{"id":"tb-500","name":"TB-500","aliases":["thymosin beta-4 fragment","TB4","Tβ4"],"url":"https://lyoresearch.com/compounds/tb-500","class":{"id":"healing-peptides","name":"Tissue-repair peptides","url":"https://lyoresearch.com/classes/healing-peptides"},"summary":"TB-500 is a synthetic fragment of thymosin beta-4, a protein involved in cell migration and wound repair. Full-length thymosin beta-4 has been through phase 3 trials — as an eye drop for dry eye disease, with mixed results and no approval. The injected use people buy it for, for tendon and muscle injury, has never been tested in a completed human trial. It is banned in sport and not approved anywhere.","overall_grade":"D","overall_grade_meaning":"no human evidence","human_trials":"0 for injected use","regulatory_status":"Not approved","molecule":{"formula":"C212H350N56O78S","molecular_weight":"4963","cas":"77591-33-4","pubchem_cid":16132341,"note":"PubChem record is full-length thymosin β4 (timbetasin); TB-500 as sold is a fragment of it"},"pharmacokinetics":{"basis":"human","route":"Intravenous in the only human study (full-length thymosin β4, healthy volunteers)","half_life":"Measured but not reported as a figure; the abstract says half-life increased with dose","licensed_regimen":null,"product":null,"source":{"title":"Ruff D, et al. A randomized, placebo-controlled, single and multiple dose study of intravenous thymosin beta4 in healthy volunteers. Ann N Y Acad Sci 2010","url":"https://pubmed.ncbi.nlm.nih.gov/20536472/"}},"outcomes":[{"outcome":"Tendon, muscle & ligament healing (injected)","grade":"D","grade_meaning":"no human evidence","effect_size":"not measurable","adverse":false,"human_studies":"0 completed","evidence":"No completed phase 2 or 3 randomised trial has tested systemic thymosin beta-4 or TB-500 for tendinopathy, muscle strain or ligament injury. Animal models in rodents and rabbits only.","references":[{"citation":"Review of thymosin beta-4 / TB-500 clinical evidence: no completed systemic musculoskeletal RCT.","where":"Evidence review, 2026","url":"https://trimrx.com/blog/tb-500-research-review/"}]},{"outcome":"Dry eye disease (topical, RGN-259)","grade":"B","grade_meaning":"probable, not settled","effect_size":"small","adverse":false,"human_studies":"2 phase 3 RCTs","evidence":"ARISE-1 and ARISE-2 tested a pharmaceutical eye drop. Improvements on some ocular-surface measures; primary endpoints not consistently met, and no approval followed.","references":[{"citation":"RegeneRx. RGN-259 (thymosin beta-4 ophthalmic) ARISE-1 and ARISE-2 phase 3 trials in dry eye disease.","where":"Phase 3 programme; mixed endpoint results, no approval","url":"https://pubmed.ncbi.nlm.nih.gov/?term=RGN-259+thymosin+beta+4+dry+eye+ARISE"}]},{"outcome":"Cardiac repair","grade":"D","grade_meaning":"no human evidence","effect_size":"not measurable","adverse":false,"human_studies":"None","evidence":"Mouse and pig infarct models only.","references":[]},{"outcome":"Safety in humans (injected)","grade":"D","grade_meaning":"no human evidence","effect_size":"not measurable","adverse":true,"human_studies":"None systematic","evidence":"No systemic safety data. Independent testing of vendor products finds wide variation between labelled and actual content.","references":[]}],"regions":[{"region":"European Union","status":"Unauthorised medicinal product","note":"No marketing authorisation in any member state. Supplying it for human use is an offence under national medicines law; 'research use only' labels do not change that."},{"region":"United States","status":"Not approved; compounding under review","note":"Removed from FDA's Category 2 list on 22 April 2026; the Pharmacy Compounding Advisory Committee recommended it for the 503A bulks list in July 2026 (8–6, 1 abstention). Not on the list yet and not an approved drug. Sold otherwise as an unapproved 'research chemical'."},{"region":"United Kingdom","status":"Unlicensed medicine","note":"Not licensed by the MHRA. Selling or supplying it is an offence under the Human Medicines Regulations 2012; importing a small quantity purely for personal use is not itself an offence, but consignments are seized."},{"region":"Australia","status":"Schedule 4, unapproved","note":"Prescription-only substance not on the ARTG. Obtainable only on prescription (compounded or imported under the Personal Importation Scheme with a prescription). Named in the TGA's April 2026 advisory. Named in NSW law as a prescribed restricted substance."},{"region":"Canada","status":"Not authorised","note":"No Drug Identification Number; selling it is illegal. Among the products Health Canada seized from a domestic vendor in August 2025. Residents cannot import prescription drugs by mail."},{"region":"Sport (WADA)","status":"Prohibited at all times","note":"S2.3: 'thymosin-β4 and its derivatives, e.g. TB-500'."}],"faq":[{"q":"Does TB-500 heal injuries?","a":"Unknown in humans. The healing evidence is from rodent and rabbit models. No completed randomised trial has tested it for a human tendon, muscle or ligament injury."},{"q":"Is TB-500 the same as thymosin beta-4?","a":"No. TB-500 is a shorter synthetic fragment. The phase 3 trials used full-length pharmaceutical-grade thymosin beta-4, and they were eye drops."},{"q":"Is TB-500 banned in sport?","a":"Yes, since 1 January 2012, under WADA class S2 — prohibited at all times, in and out of competition."}],"references":[{"cite":"Review of thymosin beta-4 / TB-500 clinical evidence: no completed systemic musculoskeletal RCT.","where":"Evidence review, 2026","url":"https://trimrx.com/blog/tb-500-research-review/","note":"Secondary source; used for the absence-of-trials claim, which matches registry searches."},{"cite":"RegeneRx. RGN-259 (thymosin beta-4 ophthalmic) ARISE-1 and ARISE-2 phase 3 trials in dry eye disease.","where":"Phase 3 programme; mixed endpoint results, no approval","url":"https://pubmed.ncbi.nlm.nih.gov/?term=RGN-259+thymosin+beta+4+dry+eye+ARISE","note":"The only phase 3 human data for the parent molecule."}],"last_reviewed":"2026-09-02","literature_searched_to":"2026-09-02","changelog":[{"date":"2026-09-02","note":"Initial publication. Injected use graded D; ophthalmic programme graded separately at B."}],"license":"CC BY 4.0 — cite as “LYO Research” with a link.","methodology":"https://lyoresearch.com/methodology"}