Compounds / TB-500
TB-500
Also known as: TB-500; Thymosin Beta-4 Fragment; Ac-LKKTETQ; TB-500 acetate; TB4 fragment (17-23); PubChem CID 16133418
Primary research focus: Tissue repair and wound-healing research (actin-binding fragment of thymosin beta-4)
Last updated July 2026 · Reviewed against FDA labeling and published research.
What is TB-500?
TB-500 is a synthetic seven-amino-acid peptide (Ac-LKKTETQ) corresponding to residues 17 to 23 of thymosin beta-4, the actin-binding domain of that naturally occurring 43-amino-acid protein. It is widely used in tissue-repair and wound-healing research and is frequently paired with BPC-157. A critical distinction: TB-500 is not full-length thymosin beta-4, and the clinical data generated with the full protein do not transfer to the fragment. It is not FDA-approved, and its compounding status is being decided at an FDA advisory committee meeting on July 23, 2026.
Thymosin beta-4 is the major actin-sequestering protein in mammalian cells, and the LKKTETQ motif is its central actin-binding domain. TB-500 is proposed to reproduce that activity: binding G-actin, regulating actin polymerization, and thereby promoting cell migration, angiogenesis, and tissue remodeling, with reported anti-inflammatory and anti-fibrotic effects in animal models. The acetylated N-terminus slows enzymatic breakdown. Importantly, the mechanistic picture is largely extrapolated from full-length thymosin beta-4 rather than established for the fragment itself, and FDA reviewers have noted that TB-500 is not physically and chemically well-characterized, citing inconsistent naming conventions across INN, USAN, and IUPAC and missing characterization data specific to each form.
How it’s supplied
Not an FDA-approved or commercially manufactured medicine. It is sold as a research-grade lyophilized peptide for reconstitution and has been prepared by compounding pharmacies during periods when that was permitted. Research-grade products are not FDA-reviewed for identity, potency, or sterility.
Dosage Chart
Units shown are for a U-100 insulin syringe (100 units = 1 mL), calculated from the vial size and BAC water you select. Always confirm against your prescription and your syringe markings.
| Phase | Dose | Frequency | Notes |
|---|---|---|---|
| Weeks 1-2 | 250mcg | 1x Daily | — |
| Weeks 3-4 | 500mcg | 1x Daily | — |
| Weeks 5-8 | 750mcg | 1x Daily | — |
| Weeks 9-12 | 1mg | 1x Daily | — |
- Rotate injection sites to reduce irritation and lipohypertrophy
- Not for use during pregnancy or breastfeeding
- Do not exceed the recommended dose to try to speed results
Potential Benefits and Side Effects
Effects reported in published research. Not a promise of results, and not medical advice.
- Reported in preclinical (animal and cell) research; human efficacy is not established and no completed human trials exist.
- Promotion of cell migration, angiogenesis, and tissue remodeling via actin regulation in animal models.
- Reported wound-healing and soft-tissue repair effects in preclinical models.
- Reported anti-inflammatory and anti-fibrotic properties.
- Used clinically in veterinary medicine contexts.
- Frequently combined with BPC-157 in practitioner protocols, described as complementary (musculoskeletal versus gut and systemic repair), though this is not trial-validated.
- No robust human adverse-effect data are available.
- Preclinical studies report few observed side effects, but human tolerability, immunogenicity, and long-term safety are not established.
- Theoretical concern regarding angiogenesis and cell migration in the presence of malignancy.
- Practical risks include variable identity, purity, and sterility of research-grade material.
Warnings and contraindications
Important safety information. This is not exhaustive — read the full prescribing information and consult your prescriber or pharmacist.
- No FDA-approved labeling exists; the following reflect the compound's status and the limits of its evidence, not established label warnings.
- There are no completed, published human randomized controlled trials of TB-500 for any musculoskeletal or tissue-repair indication; the evidence is preclinical.
- Ahead of the July 23, 2026 advisory committee meeting, the FDA proposed that TB-500 (free base) and TB-500 acetate not be added to the 503A bulks list, finding no adequate effectiveness or safety evidence for wound healing and concluding that both forms are not physically and chemically well-characterized; legal access through compounding may end.
- TB-500 is prohibited at all times in sport under Section S0 (Non-Approved Substances) of the WADA Prohibited List, with reported detection windows of roughly 30 to 45 days, and it is separately prohibited in horse racing.
- Australia and New Zealand classify TB-500 as a prescription medicine, and many other countries treat it as an unapproved substance; crossing borders with it carries customs risk.
- Promotion of cell migration and angiogenesis raises a theoretical concern in the presence of malignancy.
- Research-grade material varies in identity and purity; safety in pregnancy and breastfeeding has not been studied.
- Not established; no FDA-approved labeling. Precautionary considerations include active or suspected malignancy (given proposed angiogenic and cell-migration effects), known hypersensitivity, and use by athletes subject to anti-doping rules.
Reconstitution Steps
How to prepare the lyophilized vial. Confirm specifics with your pharmacist or prescriber.
- Confirm the amount of peptide in the vial and the volume of diluent you intend to use before starting.
- Wash your hands and gather supplies: the lyophilized vial, the diluent (typically bacteriostatic water), an alcohol swab, and a sterile syringe.
- Let the vial and diluent reach room temperature if they were refrigerated or frozen.
- Wipe the rubber stopper of both the peptide vial and the diluent vial with a fresh alcohol swab and let them air dry.
- Draw the intended diluent volume into the syringe.
- Insert the needle into the vial and slowly release the diluent down the inside wall rather than directly onto the powder, to avoid foaming.
- Do not shake. Gently swirl or roll the vial until fully dissolved.
- Inspect the solution: it should be clear and colorless with no visible particles. Do not use if cloudy or containing particles.
- Note the resulting concentration (amount divided by diluent volume) so it matches the reconstitution calculator on this page.
- Label the vial with the reconstitution date and store as directed under reconstituted storage.
US regulatory status
Classifications are public record but can change. For reference only, not legal advice.
Development: Thymosin beta-4 is a naturally occurring 43-amino-acid protein present in nearly every human and animal cell except red blood cells, and it has a meaningful research base including clinical trial data in corneal wound healing and venous ulcers. TB-500 is a different molecule: the synthetic acetylated fragment covering residues 17 to 23, with a different chemical identity, pharmacokinetic profile, and regulatory history, and the full-length protein's clinical data do not transfer to it. The fragment first drew analytical attention in horse-racing doping cases in the early 2010s, when laboratories needed to distinguish the synthetic version from endogenous thymosin beta-4. Animal wound-healing data exist using both the full protein and short actin-binding fragments, but as of 2026 no completed, published human efficacy trials of TB-500 itself have been reported. Regulatory movement in 2026: TB-500 (free base and acetate) was placed in Category 2 in September 2023, removed from Category 2 in the FDA's revised 503A document of April 15, 2026, and listed in an April 16, 2026 Federal Register notice for review at the Pharmacy Compounding Advisory Committee meeting on July 23, 2026, with wound healing as the nominated use. In its pre-meeting materials the FDA proposed that TB-500 not be added to the 503A bulks list.
Notes: TB-500 is not FDA-approved for any human use. Its compounding status is unsettled: it was removed from Category 2 in April 2026 but was not placed in Category 1, leaving it in a gray zone pending Pharmacy Compounding Advisory Committee review scheduled for July 23, 2026, with wound healing as the nominated use. Ahead of that meeting the FDA proposed that TB-500 (free base) and TB-500 acetate not be added to the 503A bulks list, citing no adequate effectiveness or safety evidence and inadequate physical and chemical characterization of both forms; the committee vote and final FDA determination will settle the question, so verify against the current FDA list. TB-500 is prohibited at all times in sport under WADA Section S0 and in horse racing. Australia and New Zealand classify it as a prescription medicine. It is not a controlled substance in the US. (Status current as of mid-2026.)
International status
Pharmacokinetics
Storage and handling
Important Notes
Practical considerations for consistency and safety.
- TB-500 is NOT full-length thymosin beta-4. It is the 7-amino-acid fragment Ac-LKKTETQ covering residues 17 to 23; the clinical data for the 43-amino-acid protein (corneal wound healing, venous ulcers) do not transfer to it.
- Its compounding status is actively being decided: the FDA has proposed NOT adding it to the 503A bulks list ahead of the July 23, 2026 advisory committee meeting; verify the current classification.
- FDA reviewers concluded TB-500 is not physically and chemically well-characterized, citing inconsistent naming and missing data; sources also confuse it with Ac-SDKP and misstate its length as 17 amino acids.
- It is banned in sport (WADA S0, detection roughly 30 to 45 days) and in horse racing, and is a prescription medicine in Australia and New Zealand.
- It is commonly paired with BPC-157 in research and practitioner protocols; that combination is not validated in human trials.
Lifestyle Factors
- Studied in research contexts by subcutaneous or intramuscular injection, often in loading-then-maintenance patterns.
- Human lifestyle interactions are not characterized.
References
Related compounds
Important disclaimer
This page is an educational reference, not medical advice, a diagnosis, or a treatment recommendation, and not a substitute for your prescriber or pharmacist. Approval and regulatory status varies by compound and can change. Always confirm against current prescribing information and consult a qualified healthcare professional before making any decision about a medication.