TB-500 dosing: what the trials used

Online discussions of TB-500 dosing routinely cite ranges like 2 to 2.5 mg twice weekly or 2 mg once weekly for maintenance. Those numbers do not come from a human clinical trial. They are community-derived estimates, assembled from vendor pages and forum threads, with no controlled trial behind them. This article traces what the published literature has actually tested, trial by trial, and explains why no defensible human dose exists for the grey-market injury-recovery use case. For the full compound profile, see the TB-500 peptide page.

Preclinical dose ranges in animal models

The published animal work on thymosin beta-4 (Tβ4) covers rodent and large-animal models across wound healing, cardiac repair, and corneal regeneration. Doses vary considerably depending on model and route.^[1] Goldstein, Hannappel and Kleinman reviewed the preclinical literature in 2005 and described systemic and topical Tβ4 application in dermal wound-healing and cardiac post-infarct rodent models, but the full-text protocols report doses across a wide range, typically from micrograms per kilogram to low milligrams per kilogram administered by intraperitoneal, intramuscular or direct local injection.

Philp and Kleinman's 2010 review of animal studies with thymosin beta similarly described work across dermal, corneal and cardiac models without settling on a single canonical dose, because the models used different routes, frequencies and total durations^[2]. The consistent picture across the preclinical literature is that Tβ4 produces measurable tissue-repair effects in rodents across a broad dose range, but that those dose figures were chosen to demonstrate biological activity in a given model, not to identify a therapeutic window for humans.

The first registered human trial: Ruff et al., 2010

The earliest randomised, controlled human study of systemic thymosin beta-4 was a Phase I intravenous dose-escalation trial in healthy volunteers, reported by Ruff, Crockford, Girardi and Zhang in the Annals of the New York Academy of Sciences in 2010^[3]. Four cohorts of ten participants each received ascending single intravenous doses of 42, 140, 420, or 1260 mg of synthetic Tβ4. A separate multiple-dose arm then administered the same doses once daily for 14 days.

Adverse events across all four dose levels were infrequent and mild or moderate in intensity. The investigators reported no dose-limiting toxicities and no serious adverse events at any dose, including at the highest single dose of 1260 mg^[3]. Pharmacokinetics showed a dose-proportional response and an increasing half-life with increasing dose. The compound was well tolerated and the authors recommended further cardiac-ischaemia development. That programme did not advance to Phase 2.

Phase I pharmacokinetics in Chinese healthy volunteers: Wang et al., 2021

A separate Phase I programme by Wang and colleagues, published in the Journal of Cellular and Molecular Medicine in 2021, studied recombinant human thymosin beta-4 administered intravenously to healthy Chinese volunteers^[4]. The single-dose part enrolled 54 subjects across seven cohorts at doses of 0.05, 0.25, 0.5, 2.0, 5.0, 12.5 and 25.0 mcg/kg. The multiple-dose part enrolled 30 subjects across three cohorts at 0.5, 2.0 and 5.0 mcg/kg administered once daily for 10 days.

As in the Ruff trial, no dose-limiting toxicities were observed^[4]. Plasma concentration and area under the curve rose proportionally with dose, and there was no obvious accumulation over the 10-day multiple-dose arm. The investigators concluded the safety profile supported advancing the compound toward acute myocardial infarction trials.

Topical trials: pressure ulcers and ophthalmic use

Alongside the intravenous safety work, two topical programmes generated human trial data. A RegeneRx-sponsored Phase 2 topical trial in pressure ulcers (NCT00382174) completed in December 2008. Participants received once-daily topical thymosin beta-4 at 0.01%, 0.02% or 0.1% concentration for up to 84 days, or placebo. Of 72 enrolled participants, 11 achieved complete healing by day 84^[5]. The results suggested limited efficacy for this indication at those topical doses, and the programme did not advance beyond Phase 2.

The ophthalmic programme, run by RegeneRx and the ReGenTree joint venture, is the only Tβ4 clinical programme to have produced a positive Phase 3 result. The 2023 neurotrophic keratopathy trial used a 0.1% Tβ4 ophthalmic solution (RGN-259), not an injection. Complete corneal healing at four weeks occurred in 6 of 10 treated patients compared with 1 of 8 on placebo. For context on that programme, see the TB-500 peptide page.

A 2026 Phase 1/2 trial using the heptapeptide fragment

As of early 2026, an industry-sponsored Phase 1/2 trial (NCT07487363) is recruiting participants with stable atherosclerotic cardiovascular disease to receive TB-500 in its strict sense, the AC-LKKTETQ heptapeptide fragment corresponding to amino acids 17 to 23 of full-length Tβ4, administered in sequential dose cohorts over eight weeks^[5]. The primary endpoints are safety and serious adverse event rates at 12 weeks. Specific dose levels are defined in the protocol but are not publicly disclosed in the registry entry. Secondary endpoints include measures of vascular function such as flow-mediated dilation and pulse wave velocity. This trial is the first registered study of the heptapeptide itself, distinct from the full-length Tβ4 used in the Ruff and Wang trials and in the RegeneRx ophthalmic programme.

Why no standard dosing exists

The published human safety trials and registered programmes cover four distinct formulations and routes: high absolute milligram intravenous doses (Ruff 2010), low mcg/kg intravenous doses (Wang 2021), topical gel (NCT00382174), 0.1% ophthalmic solution (RGN-259), and undisclosed heptapeptide doses by injection (NCT07487363). None was designed for, or is applicable to, subcutaneous injection of grey-market TB-500 for tendon, ligament or muscle injury. They establish that full-length Tβ4 is tolerable at the intravenous doses tested. They do not establish a subcutaneous dose, a therapeutic window, or safety data for repeated self-injection.

The 2 to 2.5 mg range cited online has no Phase 1 trial behind it. It derives from allometric conversion of animal doses and from community repetition of vendor recommendations.

What the literature still does not tell us

The published dataset leaves several questions open. There is no completed Phase 2 or Phase 3 trial of systemic Tβ4 or TB-500 for any musculoskeletal or injury-recovery indication. There is no characterised human dose-response relationship for subcutaneous injection. There is no long-term safety dataset for repeated dosing outside the 14-day multiple-dose window studied by Ruff et al. There is no pharmacokinetic characterisation of the grey-market heptapeptide AC-LKKTETQ by the subcutaneous route in humans. And the NCT07487363 heptapeptide cardiovascular trial, which is the first registered study using the compound most grey-market products actually contain, has not yet reported results. The FDA's Pharmacy Compounding Advisory Committee is scheduled to review TB-500 at its 23 to 24 July 2026 meeting, but that review addresses the compounding question, not the missing efficacy and safety data^[6].

This article is educational. It does not recommend any dose of TB-500 or thymosin beta-4. Any decision about whether to use an investigational peptide belongs with a clinician who knows your medical history.