A Research Codex ~ Chapter V
TB-500 in the Dosing Literature: What Was Administered, and to Whom
The doses, routes, and pharmacokinetics recorded in the research — set out as study findings, with no human protocol stated or implied.
How to read TB-500 in the dosing literature
What follows describes TB-500 in the dosing literature as a record of what researchers administered, to which species, by which route. It is not a dosing recommendation, and nothing here is a human protocol. The framing is deliberate: this codex reports "X mg/kg in [species]" and never "take X." The substance is not an approved medicine and has no completed controlled human trial of its own, so a validated human dose does not exist to report [6].
Animal studies dosed full-length thymosin beta-4 across a wide range: roughly 6 to 12 mg/kg in cardiac and neurological rodent models; 2 to 18 mg/kg intraperitoneally in the embolic-stroke dose-response study, with a modeled optimal near 3.75 mg/kg [4]; and 150 micrograms twice weekly by intraperitoneal injection for six months in a muscular-dystrophy study [10]. The single human dosing program — the Phase 1 study — gave intravenous thymosin beta-4 at 42, 140, 420, and 1260 mg [6]. Picogram-to-nanogram amounts are bioactive in vitro, with about 10 picograms active in keratinocyte migration assays [3].
Routes studied in the literature
The route depends on the model. Intraperitoneal injection predominates in rodent efficacy studies [4]. Intravenous administration was used in the human Phase 1 study of full-length thymosin beta-4 and in some cardiac models [6]. Topical and ophthalmic routes carry the corneal and dermal wound work, including the RGN-259 ophthalmic program [8], and an inhaled route was used in the 2024 pulmonary-fibrosis study [12]. Subcutaneous and intramuscular routes circulate in community research use, but they are not drawn from controlled human efficacy trials and carry no validated human protocol.
TB-500 Half-Life in the Research Record
No validated human pharmacokinetic half-life exists for the TB-500 heptapeptide. The relevant human pharmacokinetic data are for full-length thymosin beta-4: in the intravenous Phase 1 study the half-life increased with dose, consistent with dose-proportional pharmacokinetics, rather than resolving to a single fixed figure [6]. Anti-doping LC-MS work characterizes TB-500 and its metabolites in equine plasma and urine for detection purposes, not to establish a human half-life [9]. A precise TB-500 half-life for the fragment in humans is therefore not something the literature supports stating.
How Long Does TB-500 Stay in Your System?
There is no validated human clearance window for the TB-500 fragment, so the honest answer is that the literature does not fix one [6]. What the literature does support is detectability: anti-doping science developed LC-MS assays that identify TB-500 and its metabolites in equine and human matrices, with reported limits of detection in the range of 0.01 to 0.02 ng/mL in horses [9]. Detection science answers "can it be found," not "how long until cleared" in a human dosing sense, and the two questions should not be conflated. The reconstitution and stability details — lyophilized powder kept refrigerated after reconstitution in sterile or bacteriostatic water — are storage facts, not pharmacokinetics.
On community loading protocols
Non-clinical "loading then maintenance" schedules that circulate in athletic and peptide-research communities are not derived from controlled human trials and have no published clinical validation. The stroke dose-response is the cleanest argument against them: benefit appeared at 2 and 12 mg/kg but not at 18 mg/kg, a non-monotonic curve in which higher was not better [4]. This codex records what was studied; it does not translate animal milligram-per-kilogram doses into human use, and it presents no protocol.