TB-500 Dosage: What Thymosin β4 Trials Used vs the Marketed Fragment

TB-500 vs Thymosin β4 — What Was Actually Dosed

Any honest reading of "TB-500 dosage" has to start with which molecule the number refers to, because the answer changes what dosing data even applies. The injectable research chemical sold as TB-500 is, on analytical characterisation, the acetylated synthetic fragment Ac-LKKTETQ — a short peptide corresponding to the central actin-binding motif of thymosin β4, not the full protein.^[1] Full-length thymosin β4 (Tβ4), by contrast, is a 43-amino-acid actin-sequestering peptide, and it is the entity used in the human clinical trials on the record.^[2]

This fragment-versus-full-peptide split is the single most important thing on this page. Short actin-binding fragments of Tβ4 do retain measurable activity in preclinical models, which is why a fragment was marketable as a research tool in the first place.^[3] But biological activity in a cell assay is not a dose. Because the marketed TB-500 fragment and full-length Tβ4 are chemically different molecules with different sizes and routes of study, the mg or µg figures reported in Tβ4 human and animal trials cannot be transferred onto a "TB-500" vial as if they were the same drug.

The practical consequence for a research reader: when a source quotes a "TB-500 dose," it is almost always either (a) borrowing a full-length Tβ4 trial number that used a different molecule and route, or (b) repeating an unsourced community protocol with no trial behind it. Neither is a validated human dose for the injectable fragment. The sections below separate what the published trials actually administered — by molecule, route, and phase — from the marketing shorthand.

Doses & Routes in Thymosin β4 Human Trials

The human clinical record belongs to full-length thymosin β4, delivered by three routes across ophthalmology, systemic infusion, and topical wound care — not to the injectable TB-500 fragment. The table records the route and phase for each programme. Exact per-dose mg/µg values were not uniformly reported across the accessible abstracts; the dose column gives the figures where a trial stated them and otherwise records the reported dosing structure ("ascending", "escalating", or a fixed concentration) rather than inventing a number.

Two things stand out. First, every one of these programmes used full-length Tβ4, and the two most detailed (IV RGN-352 and ophthalmic RGN-259) are dose-defined by route and formulation — an IV ascending-dose safety study and a fixed 0.1% eye-drop concentration carried through to a Phase 3 neurotrophic keratopathy trial^[6] — rather than by a musculoskeletal injection dose. Second, none of them evaluated the injectable Ac-LKKTETQ fragment marketed as TB-500. There is, at the time of writing, no registered human trial and no published human pharmacokinetic profile for that fragment, which is why it has no validated human dose to cite.

Animal Wound-Healing Doses

The bulk of the tissue-repair dosing data for thymosin β4 comes from rodent wound-healing models, delivered either as a topical application to the wound or by intraperitoneal (IP) injection. These are animal doses reported in the primary literature; they are recorded here as what those studies administered, and they do not translate to a human dose.

• Topical, full-thickness skin wounds (rodent). Malinda and colleagues reported that topical thymosin β4 applied per wound accelerated wound closure and re-epithelialisation in a rat full-thickness dermal model, with the dose expressed on a microgram-per-wound basis rather than a systemic mg/kg figure.^[8]
• Topical and systemic, diabetic (db/db) wounds. Philp and colleagues studied full-length Tβ4 alongside a synthetic peptide containing its actin-binding domain in db/db diabetic mice, reporting improved dermal wound repair; dosing in this work was applied at the wound level and, in the actin-binding-fragment arm, tests the same short-motif chemistry that underlies the marketed TB-500 fragment.^[9]

The qualitative pattern across these rodent studies is a reproducible wound-healing signal for Tβ4 and Tβ4 actin-binding fragments. What the animal record does not provide is a validated bridge to a human dose: published animal doses do not map cleanly onto a human exposure, and this page makes no attempt to convert them. Anyone presenting a specific human "TB-500 protocol" derived from these figures is extrapolating beyond the data.

Reconstitution & Handling (Research Use)

Because there is no validated human dose, the only "dosing" relevant to a research setting is the working concentration a laboratory sets for an in-vitro assay — a function of reconstitution volume, not of any human protocol. Standard handling for the lyophilized research fragment mirrors other short research peptides:

• Storage of the lyophilisate. 2-8°C protected from light for routine use; -20°C for long-term storage. In warm climates, documented cold-chain handling from arrival to bench-side matters — short ambient excursions during last-mile delivery are the most common stability risk.
• Reconstitution. Bacteriostatic water (0.9% benzyl alcohol as preservative) is the standard reagent. The reconstitution volume for a 10mg research vial is chosen from the downstream assay concentration the research protocol requires — it is a bench parameter, not a human dose. See the Remy bacteriostatic water guide and peptide stability and storage guide for handling depth, and the reconstitution calculator for the per-volume working concentration.
• Post-reconstitution storage. 2-8°C with use inside the research-protocol working window; reconstituted research-grade solutions are typically used within a few weeks, though stability programmes vary by laboratory.

This page provides no human-use dosing or veterinary instructions and is not a clinical-protocol document. The catalog format is documented on the TB-500 10mg research vial page, and each vial is supplied at >99% HPLC purity.

Anti-Doping Status

TB-500 is treated as a prohibited substance in sport and is detectable. Analytical chemists have published a validated liquid chromatography–mass spectrometry (LC-MS) doping-control method that identifies the TB-500 fragment (Ac-LKKTETQ) in biological samples, which is what allows anti-doping laboratories to screen for it.^[10] The same analytical work underpins the identification of the marketed compound as the acetylated Ac-LKKTETQ fragment rather than full-length Tβ4.^[1]

This is a factual statement about the substance's regulatory and analytical status, not advice. TB-500 sits in the growth-factor / peptide category that anti-doping programmes prohibit, and its detectability means presence in a sample can be established by validated method. Remy Peptides supplies TB-500 strictly for in-vitro laboratory research use only; it is not framed for human use, dosing, or veterinary use, and nothing here should be read as guidance on use in humans or animals.

For the underlying mechanism and preclinical background behind the fragment, see the TB-500 thymosin β4 research overview; for a side-by-side with the other healing-research peptide most often compared to it, see the BPC-157 vs TB-500 comparison.