Dosing in the literature
TB-500 dosage in animal studies, half-life, and what is genuinely unknown
The published doses are animal figures for the full-length protein. There is no validated human pharmacokinetic profile for the TB-500 fragment — this page states that plainly rather than filling the gap with community numbers.
What the published TB-500 dosage figures actually are
Every published TB-500 dosage figure worth citing is an animal dose of full-length thymosin beta-4, or a human dose of the parent protein in a single Phase 1 study — not a validated dosing schedule for the fragment, and never a human-use recommendation. This page reports what was administered, to which species, by which route, and at which dose, in the language of the studies. It does not translate any of it into a protocol.
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 intraperitoneally in the embolic-stroke dose-response study, with a modeled optimal dose near 3.75 mg/kg [7]; and 150 micrograms twice weekly intraperitoneally for six months in the mdx muscular-dystrophy study [8]. Picogram-to-nanogram amounts are bioactive in vitro — about 10 picograms was active in keratinocyte migration assays [2]. The human Phase 1 study dosed synthetic thymosin beta-4 intravenously at 42, 140, 420, and 1260 mg, as a single dose and then daily for 14 days [4].
What is the half-life of TB-500?
No validated human pharmacokinetic half-life exists for the TB-500 heptapeptide — that is the precise and honest answer. In the intravenous full-length thymosin beta-4 Phase 1 study, pharmacokinetics were dose-proportional and half-life increased with dose [4]. Anti-doping LC-MS work has characterized TB-500 and its metabolites in equine plasma and urine, but that work is built for detection, not for establishing a human PK profile [4]. So the parent protein has partial human PK data; the fragment, by name, does not.
As a short acetylated peptide, TB-500 is more chemically robust than the full-length protein, but it remains subject to proteolysis and to degradation across freeze-thaw cycles. Material is supplied lyophilized and reconstituted in bacteriostatic or sterile water and kept refrigerated. None of that yields a validated half-life for the seven-mer.
How long does TB-500 stay in your system?
There is no validated human pharmacokinetic profile for the TB-500 fragment, so a precise human clearance window cannot be stated [4]. What does exist is anti-doping science: LC-MS assays have been developed to detect TB-500 and its metabolites in biological matrices, originally in equine plasma and urine, because the compound was encountered as a designer drug in racehorses [4]. Those methods define detection windows for testing purposes, not a clinical clearance figure. In the human Phase 1 study of the full-length parent protein, half-life increased with dose, indicating dose-dependent clearance for that molecule [4] — but that is the protein, not the heptapeptide.
How much TB-500 should be taken per week during a loading phase?
Community "loading then maintenance" protocols have no basis in controlled human trials and are not validated dosing [4]. The published doses are animal figures for full-length thymosin beta-4 — for example, 150 micrograms twice weekly intraperitoneally in mdx mice [8], and 2–18 mg/kg intraperitoneally in stroke models [7]. The non-monotonic stroke result, where 18 mg/kg gave no benefit, specifically undercuts a "more is better" loading rationale [7].
How does subcutaneous vs intramuscular injection of TB-500 compare?
Rodent efficacy studies predominantly used intraperitoneal dosing [7][8]; subcutaneous and intramuscular administration are community research-use routes, not routes derived from controlled human efficacy trials. The human Phase 1 study used the intravenous route for the full-length protein [4]. No comparative human pharmacokinetic data exist across these routes for the TB-500 fragment.
What is the half-life of TB-500 and how often should it be dosed?
No validated human pharmacokinetic half-life exists for the TB-500 heptapeptide [4]. In the intravenous full-length thymosin beta-4 Phase 1 study, half-life increased with dose [4]. Community dosing frequencies are not clinically validated, and the non-monotonic animal dose-response argues against assuming higher or more frequent is better [7].