Searches for a TB-500 dosage usually expect a number. The honest, evidence-based answer is that there is no established or approved human dose for TB-500, and — crucially — TB-500 itself has never been the subject of a registered human clinical trial. The human studies people often point to were conducted on the full Thymosin β4 protein formulated as specific pharmaceutical products, not on the injectable TB-500 fragment sold for research. This article documents what has actually been investigated, in what, and at what quantities — it is a review of published research, not a recommendation.
What is TB-500?
TB-500 is a synthetic peptide corresponding to a short seven-amino-acid sequence (Lys-Leu-Lys-Lys-Thr-Glu-Thr-Gln, often written LKKTETQ) taken from the actin-binding region of Thymosin β4 (Tβ4). Thymosin β4 is a naturally occurring 43-amino-acid, actin-sequestering peptide found in most human cells and studied for roles in cell migration, angiogenesis and tissue repair. Because TB-500 reproduces only a fragment of that parent molecule, the two are not interchangeable and may not share identical activity. TB-500 has not been approved by the MHRA, EMA or FDA for any use and is supplied strictly as a laboratory research reagent.
Is there an established TB-500 dosage?
No. There is no approved medical dose, and no published Phase 1–3 clinical trial has investigated the TB-500 fragment in humans at any quantity. The clinical evidence that does exist belongs to the full Thymosin β4 peptide, developed by RegeneRx Biopharmaceuticals as distinct, formulation-specific drug candidates (for example an injectable form, RGN-352, and a topical eye-drop form, RGN-259). Those are different products from injectable TB-500, so their trial parameters cannot be read as a TB-500 dose. The sections below separate that human Thymosin β4 research from preclinical animal work, and neither establishes a human TB-500 dosage.
TB-500 dosage investigated in human clinical research
To be precise: the studies below investigated Thymosin β4 (the full peptide) in defined pharmaceutical formulations — not the TB-500 fragment. They are included because they are the only human data in this space, and to show exactly why they do not answer “what is the TB-500 dose.”
| Study (product) | Participants | Quantity investigated | Frequency | Route | Duration | Outcome measure |
|---|---|---|---|---|---|---|
| RGN-352 Phase 2, acute myocardial infarction (NCT01311518) | Adults post-PCI | 450 mg or 1200 mg (two arms) vs placebo | Daily for 3 days, then weekly for 4 weeks | Intravenous | ~5 weeks | Safety & tolerability |
| RGN-259 Phase 2, severe dry-eye disease (Sosne et al., 2015) | Small patient cohort | 0.1% ophthalmic solution | Multiple times daily | Topical (eye drops) | 28 days | Signs & symptoms of dry eye |
| RGN-259 Phase 3, neurotrophic keratopathy | Randomised, placebo-controlled | 0.1% ophthalmic solution | Several times daily | Topical (eye drops) | Multi-week | Corneal healing & comfort |
In the RGN-352 cardiac study, participants were assigned to one of two intravenous Thymosin β4 amounts (450 mg or 1200 mg) or placebo to assess safety after a heart attack. In the RGN-259 ophthalmic programme, a 0.1% Thymosin β4 eye-drop solution was studied for dry-eye disease and for neurotrophic keratopathy. None of these used the injectable TB-500 fragment, and none was designed to define a general-purpose “dose” of TB-500.
Dose-escalation research
The clearest example of a designed comparison is the RGN-352 myocardial-infarction trial, which built in two fixed intravenous amounts — 450 mg and 1200 mg — alongside placebo, so investigators could compare tolerability across a lower and a higher quantity of the full Thymosin β4 peptide. This describes the study design for a specific injectable formulation; it is not a titration scheme for TB-500 and is reported here only as historical trial structure.
Preclinical (animal and laboratory) research
Most TB-500 / Thymosin β4 evidence is preclinical. Representative published quantities include:
- Rat full-thickness wound model (Malinda et al., 1999): Thymosin β4 applied topically at 5 µg per wound, or intraperitoneally at 60 µg at wounding and every other day; re-epithelialisation increased by 42% at day 4 and up to 61% at day 7 versus saline, with more contraction, collagen and angiogenesis.
- Rodent cardiac ischaemia models: intraperitoneal Thymosin β4 on the order of ~10 µg per animal per day has been used to study myocardial protection.
- Burn-injury rat model: intraperitoneal Thymosin β4 at 2, 6 and 18 µg was compared to study effects on myocardial apoptosis.
These are preclinical findings and cannot be interpreted as establishing an equivalent human dosage. Animal quantities are tied to species, body weight and route (micrograms per animal, often intraperitoneal) and cannot be converted into a human amount.
What did different dosage groups show?
Where multiple amounts were compared, the reported picture is limited. In the RGN-352 cardiac trial the 450 mg and 1200 mg intravenous arms were evaluated primarily for safety and tolerability rather than a dose–response efficacy curve. In the burn-injury animal work, the graded 2 / 6 / 18 µg design was used to look for dose-related effects on cardiac apoptosis. No published human dose–response relationship exists for the TB-500 fragment, because it has not been tested in humans.
Safety and adverse events reported in research
Human safety data relate to Thymosin β4 formulations, not TB-500. The RGN-352 study's stated purpose was to assess safety and tolerability of intravenous Thymosin β4 after myocardial infarction; the RGN-259 eye drops were reported as well tolerated in dry-eye and corneal-healing studies. These datasets are small and formulation-specific. For the injectable TB-500 fragment sold for research, there is no controlled human safety dataset at all. TB-500 is also prohibited in sport by the World Anti-Doping Agency, which is relevant context but not a safety evaluation.
What the research does not tell us
- It does not tell us a human dose of TB-500 — the fragment has never been in a registered human trial.
- It does not allow us to assume the full Thymosin β4 trial parameters (mg intravenous, or 0.1% eye drops) transfer to the injectable TB-500 fragment; they are different molecules and formulations.
- Animal micrograms-per-animal figures cannot be converted to a human amount.
- There is no long-term human safety, pharmacokinetic or efficacy data for TB-500.
TB-500 research timeline
- 1999 — Malinda et al. report accelerated wound healing with Thymosin β4 in a rat model (preclinical).
- 2010s — RegeneRx advances full Thymosin β4 as formulation-specific candidates: RGN-352 (intravenous, cardiac) and RGN-259 (topical ophthalmic), reaching Phase 2/3 in eye disease.
- Ongoing — TB-500 (the fragment) remains a research reagent with no registered human trials of its own.
Key takeaway
Published research has investigated the full Thymosin β4 peptide in specific formulations (intravenous mg-level amounts for cardiac safety; 0.1% topical eye drops for corneal disease) and has studied Thymosin β4 extensively in animals at microgram quantities. It has not established a human dose for the TB-500 fragment, which has no clinical trials of its own and no approval from the MHRA, EMA or FDA. The reported figures above describe scientific studies and specific drug candidates — they are not a personal dosing recommendation.
References
- Malinda KM, Goldstein AL, Kleinman HK, et al. Thymosin β4 accelerates wound healing. Journal of Investigative Dermatology. 1999;113(3):364–368. PubMed: PMID 10469335.
- RegeneRx Biopharmaceuticals. A Study of the Safety and Efficacy of Injectable Thymosin β4 (RGN-352) for Treating Acute Myocardial Infarction. ClinicalTrials.gov: NCT01311518.
- Sosne G, Dunn SP, Kim C. Thymosin β4 significantly improves signs and symptoms of severe dry eye in a phase 2 randomized trial. Cornea. 2015;34(5):491–496. PubMed: PMID 25826322.
- Sosne G, et al. 0.1% RGN-259 (Thymosin β4) Ophthalmic Solution in neurotrophic keratopathy: a randomized, placebo-controlled, double-masked Phase 3 clinical trial. PMC. Available: PMC9820614.