TB-500 Dosage as It Appears in the Research Record

Doses Used in the Research Literature

TB-500 dosage is best described as a research-context range, not a recommendation, and almost every published dose is a full-length thymosin beta-4 dose in animals. Rodent efficacy studies dose the protein across a wide band: roughly 6-12 mg/kg in cardiac and neurological models, and 2-18 mg/kg intraperitoneally in the embolic-stroke dose-response study, where the modeled optimum sat near 3.75 mg/kg ^[4]. A muscular-dystrophy study used 150 micrograms twice weekly intraperitoneally for six months.

The one human dosing dataset is intravenous and belongs to the protein: synthetic thymosin beta-4 was given at 42, 140, 420, and 1260 mg — single dose, then daily for 14 days — in the Phase 1 safety study ^[6]. Picogram-to-nanogram amounts are bioactive in vitro; as little as 10 picograms stimulated keratinocyte migration ^[3], and nanomolar thymosin beta-4 activated hair-follicle stem cells ^[7].

None of this is a human protocol for the fragment. The non-clinical "loading then maintenance" schedules that circulate in athletic and peptide-research communities are not derived from controlled human trials and have no published clinical validation. The non-monotonic stroke result — where 18 mg/kg gave no benefit while 2 and 12 mg/kg did — is a direct caution against assuming more is better ^[4].

Why the dose numbers don't transfer to the fragment

The doses above describe a 4963 Da protein, and TB-500 is an 889 Da fragment of it — roughly a fifth of the mass ^[5]. A milligram of full-length thymosin beta-4 and a milligram of Ac-LKKTETQ are therefore not the same number of molecules, and the two are not pharmacologically interchangeable at equal mass. That alone makes it unsound to read a thymosin beta-4 study's milligram figure across to a fragment regimen, even before the deeper question of whether the fragment reproduces the protein's activity at all ^[5].

There is also no validated way to convert in vitro potency into an in vivo dose here. The picogram-scale activity in keratinocyte assays ^[3] and the nanomolar activity in hair-follicle assays ^[7] are concentrations at a cell, not systemic doses in an animal, and they were measured for the parent protein. They establish that the molecule is bioactive at low concentrations in a dish; they do not establish a dose for anything.

The practical conclusion is the cautious one. The published, characterized dosing record for this compound is animal and full-length-protein dosing, the single human dosing dataset is the intravenous Phase 1 of the protein ^[6], and no controlled human dosing study of the Ac-LKKTETQ fragment exists for any indication ^[5]. Everything beyond that is extrapolation.

Routes studied

Intraperitoneal injection predominates in the rodent efficacy literature, including the embolic-stroke dose-response work ^[4]. Intravenous administration was used in the human Phase 1 study of full-length thymosin beta-4 and in some cardiac models ^[6]. Topical and ophthalmic routes appear in corneal and dermal wound work and in dry-eye trials of the protein formulation (RGN-259) ^[12]. Subcutaneous and intramuscular routes are community research-use routes; they are not drawn from controlled human efficacy trials.

The compound 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, and identity and purity of research-grade material are a recurring concern — peptide identity, purity, and correct sequence (full-length versus fragment) are not guaranteed in unregulated supply, which complicates the interpretation of any result obtained with such material.