# TB-500 Dosage in the Research Literature: Species, Routes, mg/kg

> TB-500 dosage as it appears in research: the mg/kg ranges and routes used in animal Tβ4 studies and the 42-1260 mg human Phase 1 ladder — not human protocols, with no validated fragment half-life.

The doses below are what researchers administered to animals and, for the parent protein, to Phase 1 volunteers — read as study parameters, never as human guidance.

## TB-500 Dosage in the Research Literature

TB-500 dosage figures in the published record are study parameters, not protocols — and most belong to full-length thymosin beta-4, not the 7-mer. Animal studies dose Tβ4 across a wide range: roughly 6–12 mg/kg in cardiac and neurological rodent models, and 2, 12 and 18 mg/kg intraperitoneally in the rat embolic-stroke dose-response study, where the modeled optimum landed near 3.75 mg/kg [8]. The mdx muscular-dystrophy study used 150 µg twice weekly intraperitoneally for six months.

Picogram-to-nanogram amounts are bioactive in vitro — about 10 pg was active in keratinocyte migration assays, and nanomolar Tβ4 stimulated hair-follicle stem cells [7][5]. These are mechanistic potencies, not dosing instructions.

The most important dosing lesson is the non-monotonic curve: in the stroke study, 2 and 12 mg/kg improved outcomes but 18 mg/kg did not [8]. Higher was not better, which directly undercuts community "loading" rationales.

## Human dosing on record: the Phase 1 ladder

The only human dosing data are for synthetic full-length Tβ4. A randomized, placebo-controlled Phase 1 study administered it intravenously at 42, 140, 420 and 1260 mg — a single dose, then daily for 14 days — to 40 healthy volunteers across four cohorts of ten [10]. It was well tolerated to the top dose, with no dose-limiting toxicities and dose-proportional pharmacokinetics in which half-life increased with dose [10].

This is a labeled study ladder for the parent protein, reported here as what the trial administered. It is not a human protocol for the TB-500 fragment, for which no completed human trial exists [10]. Non-clinical "loading then maintenance" schedules circulated in athletic and peptide-research communities are not derived from controlled human trials and have no published clinical validation.

## Routes studied

The routes in the literature are specific to the molecules and models tested. Intraperitoneal injection predominates in rodent efficacy studies [8]. Intravenous administration was used in the human Phase 1 of full-length Tβ4 and in some cardiac models [10]. Topical and ophthalmic routes appear in corneal and dermal wound work and the dry-eye trials of full-length Tβ4 / RGN-259 [7][10]. Subcutaneous and intramuscular routes appear in community research use but not in controlled human efficacy trials.

As a short acetylated peptide, TB-500 is supplied lyophilized for research use and reconstituted in bacteriostatic or sterile water with refrigeration. It is more chemically robust than the full-length protein but still subject to proteolysis and freeze-thaw degradation. Identity and purity of research-grade material — including whether a vial contains the fragment or the full-length protein — is a recurring concern.

## TB-500 Half-Life: What Is and Is Not Known

No validated human pharmacokinetic half-life exists for the TB-500 heptapeptide [10]. That is a flagged gap, not an oversight: the only human PK on record is for full-length Tβ4, where the Phase 1 study reported dose-proportional kinetics with half-life increasing as dose increased [10]. Anti-doping LC-MS work has characterized TB-500 and its metabolites in equine plasma and urine — but for detection, not for human pharmacokinetic modeling [1]. Any single TB-500 half-life figure presented as a human number is unsupported by the literature.

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TB-500 Source reconciles the Ac-LKKTETQ record line by line — each figure matched to its study, the seven-residue fragment held on a separate line from the full-length thymosin beta-4 its data borrow from, and the human-evidence line left openly unbalanced; a register of the facts, not a clinic, a pharmacy, or a prescription.