# TB-500 Dosage in the Research Literature and Pharmacokinetics | TB-500

> TB-500 dosage as the research record describes it: animal mg/kg ranges for thymosin beta-4, the human Phase 1 IV doses (42–1260 mg), and why no validated human half-life exists for the seven-mer.

This page reports what was administered, to which species, by which route — not what anyone should take. The fragment has no validated human pharmacokinetics of its own.

## TB-500 Dosage in the Research Literature

TB-500 dosage in the published record is animal-model dosing of full-length thymosin beta-4, plus a single human Phase 1 study of the parent protein. None of it is human guidance for the fragment, and this page describes it as a research record rather than a protocol.

Animal studies dose Tβ4 across a wide range. Cardiac and neurological rodent models have used roughly 6–12 mg/kg; the embolic-stroke dose-response study used 2, 12, and 18 mg/kg intraperitoneally, with a modeled optimal near 3.75 mg/kg [13]. A six-month muscular-dystrophy study in mdx mice used 150 µg twice weekly intraperitoneally [4]. At the other end of the scale, picogram-to-nanogram amounts are bioactive in vitro — about 10 pg was active in keratinocyte migration assays [3].

In humans, the Phase 1 study dosed synthetic Tβ4 intravenously at 42, 140, 420, and 1260 mg — a single dose, then daily for 14 days — and reported it well tolerated with dose-proportional pharmacokinetics [6]. That is the only controlled human dosing in the literature, and it used the full protein.

The routes studied include intraperitoneal (the predominant rodent efficacy route), intravenous (the human Phase 1 and some cardiac models), and topical or ophthalmic delivery (corneal and dermal wound and dry-eye work with full-length Tβ4 / RGN-259) [3]. The "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.

## Half-Life and Pharmacokinetics

No validated human pharmacokinetic half-life exists for the TB-500 heptapeptide. That is the precise, correct statement, and it is worth stating plainly rather than padding with estimates.

What the record does contain is the parent protein's PK from the Phase 1 IV study, where half-life increased with dose — pharmacokinetics were dose-proportional across the 42–1260 mg range [6]. Separately, anti-doping LC-MS work characterizes TB-500 and its metabolites in equine plasma and urine, but that work is built for detection, not for human pharmacokinetics — it tells you the fragment can be measured in a doping sample, not how it behaves clinically.

For stability, 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 is still subject to proteolysis and freeze-thaw degradation, and the identity and purity of research-grade material are a recurring concern.

## Non-monotonic dosing: more is not the goal

One result from the stroke literature deserves its own note because it cuts against the community "loading" logic directly. In the rat embolic-stroke dose-response study, 2 and 12 mg/kg improved neurological outcomes but 18 mg/kg did not [13]. The relationship was non-monotonic — a higher dose was not a better dose, and the modeled optimum sat in the middle of the tested range near 3.75 mg/kg.

That single dataset undermines any framing in which escalating amounts straightforwardly escalate benefit. It is an animal result, and it is not a recommendation in either direction; it is reported here because it is one of the cleaner dose-response findings in the record and it contradicts a common assumption rather than confirming one.

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A risograph reading of the TB-500 record, where the Ac-LKKTETQ fragment overlaps its parent protein thymosin beta-4 the way two inks overlap on the page — each finding plated to its study, the human-evidence panel left blank, and the FDA 503A standing printed first; no clinic behind the press and nothing here dispensed or sold.