TB-500 (Ac-LKKTETQ) is a synthetic derivative of thymosin beta-4 consisting of the N-terminal acetylated 17-23 amino acid fragment. This sequence represents the active site within thymosin beta-4 responsible for actin binding, cell migration, and wound healing. Research shows it promotes endothelial cell differentiation, angiogenesis, keratinocyte migration, collagen deposition, and decreases inflammation. The acetylation protects against N-terminal degradation while maintaining biological activity.

Mechanism of Action

TB-500 contains the LKKTETQ sequence which is the actin-binding motif of full-length thymosin beta-4. This fragment shares many properties of the parent protein regarding cell proliferation, differentiation, and migration. It promotes angiogenesis by upregulating VEGF expression and enhancing endothelial cell sprouting. The peptide undergoes serial cleavage at the C-terminus during metabolism, while the N-terminal acetylation provides protection from degradation.

Reconstitution Calculator

Safety Profile

Safety Profile: TB-500 Fragment (Ac-LKKTETQ)

Common Side Effects

• Injection site reactions: pain, redness, swelling, and bruising
• Headache and mild fatigue post-injection
• Mild nausea
• Lightheadedness and transient hypotension
• Localized warmth at injury sites (consistent with enhanced healing response)

Serious Adverse Effects

• Very limited human safety data: TB-500 (thymosin beta-4 fragment) has not completed rigorous clinical trials for most marketed indications
• Theoretical cancer risk: Thymosin beta-4 promotes angiogenesis and cell migration; could theoretically support tumor growth or metastasis in individuals with existing malignancies
• Infection risk from non-sterile injection practices (reconstituted peptide, gray-market sourcing)
• Unknown long-term effects of exogenous thymosin beta-4 fragment administration
• Potential for immune modulation with unpredictable consequences

Contraindications

• Active cancer or history of cancer (angiogenic and cell-migration-promoting properties)
• Active infections (immune modulation may complicate infection control)
• Pregnancy and lactation (unknown effects on fetal development)
• Children and adolescents (effects on growth and development unknown)
• Known hypersensitivity to thymosin beta-4 or related peptides

Drug Interactions

• Immunosuppressants: TB-500's immune-modulating effects may alter drug efficacy
• Anticoagulants: Potential for altered wound healing and bleeding dynamics
• Growth factors and other peptides (BPC-157, GH secretagogues): Often stacked by users, but combined effects are unstudied
• Chemotherapy agents: Contradicted due to angiogenic and proliferative effects

Population-Specific Considerations

• Athletes and equine medicine: Most commonly used for soft tissue injury recovery; popular in horse racing (where it is banned) and among athletes
• Gray-market sourcing: Quality, purity, and sterility cannot be guaranteed; contamination and mislabeling are common
• Research peptide status: Not FDA-approved for any human indication; all human use is experimental
• Wound healing: Primary proposed benefit; some animal and in vitro data support acceleration of healing, but human clinical evidence is limited
• Dosing: No established protocol; user-reported regimens vary widely (2–5 mg subcutaneous 1–2x weekly)

Pharmacokinetic Profile