# TB-500 Dosage in the Research Literature — Routes, Half-Life and PK | TB-500

> TB-500 dosage in the research literature: the milligram-per-kilogram ranges used in animal studies of thymosin beta-4, the human Phase 1 intravenous doses, routes studied, and why no validated human half-life exists for the fragment.

What was administered, to which species, by which route — never a human recommendation. Most dose figures are for full-length thymosin beta-4.

## TB-500 Dosage in the Research Literature

TB-500 dosage figures in the literature are research-context figures, not protocols. They describe what was administered to animals or to volunteers in a controlled study, and almost all of them are for full-length thymosin beta-4, not the heptapeptide. Animal studies dosed the protein across a wide range: roughly 6–12 mg/kg in cardiac and neurological rodent models; 2, 12, or 18 mg/kg intraperitoneally in the embolic-stroke dose-response study, where the optimal dose was modeled near 3.75 mg/kg [4]; and 150 µg twice weekly intraperitoneally for 6 months in the mdx muscular-dystrophy study [9].

Picogram-to-nanogram amounts are bioactive in vitro — about 10 pg was active in keratinocyte migration assays, and nanomolar thymosin beta-4 stimulates hair-follicle stem cells [3]. The non-clinical "loading then maintenance" protocols circulated in athletic and peptide-research communities are not derived from controlled human trials and have no published clinical validation [13]. The stroke dose-response is the clearest reason for caution: 18 mg/kg performed no better than 2 mg/kg, so escalating the dose is not supported by the data [4].

### How much TB-500 should be taken per week during a loading phase?

Community "loading then maintenance" protocols are not derived from controlled human trials and have no published clinical validation [13]. Animal studies dosed full-length thymosin beta-4 by body weight in milligram-per-kilogram ranges [4], which cannot be translated into a human weekly amount.

## TB-500 Half-Life and Pharmacokinetics

No validated human pharmacokinetic half-life exists for the TB-500 heptapeptide [13]. The closest human data come from the full-length protein: in a randomized, placebo-controlled Phase 1 study, intravenous synthetic thymosin beta-4 in 40 healthy volunteers showed dose-proportional pharmacokinetics, with half-life increasing as dose increased [6]. Anti-doping LC-MS work has characterized TB-500 and its metabolites in equine plasma and urine, but that work is built for detection, not for human pharmacokinetic modeling [13]. For the broader [human clinical status of thymosin β4](/research), the only completed human data are for the full-length protein.

### What is the half-life of TB-500 and how often should it be dosed?

No validated human pharmacokinetic half-life exists for the TB-500 heptapeptide [13]. In the intravenous full-length thymosin beta-4 Phase 1 study, half-life increased with dose, i.e. the pharmacokinetics were dose-proportional [6]. There is no evidentiary basis for a fragment dosing frequency in humans.

## Routes studied and material handling

Routes in the efficacy literature are dominated by what the researchers used, not by what circulates in communities. Intraperitoneal dosing predominated in rodent efficacy studies [4]. Intravenous dosing appeared in the human Phase 1 of full-length thymosin beta-4 and in some cardiac models [6]. Topical and ophthalmic routes were used in corneal and dermal wound work and in dry-eye trials of the clinical-grade formulation RGN-259 [3]. Subcutaneous and intramuscular routes are community research-use routes that are not drawn from controlled human efficacy trials [13].

### How does subcutaneous vs intramuscular injection of TB-500 compare?

Rodent efficacy studies predominantly used intraperitoneal dosing [4]; subcutaneous and intramuscular are community research-use routes not validated in controlled human efficacy trials [13]. No comparative human data establish a difference between them for the fragment.

TB-500 is supplied as a lyophilized powder, 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, and the identity and purity of research-grade material are a recurring concern [13].

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A bento board of the TB-500 record — each finding tiled and cited, every full-length-versus-fragment caveat flagged in the corner, with no clinic behind the board and nothing here dispensed or sold.