times under WADA S2.3.
How do I know which molecule is in my vial?
Mass spectrometry. Roughly 889 Da is TB-500; roughly 4,963 Da is thymosin β4. The 4,074-dalton gap is unmistakable on a trace, and the CAS numbers separate them on paper: 885340-08-9 against 77591-33-4.
What dose of TB-500 is supported by evidence?
None. No published study supports any community protocol. The only human pharmacokinetic data for this molecule class is intravenous recombinant thymosin β4 dosed in µg/kg, while community TB-500 protocols run to 2–4 mg per week subcutaneously — a different molecule, a different route, and roughly three orders of magnitude of difference in exposure.
Thymosin β4 missed its endpoints in over 1,600 patients — does that apply to TB-500?
Not directly, and that is the problem. The Phase 3 failures belong to the parent protein in an ophthalmic indication, so they do not transfer to a seven-residue fragment in tendon any more than the positive animal cardiac results do. The read-across runs both ways, and TB-500 is marketed on only one direction of it.
Browse the tissue repair and healing peptides category, or our complete peptide guide with 118 compounds (verified August 2026). For reconstitution and per-injection volume, use the BPC-157 + TB-500 calculator alongside the reconstitution calculator. Compare shops through independent lab tests and community-verified shop reviews.
This article is for educational and informational purposes only and does not constitute medical advice. Peptides discussed may be investigational compounds not approved by the FDA (or equivalent regulators in your jurisdiction) for human use. Always consult a qualified healthcare provider before using any peptide or research compound. Peptigrity is an independent review platform and does not sell, endorse, or recommend specific products or vendors
