Dosage research on TB-500

Preclinical research dose ranges

In published preclinical research on thymosin β4 (the parent peptide whose active fragment is TB-500), administered dose ranges in rodent models have most commonly fallen in the 6 to 24 milligram per kilogram range delivered intraperitoneally or intravenously. The cardiac-repair literature (murine left-anterior-descending-coronary-artery infarct models) reports doses in this range across multi-day protocols. The corneal wound-healing literature has used topical concentrations in the 0.1 to 0.5 percent range applied to the ocular surface across daily-dosing protocols.

The dermal wound-healing literature has used a range of doses depending on the study design. Topical application of thymosin β4 in murine models has appeared at concentrations between 0.01 and 1 percent in the published work, with subcutaneous and intraperitoneal administration appearing at doses between 1 and 12 milligrams per kilogram in models examining systemic effects on wound bed remodeling. The venous-ulcer human-pilot literature (a clinical-pilot rather than Phase 1 dose-ranging context) examined topical concentrations of 0.01 to 0.03 percent applied to the wound surface daily.

The vascular and angiogenesis literature has used both bolus intravenous administration (typically 100 to 200 microgram per dose in mouse hind-limb-ischaemia models) and chronic intraperitoneal administration at lower doses for time-course studies. The pharmacokinetic profile in rodent studies reports a short circulating half-life with reported sequestration of the peptide into intracellular compartments where the actin-binding chemistry plays out.

Dose-response considerations from the published literature

The published thymosin β4 literature has reported dose-response characteristics that differ by model system. In the cardiac-repair literature, dose-response work has reported larger effects at the higher end of the 6 to 24 milligram per kilogram range, with the 24 milligram per kilogram dose level frequently appearing as the maximally-effective dose in murine infarct models. In the corneal wound-healing literature, dose-response work has reported plateau effects at topical concentrations above 0.5 percent.

The dermal wound-healing literature has reported dose-response characteristics that vary by route of administration. Topical-application dose-response work has reported maximum re-epithelialisation effects at the 0.1 to 0.3 percent concentration range with no additional benefit at higher concentrations. Subcutaneous and intraperitoneal administration dose-response work has reported effects scaling with dose across the 1 to 12 milligram per kilogram range.

No Phase 1 or Phase 2 dose-ranging trial of TB-500 specifically has appeared in the indexed clinical-trial literature at the time of writing. The thymosin β4 venous-ulcer human-pilot trial used topical concentrations of 0.01 to 0.03 percent applied daily, and that study is a clinical-pilot report rather than a dose-finding trial. The TB-500 research community continues to rely on the rodent in-vivo and human-pilot literature for dose-design inference.

Reconstitution math and per-vial dose calculation

A 10 mg lyophilised TB-500 vial reconstituted with 2 mL of bacteriostatic water yields a stock concentration of 5 mg per mL, which is the most common stock concentration in published rodent protocols using TB-500 from research-grade lyophilised vials. From this stock, a research aliquot of 0.1 mL contains 500 micrograms of TB-500; an aliquot of 0.04 mL contains 200 micrograms. Researchers working in the milligram-per-kilogram dose ranges reported in published rodent in-vivo experiments typically further dilute the stock to a working concentration appropriate to the model and the body weight of the animal subject. The reconstituted aliquot is refrigerated at 2 to 8 degrees Celsius, protected from light, and standard peptide-handling practice in the published literature reports stability of the reconstituted material across the experimental observation window when these storage conditions are maintained.

Research-protocol design considerations

Protocol-design choices in the published thymosin β4 / TB-500 literature reflect several recurring considerations. Dose selection in cardiac and systemic endpoints anchors at the milligram-per-kilogram range and varies with the endpoint and the model. Dose selection in topical-application dermal and ocular studies anchors at the 0.1 to 0.3 percent concentration range. Investigators designing a new study often begin at the anchor that matches their model and add comparator arms above and below to characterise the dose-response curve in their specific system.

Route of administration in the published rodent work is chosen to match the endpoint. Topical application is common for ocular and dermal endpoints. Intraperitoneal and intravenous administration are common for cardiac, hepatic, and systemic endpoints. Intramuscular administration appears in studies examining muscle-tissue endpoints and in equine veterinary research (a literature that exists separately from the rodent in-vivo work and uses different dose conventions).

Multi-day and multi-week protocols are more common than single-dose protocols in the regeneration literature, reflecting the time scale over which tissue-remodeling endpoints are measured. Acute single-dose protocols appear in the pharmacokinetic and intracellular-sequestration literature where the endpoint is measured within hours of administration. The published handling literature on TB-500 reports stability of the reconstituted material across these observation windows under standard refrigerated storage conditions.

References

1. Malinda KM et al. Thymosin β4 stimulates directional migration of human umbilical vein endothelial cells. FASEB Journal, 1997. [PMID 9194528]
2. Yarmola EG et al. Formation and implications of a ternary complex of profilin, thymosin β4, and actin. Journal of Biological Chemistry, 2001. [PMID 11579089]
3. Sosne G et al. Thymosin β4 promotes corneal wound healing and decreases inflammation in vivo following alkali injury. Experimental Eye Research, 2002. [PMID 11950239]
4. Bock-Marquette I et al. Thymosin β4 activates integrin-linked kinase and promotes cardiac cell migration, survival and cardiac repair. Nature, 2004. [PMID 15565145]
5. Guarnera G et al. Thymosin β4 and venous ulcers: clinical remarks on a European prospective, randomized study. Annals of the New York Academy of Sciences, 2007. [PMID 17495250]
6. Sosne G et al. Thymosin β4 protein therapy for cardiac repair. Annals of the New York Academy of Sciences, 2012. [PMID 22236126]
7. Sosne G et al. Thymosin β4 promotes dermal healing. Vitamins and Hormones, 2016. [PMID 27450738]
8. Treadwell T et al. Thymosin β4 induces angiogenesis in critical limb ischemia mice via regulating Notch/NF-κB pathway. International Journal of Molecular Medicine, 2020. [PMID 32945357]