The TB-500 dosage data that exists in the peer-reviewed literature is preclinical — rodent intraperitoneal injection studies, equine intramuscular administration, local delivery in fibrin sealant, and one Phase I IV study of the full-length Tβ4 protein (not the TB-500 fragment) in humans.[16] No validated human dose-response study for injectable TB-500 has been published.
TB-500 Loading Phase Protocols in Research
Preclinical and equine literature most commonly references administration protocols of 2–5 mg given subcutaneously or intramuscularly, 1–2 times per week, over a 4–6 week period. This protocol is described in equine veterinary contexts where TB-500 was administered for musculoskeletal conditions, and gave rise to WADA's doping-control methodology for the compound.[18]
None of these protocols were validated in a controlled human clinical trial. They are descriptive of practice in the equine research context only. The 4–6 week window appears because most preclinical injury studies use this duration before measuring outcomes — not because it represents an evidence-based "loading" protocol for any species.
Preclinical Dose Data by Study
The following doses appear in the peer-reviewed literature for Tβ4 and TB-500 across different study types:
| Dose | Route | Species / Model | Citation |
|---|---|---|---|
5.37 mg/kg |
Intraperitoneal (IP) | Rat cardiac infarction (Sprague-Dawley); 43% infarct reduction at 28 days | [6] |
6 or 30 mg/kg |
IP | Rat TBI model (Wistar); 30 mg/kg superior for sensorimotor recovery | [7] |
2–18 mg/kg (optimal 3.75) |
IP | Rat embolic stroke model; day-56 neurological recovery | [8] |
1 µg local |
Fibrin sealant, local delivery | Rat medial collateral ligament; superior biomechanics at 4 weeks | [9] |
150 µg ×2/week |
IP, 6 months | Dystrophin-deficient mice; more regenerating fibers, no functional improvement | [11] |
12 mg/kg/day |
IP, 4 weeks | C57BL/6 mice, NAFLD; M1→M2 macrophage polarization | [22] |
0.05–25 µg/kg (IV, single) |
Intravenous | Human — full Tβ4 protein (NL005), 54 volunteers; no serious adverse events | [16] |
These doses span an enormous range across different species, routes, tissue targets, and preparation types. They do not constitute a dosing guide for any species, including rodents outside the specific protocols cited.
FIG. 04 — Half-life decay arcs
TB-500 Half-Life and Elimination
No validated half-life data exists for the TB-500 fragment (Ac-LKKTETQ) in humans following injectable administration. The available pharmacokinetic data:
Full Tβ4 protein (IV, human): Half-life 0.5–2.08 hours, Tmax 3–15 minutes, following single-dose IV administration in 54 healthy Chinese volunteers in the NL005 Phase I trial.[16] This applies to the full 43-amino-acid protein given intravenously — not the heptapeptide fragment.
TB-500 fragment (rat, injectable): A 2024 study using UHPLC-Q-Exactive Orbitrap MS/MS quantified TB-500 and its metabolites in rat plasma following injection. The primary metabolite Ac-LK peaked at 0–6 hours post-administration; the secondary metabolite Ac-LKK was detectable up to 72 hours. The metabolite Ac-LKKTE showed significant wound-healing activity in fibroblast assays. No cytotoxicity was detected for the parent compound or its metabolites.[19]
Based on these datasets, the active window for the fragment in rat plasma likely spans 6–72 hours depending on which metabolite is considered. Human pharmacokinetics for injectable TB-500 remain uncharacterized.
Administration Route: Subcutaneous vs Intramuscular
Most published preclinical studies used intraperitoneal injection — a route unique to small-animal research and not clinically relevant for humans. Subcutaneous and intramuscular administration are referenced in equine and some rodent contexts. No head-to-head human comparison of routes for TB-500 exists in the literature. Both subcutaneous and intramuscular injection are described in equine use contexts, interchangeably, without evidence of differential efficacy or safety. The full Tβ4 Phase I study used intravenous administration, pharmacokinetically distinct from subcutaneous or intramuscular routes.[16]
TB-500 Onset: What Animal Models Suggest About Timeline
In rodent wound-healing models, measurable tissue repair effects are typically assessed at 4–7 days (dermal models)[3] or 4 weeks (ligament models)[9], with the compound administered throughout. Rat metabolite data shows detectable active metabolites from 0 to 72 hours after a single injection.[19] Equine data in musculoskeletal conditions references 4–6 week administration protocols before outcome assessment. No human time-course data for wound healing, injury repair, or any other endpoint exists for TB-500.
Research-Grade TB-500 Purity and Contaminant Risks
A 2023 analytical chemistry study examined internet-marketed TB500/TB1000 products and found composition "not systematically consistent with its former descriptions."[17] Contamination risks distinct from the peptide's own pharmacology — bacterial endotoxins, incorrect peptide sequences, undisclosed excipients, heavy metals — represent independent safety hazards in research-grade preparations. The FDA's Category 2 classification of TB-500 specifically cites characterization and impurity concerns as part of its safety rationale.