Compound Profile
TB 500
Synthetic thymosin beta-4 fragment
TB 500 is a synthetic fragment of thymosin beta 4 marketed for muscle recovery and connective tissue repair; the underlying Tβ4 biology has real scientific grounding, but the synthetic fragment sold as TB 500 has thin direct human evidence and an unresolved FDA compounding status pending July 2026 PCAC review.
Last reviewed:
C PreliminaryMonograph visual
TB 500
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Unapproved compound: FDA compounding status pending review
TB-500 is not FDA-approved for human use. It was removed from the FDA’s Category 2 restricted 503A bulk substances list in April 2026, but remains in a regulatory gray zone pending the FDA Pharmacy Compounding Advisory Committee’s (PCAC) scheduled July 23, 2026 review.
- Research-use-only (RUO) product is not legally intended for human consumption.
- No completed human clinical trials exist for the synthetic TB-500 fragment specifically.
- This profile is not a self-treatment guide.
Regulatory status
2026 federal and state regulatory context
Not FDA approved for human use; RUO labeled product is not legally intended for human consumption.
Regulatory changelog
- 2023 04/2026: FDA Category 2 restricted (503A bulk substances), alongside BPC 157 and 17 other peptides. 2026 04: Removed from Category 2 (gray zone). 2026 07 23: On FDA PCAC agenda alongside BPC 157, KPV, and MOTS C for formal 503A eligibility review.
Quick Stats
Evidence level
Preliminary evidence
Typical onset
Varies by prep
Safety rating
Use extra caution: Use caution
Best for
Actin (G Actin) Binding, Cell Migration Promotion, Angiogenesis Support
Avoid / review if
Pregnancy/Breastfeeding, Unsupervised RUO Product Use Without Physician Oversight, No Established Pharmacokinetic Drug Interaction Data Exists
Safety & Cautions
Review before use if any apply: Pregnancy/Breastfeeding, Unsupervised RUO Product Use Without Physician Oversight, No Established Pharmacokinetic Drug Interaction Data Exists.
Evidence Summary
C PreliminaryEvidence lens
Early signal that needs stronger human replication before practical claims.
Human clinical evidence: Not the primary signal
Mechanistic / preclinical: Mechanism mapped — Actin (G Actin) Binding · Cell Migration Promotion · Angiogenesis Support
Research maturity: Preliminary or mixed — main contexts: Actin (G Actin) Binding · Cell Migration Promotion · Angiogenesis Support
Safety boundary: Safety note available — Review before use if any apply: Pregnancy/Breastfeeding, Unsupervised RUO Product Use Without Physician Oversight, No Established Pharmacokinetic Drug Interaction Data Exists.
Confidence estimate based on the design quality and consistency of published clinical trials.
TB 500 has a preliminary evidence evidence rating.
How evidence grades work
Each grade reflects the strength and consistency of published human evidence — not marketing claims. Grades are based on study count, design quality, effect size, consistency, and recency.
Strong
Multiple RCTs, consistent direction, adequate effect size
Moderate
Some RCTs or consistent observational data in humans
Preliminary / Mixed
Animal or in-vitro only, or conflicting human data
Traditional / Theoretical
Traditional use only; no controlled human trials
How TB 500 Works
Simplified mechanism pathway based on preclinical and pharmacological evidence. Does not confirm clinical efficacy.
Mechanism Pathway — How TB 500 Works
Mechanisms & Biological Pathways▼
Preclinical mechanism details from scientific profiles; these represent plausible pathways but do not guarantee clinical efficacy in humans.
Compare & Sourcing
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Free safety checklist
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⚠️ Sourcing Options Disabled for Safety
Direct product recommendations and affiliate links are suppressed for this compound due to its high caution or needs-review safety classification.
Evaluate the safety checks, contraindications, and potential medication interactions below under clinician supervision before use.
Safety first · Harm reduction
This information is educational and not medical advice. Start low, avoid risky combinations, and consult a licensed clinician before making health decisions—especially if you use medications, have diagnosed conditions, or are pregnant/breastfeeding.
Learn how we evaluate confidence, safety, and intensity on the methodology page.
Editorial Review
Checked against primary sources, cited evidence, and contraindication language before publication. Evidence claims, safety language, and affiliate modules are reviewed independently. Not personal medical advice.
Compound profile context
How to interpret TB 500
TB 500 dosage by use case, onset and duration, safety limits, and interactions for actin (g actin) binding, graded against research. Mechanistic Evidence… Use this compound profile to understand mechanism, evidence quality, and practical safety context before comparing products or building a stack. A biochemical pathway connection can be useful for discovery, but it is not the same as proven benefit in humans.
When reviewing TB 500, separate the active molecule from the product category around it. Dose form, absorption, extract standardization, medication interactions, and individual sensitivity can change the real-world risk-benefit picture.
For supplement planning, avoid combining multiple compounds with overlapping sedating, stimulating, serotonergic, blood-pressure, anticoagulant, or liver-metabolism effects unless a qualified clinician has reviewed the context.