Bones & muscles Synthetic Tβ4 fragment
TB-500
Regulatory status
Status at a glance
503A compounding status
Advisory committee voted to include
FDA’s Pharmacy Compounding Advisory Committee (PCAC) voted in favor of adding this substance to the 503A bulks list. PCAC votes are non-binding recommendations; FDA and HHS make the final decision, and the substance is not on the bulks list unless FDA adds it.
- Also known as
- the Thymosin Beta-4 Fragment
- FDA approval
- Not FDA-approved for any use
- 503B outsourcing
- Not determined
- Anti-doping (WADA)
- On the WADA Prohibited List
- DEA schedule
- Not a controlled substance
About peptide status
Most peptides discussed here are not FDA-approved for any use, and products labeled “research use only” are not for human use. Removal from Category 2 does not authorize compounding. PCAC votes are non-binding recommendations; FDA and HHS make the final decisions.
This is not medical or legal advice, and we do not publish dosing, sourcing or reconstitution information. Talk with a licensed clinician before using any peptide.
If you think you are having a medical emergency, call 911.
Key takeaway
TB-500 is a synthetic fragment marketed as a "thymosin beta-4 fragment" for injury recovery, and it is banned in sport. No human trial of the fragment exists. The best controlled human data belong to the full-length protein: a Phase III eye-drop trial in neurotrophic keratopathy. TB-500 is not FDA-approved, though a 2026 advisory committee voted 8-6 to recommend it for compounding.
At a glance
- FDA status
- Not FDA-approved, sold in the wellness/gray market
- What it is
- Marketed as a synthetic fragment of thymosin beta-4, for recovery and soft-tissue injury
- Research
- No human trials of the fragment; claims are extrapolated from the full-length protein
- Sport and FDA
- Prohibited in sport by WADA at all times; a 2026 FDA advisory vote was favorable but non-binding
- Evidence strength
- Low research
Summary
TB-500 is a synthetic thymosin beta-4 fragment sold as a research peptide. Learn what the evidence shows, why it is banned in sport, and its regulatory status.
What is TB-500?
TB-500 is a synthetic peptide sold for recovery and injury repair, commonly described as the actin-binding fragment of the natural protein thymosin beta-4 (a short piece of that larger molecule, not the full 43-amino acid protein). An important caveat is that gray-market labeling is inconsistent: material sold as "TB-500" sometimes contains the full-length protein or other fragments. It is not an approved medicine.
How does it work?
TB-500 is assumed to share the actions of full-length thymosin beta-4, namely:
- Binding the cell-structure protein actin
- Promoting cell migration
- Promoting blood-vessel formation
- Promoting reduced inflammation
A review of the full-length protein's regenerative biology adds the mobilization of stem and progenitor cells and less scarring, across skin, eye, heart, and brain repair models. Importantly, this is largely extrapolated from the full-length protein's animal data; the fragment itself has far less dedicated study. This describes a proposed mechanism, separate from demonstrated benefit in people.
Is it FDA-approved?
Safety note
Status: Not FDA-approved, sold in the wellness/gray market
Category: Wellness and performance · Primary body area: Bones & muscles
No. TB-500 is not approved by the FDA. As neutral regulatory facts: On July 23, 2026, the FDA's Pharmacy Compounding Advisory Committee voted 8-6, with one abstention, to recommend TB-500 (free base and acetate) for the 503A compounding list, citing wound healing. But, because that vote is only a recommendation and FDA adoption is pending, TB-500 is not currently on the list and cannot be legally compounded on that basis. The same coverage of the meeting lists TB-500 among the peptides voted on and does not list full-length thymosin beta-4. In sport, it is treated as thymosin beta-4 and is prohibited at all times under the WADA list.
What does the research show?
Editor’s note
Evidence strength: Low research
There are no human efficacy or safety trials of the fragment itself; the claims rest on extrapolation from the full-length protein's preclinical work.
There is essentially no human evidence for the fragment. There are no completed human efficacy trials of the TB-500 fragment, and human safety data specific to it are not published. The only clinical data belong to the full-length protein, thymosin beta-4, which has been tested only in small, early trials, such as a randomized dose-escalation venous-ulcer study designed to assess safety and tolerability, and a Phase III eye-drop trial in neurotrophic keratopathy. Those results do not directly transfer to the fragment. So the marketed recovery benefit is unproven in people.
Sources: the human evidence for the related full-length protein is limited to small early trials (for example Guarnera et al., Annals of the New York Academy of Sciences, 2007, DOI: 10.1196/annals.1415.003), indexed on PubMed; reporting on the July 2026 FDA advisory committee vote; and the WADA Prohibited List. This document is educational, is not medical advice or a health claim, and is not an offer to sell any product.
Registered human trials
0 registered human trials on ClinicalTrials.gov that we reviewed
Sources
- [1]
- [2]
- [3]
- [4]
- [5]
- [6]
- [7]
- [8]
- [9]
- [10]
Compare every peptide’s status in the peptide regulatory status database
More for Bones & muscles
View all bones & muscles peptides →- FDA-approved Bones & muscles
Abaloparatide
Abaloparatide is a synthetic 34-amino acid analog of parathyroid hormone-related protein (PTHrP) that activates the PTH1 receptor to stimulate new bone formation. FDA-approved in 2017 as Tymlos, it is a daily injection for postmenopausal women and men with osteoporosis at high fracture risk, and it is capped at two years of use. In the pivotal ACTIVE trial, it cut the risk of new spine fractures by about 86% versus placebo.
- FDA-approved Bones & muscles
Calcitonin-Salmon
Miacalcin (injection), nasal spray sold as a generic
Calcitonin-salmon is an FDA-approved synthetic version of a natural hormone that slows bone breakdown, used mainly for postmenopausal osteoporosis, Paget's disease of bone, and high blood calcium (hypercalcemia). It comes as an injection, sold as Miacalcin, and as a nasal spray sold as a generic. A modest effect on fractures and a small possible cancer risk with long-term use make it a second-line option today.
- Not FDA-approved Bones & muscles
Cjc-1295
CJC-1295 is a synthetic long-acting analog of growth-hormone-releasing hormone (GHRH). In two placebo-controlled trials of healthy adults aged 21 to 61 (Teichman, 2006), a single injection raised mean growth hormone 2- to 10-fold for 6 days or more. Mean IGF-1 rose 1.5- to 3-fold, but no controlled human trial shows benefit for muscle, fat loss, recovery, or anti-aging. CJC-1295 is not FDA-approved, it is not eligible for routine pharmacy compounding, and it is banned in sport.
- FDA-approved Bones & muscles
Etelcalcetide
Etelcalcetide (sold as Parsabiv) is a peptide that activates the calcium-sensing receptor to lower parathyroid hormone, used for secondary hyperparathyroidism in people on dialysis for kidney disease. Unlike parathyroid hormone replacement, it suppresses an overactive parathyroid signal, and it is given intravenously at the end of each dialysis session. It has been FDA-approved in the U.S. since 2017.
- Not FDA-approved Bones & muscles
Follistatin-344
Follistatin-344 is a form of the natural protein follistatin that blocks myostatin, a brake on muscle growth, sold as a "research chemical" in the performance market for muscle gain. The strongest human data come from gene therapy, not the injectable peptide. In a small 2017 trial, six patients with sporadic inclusion body myositis gained a median 56.0 m per year on the 6-minute walk test after follistatin gene therapy, versus a 25.8 m decline in eight matched untreated controls (p = 0.01). It is not FDA-approved and is banned in sport.
- Not FDA-approved Bones & muscles
Ghrp-2
Pralmorelin
GHRP-2 (pralmorelin) is a synthetic ghrelin-mimic peptide that prompts the pituitary to release growth hormone, sold in the wellness market for muscle, recovery, and appetite. Its only genuine validated use is as a diagnostic test of growth hormone capacity (approved in Japan), not as a treatment, and there are no controlled trials supporting the marketed wellness benefits. As of 2026 it is not FDA-approved and is banned in sport.