Side-by-side evidence
Outcomes where both peptides have published data. Each cell carries two grades: clinical evidence (human-RCT depth for this specific outcome) and community evidence (real-world adoption). How we grade evidence.
Actin-binding / cell migration
7-amino-acid active fragment (Ac-LKKTETQ) carries the actin-binding motif.
Full 43-amino-acid peptide; activates the complete native signaling cascade including secondary domains.
Tendon and tissue healing (rodent)
Improved tendon repair and tensile strength in rodent models.
Similar healing effect plus broader signaling; data overlap with TB-500 in most studies.
Cost per mg
Lower per-mg cost — the smaller fragment is cheaper to synthesize.
Significantly more expensive per mg due to longer synthesis and lower availability.
Human clinical evidence
No completed RCTs.
Early-phase trials in dry-eye and post-MI; otherwise data overlap with TB-500.
Parent Peptide vs Active Fragment
Thymosin Beta-4 (TB-4) is the full 43-amino acid endogenous peptide. TB-500 is a synthetic fragment of TB-4 — specifically the 7-amino acid active region (Ac-LKKTETQ, residues 17–23) responsible for actin binding and cell migration signaling.
This is one of the most frequently asked questions in peptide research. They are related but not interchangeable.
For a complete deep dive into TB-4, see our Thymosin Beta-4 Research Guide.
Mechanism Comparison
TB-4 (Full Peptide)
TB-4 is the body's primary actin-sequestering molecule. As the full-length peptide, it activates the complete native signaling cascade:
Actin sequestration — maintains G-actin reservoir for cell migration
Angiogenesis — upregulates VEGF for new blood vessel formation
Anti-inflammatory — reduces IL-1β and TNF-α
Progenitor cell activation — mobilizes epicardial and satellite stem cells
Anti-fibrotic — reduces excessive scar tissue formation
TB-4 provides the full biological context — some downstream effects may require the complete peptide sequence.
TB-500 (Fragment)
TB-500 contains the core active region of TB-4. It retains the primary mechanism but in a smaller, more stable package:
Actin binding — same core LKKTETQ motif that drives cell migration
Cell migration signaling — promotes fibroblast and keratinocyte movement
Enhanced stability — smaller molecule degrades less readily
Superior distribution — penetrates tissues more easily due to lower molecular weight
TB-500 may lack some of TB-4's broader signaling — particularly the full progenitor cell activation cascade — but delivers the core repair signal more efficiently.
Quick Comparison Table
Structure
43 amino acids (full peptide)
7 amino acids (active fragment)
Molecular weight
~4,921 Da
~843 Da
Origin
Endogenous — naturally produced
Synthetic — lab-manufactured
Stability
Lower (larger molecule)
Higher (smaller, more resistant)
Tissue distribution
Broad (carried by platelets)
Extremely broad (small molecule diffusion)
Core mechanism
Complete actin + multi-pathway
Targeted actin-binding & migration
Progenitor cell activation
Yes (full cascade)
Unclear (may be partial)
Anti-fibrotic
Strong evidence
Extrapolated from TB-4 data
Published research
Extensive (Nature, PNAS, etc.)
Limited direct studies
Cost
Higher
Lower
Typical dose
2–5 mg, 2x/week
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