TB-500 Dosing Quantities in the Research Literature

TB-500 Dosing Quantities in the Research Literature

TB-500 dosage in the literature is reported as quantities administered to named species, not as human protocols. Animal studies dosed full-length thymosin beta-4 across a wide range: roughly 6-12 mg/kg in cardiac and neurological rodent models, 2-18 mg/kg intraperitoneal in the embolic-stroke dose-response study (with a modeled optimum near 3.75 mg/kg) ^[4], and 150 µg twice weekly intraperitoneally for six months in the mdx muscular-dystrophy study. Picogram-to-nanogram amounts are bioactive in vitro — about 10 pg was active in keratinocyte-migration assays, and nanomolar thymosin beta-4 stimulates hair-follicle stem cells ^[3].

The only human dosing on record is for full-length thymosin beta-4, not the fragment. In a randomized, placebo-controlled Phase 1 study, synthetic thymosin beta-4 was given intravenously to 40 healthy volunteers at 42, 140, 420 or 1260 mg — a single dose, then daily for 14 days — and was well tolerated to 1260 mg with no dose-limiting toxicities and dose-proportional pharmacokinetics ^[6].

This site does not convert any of these into a human dose. The studied quantities are reported as what was administered in each model; the non-monotonic stroke result is a direct reason quantity does not scale linearly to effect ^[4]. Non-clinical "loading then maintenance" protocols circulated in athletic and peptide-research communities are not derived from controlled human trials and have no published clinical validation.

TB-500 Half-Life and Clearance in the Research Record

No validated human pharmacokinetic half-life exists for the TB-500 heptapeptide. The only human PK on record is for full-length thymosin beta-4, where the Phase 1 intravenous study found dose-proportional pharmacokinetics with half-life increasing as dose increased ^[6]. The fragment's own clearance has not been characterized in a controlled human study.

What the analytical literature does provide is detection-grade clearance data, not therapeutic PK. Anti-doping LC-MS work characterizes TB-500 and its metabolites in equine plasma and urine, and later UHPLC-Orbitrap MS/MS work quantified the parent peptide and its metabolites in vitro and in rats ^[7][14]. These methods exist to detect the compound after administration, not to model a human dosing interval. Anyone asking how long TB-500 stays in the body is best served by that detection science — covered in full on the detection page — and by the candid fact that the human PK question is unanswered for the fragment. See TB-500 half-life and clearance.

Routes studied and material stability

The routes that appear in the literature are intraperitoneal (predominant in rodent efficacy studies), intravenous (the human Phase 1 of full-length thymosin beta-4 and some cardiac models), and topical or ophthalmic (corneal and dermal wound and dry-eye work with full-length thymosin beta-4, including the RGN-259 formulation) ^[3][6]. Subcutaneous and intramuscular routes appear in community research use but not in controlled human efficacy trials.

The route matters more than community discussion usually allows. FDA's own safety rationale for placing the LKKTETQ fragment in 503A Category 2 cited potential immunogenicity specifically for certain routes of administration — a route-dependent concern, not a blanket one ^[17]. The Phase 1 human safety data are intravenous and for the full-length protein; they do not transfer to a subcutaneous fragment dosed outside a trial ^[6].

As a material, TB-500 is supplied as a lyophilized powder for research use, reconstituted in bacteriostatic or sterile water and kept refrigerated. As a short acetylated peptide it is more chemically robust than the full-length protein, but it remains subject to proteolysis and freeze-thaw degradation. Identity and purity of research-grade material is a recurring concern: peptide identity, purity, and correct sequence — full-length protein versus seven-mer fragment — are not guaranteed in unregulated supply, which also complicates interpreting anecdotal results ^[7].