TB-500 / Thymosin Beta-4 vs Thymalin
The distinction that mattersThe "thymus peptide" shelf holds three unrelated products and this is the third. Thymalin is an undefined bovine thymic extract registered only in Russia — not a single molecule at all — and shares nothing with thymosin beta-4 beyond the shelf it sits on. Treating them as a family means accepting an extract of unknown composition on the strength of a different peptide's trial record.
| TB-500 / Thymosin Beta-4 Research Use Only | Thymalin Limited Approval | |
|---|---|---|
| Evidence rating |
2/5 Limited
Evidence rating 2 out of 5: Limited
|
2/5 Limited
Evidence rating 2 out of 5: Limited
|
| Regulatory status | Full-length Tβ4 has reached phase 2/3 trials for dry eye and corneal wounds. The injectable TB-500 fragment sold to consumers is unapproved. WADA-prohibited. | Registered in Russia as an immunomodulator. Not approved in the US, EU or UK. |
| Category | Healing & Tissue Repair | Immune & Anti-inflammatory |
| Drug class | Thymosin beta-4 is a 43-amino-acid actin-sequestering protein; TB-500 is a synthetic active fragment | Polypeptide complex extracted from calf thymus — a mixture, not a single molecule |
| Route | Every registered systemic human study used the intravenous route with the intact 43-residue protein; the eye trials were topical drops. The subcutaneous and intramuscular injection of the TB-500 fragment that the consumer market runs on has no human pharmacokinetic study behind it. | Intramuscular |
| Half-life | Full-length Tβ4 ~0.5–2 hours intravenously in healthy volunteers; the LKKTETQ fragment actually sold has no published pharmacokinetics. | Not applicable — heterogeneous mixture |
| Sequence length | 43 residues | Mixture — no single sequence |
| Molecular weight | 4,963.5 Da | — |
| Studied in | Randomised topical trials of full-length Tβ4 in the eye: ARISE-1, ARISE-2 and ARISE-3 in dry eye, and a neurotrophic keratopathy programme (SEER-1 closed early, SEER-2 recruiting, the European SEER-3 missing its primary endpoint). Phase 2 dermal wound trials in venous stasis and pressure ulcers, with the epidermolysis bullosa and diabetic corneal wound trials terminated. Intravenous phase 1 studies of the intact protein in healthy volunteers, and randomised phase 2 cardiac trials of recombinant Tβ4 after myocardial infarction. The marketed TB-500 heptapeptide entered its first registered human trial in 2026, in stable atherosclerotic disease with biomarker endpoints. | Russian clinical studies in immunodeficiency and post-surgical infection; a long-term gerontology cohort study reporting mortality reduction in elderly participants. |
| Who should avoid it |
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| Legal status | Ophthalmic Tβ4 remains investigational. Injectable TB-500 is unapproved and not lawfully sold for human use. | Registered in Russia; unapproved elsewhere. |
Benefits — TB-500 / Thymosin Beta-4
- Corneal wound healing evidence in humans
Ophthalmic trials of full-length Tβ4 reported improved corneal healing and dry-eye symptom scores — genuine randomized human data.
- Cell migration and angiogenesis
Well-characterised molecular biology supporting a role in wound repair.
- Anti-inflammatory and antifibrotic signals
Preclinical models show reduced scarring and inflammatory mediator expression.
- Cardiac repair in animal models
Promotes epicardial progenitor activation after myocardial infarction in rodents.
- A randomised human cardiac trial now exists — and it was negative overall
A double-blind, placebo-controlled trial of 96 patients with ST-elevation myocardial infarction after primary PCI tested recombinant full-length thymosin beta-4 against placebo, with infarcted area at 90 days as the outcome. The overall comparison was not statistically significant. A reduction was reported in the 43 patients who received their first dose within eight hours of PCI, and the authors themselves conclude that further rigorous randomised studies are needed to assess early use. That is a timing hypothesis, not a result, and it belongs to the intact 43-residue protein given intravenously — not to an injected fragment.
Benefits — Thymalin
- Reported immune restoration
Russian studies describe normalisation of lymphocyte subsets in immunodepressed patients.
- Long-term mortality signal
A multi-year cohort study reported reduced mortality in treated elderly subjects. The study design and independence are significant caveats.
- Long clinical use history
Decades of use in Russian practice without prominent safety signals reported.
Risks & cons — TB-500 / Thymosin Beta-4
- Injectable fragment is untested in humans
The systemic TB-500 sold online has no clinical trial support for musculoskeletal healing.
- Angiogenesis and tumour concern
Tβ4 is upregulated in several cancers and promotes tumour cell migration in laboratory models. Systemic chronic use in anyone with cancer risk is a real concern.
- No established systemic dosing or safety
Ophthalmic trials say nothing about the safety of injecting it for months.
- Unregulated supply
Research-chemical market quality problems apply.
- Named on the WADA Prohibited List, with a whole-squad precedent
Not a grey area and not an inference. "Thymosin-β4 and its derivatives, e.g. TB-500" were added as explicit examples of prohibited growth factors under S2.3, a class prohibited at all times, in and out of competition, and treated as non-specified — so the default sanction is the long one, and strict liability means intent is not a defence. The best-documented case is the Essendon Football Club supplements programme: in January 2016 the Court of Arbitration for Sport upheld WADA's appeal and found to its comfortable satisfaction that 34 past and present players had used thymosin beta-4, imposing two-year ineligibility periods backdated to March 2015 and costing most of them the entire 2016 season. Anyone in a tested sport, or in a military or law-enforcement programme that has adopted the WADA categories, is risking a career rather than a fine.
Risks & cons — Thymalin
- Undefined composition
An extract rather than a defined molecule, so batch consistency and mechanism attribution are both uncertain.
- No independent replication
The evidence base traces almost entirely to one research tradition and has not been reproduced elsewhere.
- Bovine biological source
Theoretical transmissible agent concerns and hypersensitivity risk from animal-derived protein.
- Autoimmune and transplant contraindications
Immune stimulation is inappropriate in autoimmune disease and after transplant.
- Unregulated in the West
Imported product has no quality assurance.
A comparison is not a recommendation. Neither column is being suggested for you. Which — if either — is appropriate depends on your diagnosis, history and medications, and that is a conversation for a qualified clinician.