What is Thymosin Beta-4 (TB-4)?

Thymosin Beta-4 is a naturally occurring 43-amino acid peptide found in many cells throughout the body. It is one of the more abundant intracellular proteins in mammalian cells and has been a subject of laboratory research, particularly regarding its role in cell structure and movement through its interaction with actin.

What is the difference between TB-4 and TB-500?

TB-4 (Thymosin Beta-4) refers to the full naturally occurring 43-amino acid peptide. TB-500 is the name commonly used for a synthetic peptide fragment that corresponds to a portion of the TB-4 sequence. The two terms are often discussed together in peptide literature but are not identical molecules.

Where do your peptides come from?

Your prescription is filled by a licensed U.S. 503A compounding pharmacy and prepared for you specifically after your provider consultation. We do not sell research-grade or gray-market peptides.

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Important Information

TB-500 (thymosin beta-4) is not currently FDA-approved, although in July 2026 an FDA advisory committee voted to recommend allowing licensed pharmacies to compound it. At Cienega it is available by prescription only as part of combination peptide blends (such as BPC-157/TB-500), when appropriate, after a consult with our medical team. This page is for general education and is not medical advice.

What Is Thymosin Beta-4?

Thymosin Beta-4 (TB-4) is a naturally occurring 43-amino-acid peptide found in many cells throughout the body, and among the more abundant proteins inside mammalian cells. A synthetic fragment sold as TB-500 corresponds to part of the TB-4 sequence. It is studied in cell biology, including how cells move and repair. TB-500 is not currently FDA-approved; in July 2026 an FDA advisory committee voted to recommend allowing licensed pharmacies to compound it. At Cienega it is available by prescription only, as part of combination peptide blends, after a consult.

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What is Thymosin Beta-4 (TB-4)?
Thymosin Beta-4 is a naturally occurring 43-amino acid peptide found in many cells throughout the body. It is one of the more abundant intracellular proteins in mammalian cells and has been a subject of laboratory research, particularly regarding its role in cell structure and movement through its interaction with actin.
What is the difference between TB-4 and TB-500?
TB-4 (Thymosin Beta-4) refers to the full naturally occurring 43-amino acid peptide. TB-500 is the name commonly used for a synthetic peptide fragment that corresponds to a portion of the TB-4 sequence. The two terms are often discussed together in peptide literature but are not identical molecules.
Is Thymosin Beta-4 (TB-500) FDA-approved?
Not yet. Neither Thymosin Beta-4 nor the synthetic fragment TB-500 is currently approved by the U.S. Food and Drug Administration. In July 2026, however, an FDA advisory committee voted to recommend allowing licensed pharmacies to compound TB-500, and that recommendation is now in the FDA's formal review process. Until then, these remain research compounds available by prescription only.
Where do your peptides come from?
Your prescription is filled by a licensed U.S. 503A compounding pharmacy and prepared for you specifically after your provider consultation. We do not sell research-grade or gray-market peptides.