# TB-500 Dosage in the Research Literature: Routes, Half-Life, and Doses by Species

> TB-500 dosage as the research literature reports it — studied at 2 to 18 mg/kg in rodents, 42 to 1260 mg intravenously in a human Phase 1 of full-length thymosin beta-4. Routes, the non-monotonic stroke data, and the absence of validated human PK. Cited, never prescribed.

Doses framed as studied in a species and route — never as instructions — with the non-monotonic stroke data and the missing human PK flagged.

## TB-500 dosage in the research literature

TB-500 dosage in the research literature is reported as a dose given to a species by a route, not as a human protocol — and almost every dose on record belongs to full-length thymosin β4, not the Ac-LKKTETQ fragment. Animal studies span a wide range: roughly 6–12 mg/kg in some cardiac and neurological rodent models, and 2, 12, and 18 mg/kg intraperitoneally in the embolic-stroke dose-response study, where a modeled optimal dose of about 3.75 mg/kg was proposed [4]. The chronic muscular-dystrophy study used 150 µg twice weekly intraperitoneally for six months [9].

Human dosing exists only for the full-length protein: the Phase 1 study gave synthetic Tβ4 intravenously at 42, 140, 420, and 1260 mg — a single dose, then daily for 14 days — and reported it well tolerated with no dose-limiting toxicities [6]. Picogram-to-nanomolar amounts are bioactive in vitro, with about 10 pg active in keratinocyte migration assays [3]. None of these figures is a human-use recommendation for the fragment, and this site offers none.

## The non-monotonic dose response

Higher is not necessarily better, and the stroke data show it directly. In the rat embolic-stroke study, 2 and 12 mg/kg improved neurological outcome significantly from day 14 through day 56, but 18 mg/kg produced no significant benefit [4]. A modeled optimum near 3.75 mg/kg sat well below the top dose tested. This non-monotonic shape is the single most important dosing fact on the board, because it directly undercuts the community "loading" rationale: escalating the dose did not escalate the effect, and at the high end the effect disappeared.

## TB-500 half-life: what the pharmacokinetics show

There is no validated human pharmacokinetic half-life for the TB-500 heptapeptide. In the intravenous full-length Tβ4 Phase 1 study, half-life increased with dose — pharmacokinetics were dose-proportional [6]. Anti-doping LC-MS work characterizes TB-500 and its metabolites in equine plasma and urine for detection purposes, not for human pharmacokinetics. Any specific half-life figure quoted for the fragment in humans is not supported by a controlled study.

## Routes studied

The intraperitoneal route dominates the rodent efficacy literature [3][4][9]. Intravenous administration was used in the human Phase 1 of full-length Tβ4 and in some cardiac models [6][2]. Topical and ophthalmic routes were used in corneal and dermal wound work and in dry-eye trials of clinical-grade Tβ4 [3][11]. Subcutaneous and intramuscular routes circulate in community research use but do not derive from controlled human efficacy trials. As with every figure on this page, the route belongs to a specific study and a specific molecule — most often the full-length protein.

## Why community loading protocols are not validated dosing

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. Two facts on this board explain why they should not be read as dosing guidance: the dose response is non-monotonic, so more is not reliably better [4], and there is no validated human PK for the fragment to anchor an interval [6]. Add the identity and purity uncertainty of unregulated material, and a community protocol describes a practice, not an evidence-based dose. This site reports the research doses on record and stops there.

## Stability and handling, as reported

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 it remains subject to proteolysis and freeze-thaw degradation. These are handling notes drawn from research-use practice, not directions for human administration, and they do not address the central uncertainty — whether a given vial contains the correct fragment at the stated purity.

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A cool-green research board for the TB-500 record — the Ac-LKKTETQ fragment routed as its own net apart from the full-length thymosin beta-4 it is sold as, the empty human-trial pad left open, the tumor-angiogenesis trace flagged and the FDA 503A standing read first; no clinic solders this board and nothing here is dispensed or sold.