$ cat tb-500/dosage.md
TB-500 Dosage, as the Research Reports It
What was administered, to which species, by which route — and a flat statement that no validated human protocol for the fragment exists.
Doses used in TB-500 and thymosin beta-4 research
TB-500 dosage, in the published record, means doses administered to animals — almost always of full-length thymosin beta-4 — not a human regimen. The ranges are wide and study-specific. Rodent cardiac and neurological models have used roughly 6-12 mg/kg; the embolic-stroke dose-response study gave 2, 12 and 18 mg/kg intraperitoneally, modeling an optimal dose near 3.75 mg/kg [4]. The six-month mdx muscular-dystrophy study used 150 µg twice weekly, intraperitoneally. In vitro, the protein is active at picogram-to-nanomolar amounts — as little as 10 pg stimulated keratinocyte migration [3], and nanomolar concentrations activated hair-follicle stem cells [9].
Notice the span those numbers cover. A keratinocyte assay responds to 10 picograms; a stroke model uses milligrams per kilogram of body weight — a difference of many orders of magnitude, set by the model, the route and the outcome being measured, not by any unit that converts to a person. There is no published human dose for the TB-500 fragment to anchor the range, because there is no completed controlled human trial of the fragment [12]. Every figure here is what was given to a named species in a specific study.
The single most important point: these are administered research doses, reported as data. They are not a recommendation, a conversion to a human dose, or guidance to administer anything. "Loading then maintenance" protocols that circulate in athletic and peptide-research communities are not derived from controlled human trials and have no published clinical validation — and the stroke dose-response result argues directly against the "loading" logic, since 18 mg/kg performed no better than 2 mg/kg and worse than the modeled optimum [4]. Higher was not better.
What is the half-life of TB-500?
No validated human pharmacokinetic half-life exists for the TB-500 heptapeptide. The closest human data come from the intravenous full-length Tβ4 Phase 1 study, where pharmacokinetics were dose-proportional and the half-life increased with dose across the 42-1260 mg cohorts [6] — but that characterizes the ~4963 Da protein given intravenously, not the ~889 Da fragment by the routes research-peptide users discuss.
The distinction matters for pharmacokinetics specifically. A 43-residue protein and a 7-residue peptide are cleared and degraded differently, so the parent protein's IV half-life is not a usable proxy for the fragment. Anti-doping LC-MS work has characterized TB-500 and its metabolites in equine plasma and urine — but that work exists to detect the peptide and its breakdown products for doping control, not to establish a human pharmacokinetic profile. The honest readout, the one carried on the home page, is NONE: no validated human PK for the fragment.
Routes and stability in the research
Intraperitoneal injection predominates in the rodent efficacy studies — it is the route behind the stroke dose-response work [4] and the wound-healing study [3]. Intravenous dosing was used in the human Phase 1 of full-length Tβ4 [6] and in some cardiac models. Topical and ophthalmic routes appear in the corneal and dermal wound and dry-eye work on full-length Tβ4 / RGN-259 [11]. Subcutaneous and intramuscular routes appear in community research use, but not in controlled human efficacy trials — so they carry no published efficacy or safety data for the fragment.
Route is not incidental, either: FDA's own stated rationale for the Category 2 placement cites potential immunogenicity for certain routes of administration [16], which is part of why the route a study used is logged alongside its dose throughout this site.
As a short acetylated peptide, TB-500 is supplied lyophilized — freeze-dried — and is more chemically robust than the full-length protein, but it remains subject to proteolysis and freeze-thaw degradation. Reconstitution in sterile or bacteriostatic water and cold storage are standard handling for research material. The recurring complication is supply-side: the identity, purity and correct sequence of unregulated research-grade peptide are not guaranteed, which is its own reason the dose on a label may not be the dose in the vial [12].