TB-500 (Thymosin Beta-4) Side Effects
Critical Safety Information
TB-500 is not an FDA-approved medication for human use, and the available evidence on its side effects comes primarily from veterinary studies and analytical chemistry research rather than controlled human clinical trials. The provided evidence contains one FDA drug label, but it describes thiamine (Vitamin B1), not TB-500, which appears to be a documentation error 1.
What We Know About TB-500
Composition and Metabolism
- TB-500 contains the synthetic peptide Ac-LKKTETQ, which is an N-terminal acetylated version of the 17-23 amino acid fragment of thymosin β4 2, 3.
- The peptide is metabolized into several fragments, with Ac-LK being the primary metabolite detected at highest concentrations in the first 0-6 hours, and Ac-LKK persisting as a long-term metabolite detectable up to 72 hours 4.
- Recent research suggests that the wound-healing activity attributed to TB-500 may actually be due to its metabolite Ac-LKKTE rather than the parent compound 4.
Safety Profile from Available Research
- No cytotoxicity was observed in fibroblast cell studies of TB-500 or its metabolites 4.
- TB-500 has been detected in equine sports doping control, indicating its use (and potential misuse) in veterinary applications 2, 3.
- The compound is claimed to promote endothelial cell differentiation, angiogenesis, keratinocyte migration, collagen deposition, and decrease inflammation, though these claims lack rigorous human clinical trial validation 2.
Critical Limitations
Absence of Human Safety Data
There are no published guidelines, FDA approvals, or systematic human clinical trials documenting the adverse effects of TB-500 in humans. The evidence base consists entirely of:
- Analytical chemistry methods for detection 2, 3, 4
- In-vitro cell culture studies 4
- Veterinary/equine studies 2
Misidentification Risk
The FDA drug label provided 1 describes thiamine (Vitamin B1) adverse reactions, which include:
- Hypersensitivity reactions and life-threatening anaphylaxis (especially after repeated injections)
- Collapse and death (reported cases)
- Warmth, pruritus, urticaria, weakness, sweating, nausea, restlessness
- Throat tightness, angioneurotic edema, cyanosis, pulmonary edema
- Gastrointestinal hemorrhage
- Tenderness and induration at IM injection sites
These reactions are NOT established for TB-500 and represent a different compound entirely 1.
Clinical Recommendations
Given the complete absence of FDA approval, established safety data, or clinical guidelines for TB-500 use in humans, this compound should not be recommended for any medical indication. Patients inquiring about or using TB-500 should be:
- Counseled that this is not an FDA-approved medication for human use
- Informed that no systematic safety data exists for human administration
- Advised of the unknown risk profile, including potential for contamination or mislabeling in unregulated products
- Evaluated for underlying conditions that may have prompted their interest in this compound, with evidence-based alternatives offered
For Patients with Pre-existing Conditions
Without established pharmacokinetic, pharmacodynamic, or safety data in humans, no specific guidance can be provided for dose adjustments or contraindications in patients with renal disease, hepatic disease, pregnancy, or other medical conditions.