At a glance

What it is

What TB-500 is, and what it is not

Thymosin beta-4 is a protein of 43 amino acids that the body makes naturally. It is found in blood, tears and wound fluid, and it helps control the protein scaffolding inside cells. TB-500 is a much smaller piece of it. FDA’s review describes TB-500 as a seven amino acid fragment, residues 17 to 23 of thymosin beta-4, with an acetyl group added at one end. Its chemical sequence is Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln.

That makes TB-500 a different substance from thymosin beta-4. Websites often use the two names as if they were the same. FDA’s reviewers pointed this out directly. You may also see TB-500 linked to Ac-SDKP online. Ac-SDKP is a different peptide, and it is not what FDA’s documents describe as TB-500.

TB-500 is a common name, not an official drug name. FDA reported that products sold under the name have differed in salt form and sometimes in the molecule itself. A patient could receive something other than what the prescriber intended. FDA also treats the plain form (free base) and the acetate salt as two separate substances.

TB-500 is not part of any FDA-approved drug, and FDA found no approved product containing it in the European Union, the United Kingdom, Canada or Australia. A veterinary version was marketed in 2011 for racehorses and greyhounds.

Evidence

What the evidence actually shows

Online sellers say TB-500 helps tendons, muscles, ligaments, scar tissue, hair, inflammation, endurance and more. None of those claims has been tested in people. The one use the FDA advisory committee looked at was wound healing.

Animal and cell studies

• In 2003, researchers put a similar peptide, the same seven amino acids without the acetyl group, on small skin wounds in aged mice. The wounds closed faster and made more collagen. That peptide was applied to the skin, not injected, and it is not identical to TB-500. The study did not test different doses.
• In a 2024 cell study that FDA cited, TB-500 itself did not close scratch wounds in a dish of skin cells. One of its breakdown products did, slightly. It is unknown whether TB-500 works in a living body, or only after it is broken down.
• A study in racehorses showed that an injected dose reaches the blood, stays for hours, and is broken down into smaller pieces. That is a drug-testing study. It did not measure healing.

Human studies

FDA searched the medical literature and found no article in which TB-500 was given to a person for any condition. It found no human pharmacokinetic data and no case reports. Its search of the adverse event database through March 2025 found no reports for TB-500. That is not a sign of safety, because reporting is voluntary and compounded products are rarely reported.

There are human studies of full-length synthetic thymosin beta-4, which is a different molecule. In one randomized trial, healthy volunteers in four groups of 10 received it by vein, once and then daily for 14 days. Side effects were infrequent and mild or moderate, with no serious events. A later review described two phase 2 trials of the full protein in leg vein ulcers and pressure ulcers, and reported faster healing in people who did heal. That was a review, not a new trial, and its results cannot be applied to TB-500.

In short: TB-500 has animal and cell data, some of it mixed, and no human data. FDA staff concluded the evidence was too thin to support adding it to the compounding list.

Safety

Safety unknowns and who should not use it

Not knowing is the main risk. FDA did not identify acute toxicity, repeat-dose toxicity, genetic toxicity, reproductive toxicity or cancer-risk studies of TB-500. The committee evaluated it with no safety record to read.

FDA’s specific concern about injected peptides is the immune system. A peptide can provoke an immune response, and that can range from no symptoms to a serious reaction. Peptides can also clump together, and impurities from manufacturing can remain in the powder. FDA noted there were no published tests for impurities, clumping, microbial quality or endotoxin for this substance. A compounded injection also depends on sterile preparation.

People who should not use it

• Anyone who is pregnant, breastfeeding or trying to conceive. Reproductive effects were never studied.
• Anyone with current cancer or a recent cancer history. No cancer-risk studies exist, so Dr. Miranda would be cautious.
• Children and teenagers.
• Anyone who has had a serious allergic or immune reaction to a peptide or injectable medicine.
• Anyone with a wound that is not healing. That needs a wound care evaluation first, since FDA-approved wound treatments exist and an injected peptide is not a substitute.
• Athletes who are drug tested.

Interactions with other medicines have not been studied. Dr. Miranda reviews your full medication list before any decision.

Sport

WADA status

The World Anti-Doping Agency prohibits thymosin beta-4 and its derivatives, including TB-500, at all times. FDA’s review cites the growth factor section of the list. Anti-doping labs developed tests for TB-500 after it appeared in sport. A tested athlete, military member or anyone under a drug-testing contract should treat it as banned. Check your own governing body’s current list.

Regulatory status

The regulatory timeline, as of November 10, 2026

Compounding is a pharmacist preparing a medicine for one patient, on a prescription. TB-500 is not on FDA’s list of bulk ingredients for this purpose. Here is how the question has moved.

• May 2026. FDA staff wrote a review of TB-500 for wound healing. It found the substance poorly characterized, no clear history of use in compounding, and no human data. It proposed not adding TB-500 to the list. The nomination that started the review had been withdrawn, and FDA reviewed it on its own initiative.
• July 23, 2026. FDA’s Pharmacy Compounding Advisory Committee voted on TB-500. Press reports give the tally as 8 to 6 in favor with 1 abstention. The vote is advice only. FDA staff had recommended against adding any of the substances under review.
• October 28 and 30, 2026. The Secretary of Health and Human Services filed, and on October 30 the Federal Register published, a notice of a draft enforcement discretion policy for six peptides: BPC-157, epitalon, KPV, MOTS-c, semax and TB-500. The National Community Pharmacists Association reported the news on October 29 and described it as FDA granting enforcement discretion. The official notice comes from HHS.
• November 13, 2026. Public comments on the draft policy close.
• Next. FDA’s formal rulemaking on the compounding list is still pending. No timeframe was given for how long the policy will last.

What the policy says, in plain words

HHS said it does not intend to take enforcement action against a state-licensed pharmacy that prepares a product from one of the six peptides. Put simply, HHS currently does not intend to act against licensed 503A pharmacies that prepare TB-500 for an individual patient under a prescription. For TB-500, the policy names the acetate form as a subcutaneous or intramuscular injectable only. The product may contain only one listed peptide, so blends are outside it. The ingredient must come from an FDA-registered manufacturer with a certificate of analysis. The label must say it is a compounded drug, and the pharmacy must report serious adverse events and quality problems.

Summit’s role

What Summit does with TB-500

Dr. Miranda decides whether this fits you after your history and labs. If he does prescribe it, an independent, state-licensed pharmacy prepares it for you as a named patient. Summit does not dispense or sell it, and it keeps no stock in the office.

Many people ask about TB-500 for an injury. Dr. Miranda will tell you plainly if another path, such as a physical therapy or orthopedic evaluation, is the better next step. Nothing on this page promises a prescription. Individual results vary, and for TB-500 there is no human evidence to predict them. See pricing for what the program includes, including labs.

Keep reading

Related medications

Sources

Where this comes from

All retrieved November 10, 2026.

1. HHS. Enforcement Discretion Policy Regarding 503A Compounding Using Certain Peptide Bulk Drug Substances, with Appendix A and B. Federal Register FR Doc 2026-22192, October 30, 2026. https://www.hhs.gov/sites/default/files/hhs-503a-peptide-enforcement-discretion-policy-appendix-b.pdf
2. FDA. Briefing document: evaluation of TB-500-related bulk drug substances for the 503A bulks list. Pharmacy Compounding Advisory Committee, July 23-24, 2026. https://www.fda.gov/media/193349/download
3. FDA. July 23-24, 2026 meeting of the Pharmacy Compounding Advisory Committee: agenda and uses evaluated. https://www.fda.gov/advisory-committees/advisory-committee-calendar/july-23-24-2026-meeting-pharmacy-compounding-advisory-committee-07232026
4. HHS. Enforcement discretion policy regarding 503A compounding using certain peptide bulk drug substances. Federal Register 91 FR 68526, October 30, 2026. https://www.federalregister.gov/documents/2026/10/30/2026-22192/enforcement-discretion-policy-regarding-503a-compounding-using-certain-peptide-bulk-drug-substances
5. NCPA. FDA grants enforcement discretion to compounding six peptides. October 29, 2026. https://ncpa.org/newsroom/qam/2026/10/29/fda-grants-enforcement-discretion-compounding-six-peptides
6. Philp D et al. Thymosin beta 4 and a synthetic peptide containing its actin-binding domain promote dermal wound repair in db/db diabetic mice and in aged mice. Wound Repair Regen 2003. https://pubmed.ncbi.nlm.nih.gov/12581423/
7. Ho EN et al. Doping control analysis of TB-500, a synthetic version of an active region of thymosin beta4, in equine urine and plasma. J Chromatogr A 2012. https://pubmed.ncbi.nlm.nih.gov/23084823/
8. Ruff D et al. A randomized, placebo-controlled, single and multiple dose study of intravenous thymosin beta4 in healthy volunteers. Ann N Y Acad Sci 2010. https://pubmed.ncbi.nlm.nih.gov/20536472/
9. Treadwell T et al. The regenerative peptide thymosin beta4 accelerates the rate of dermal healing in preclinical animal models and in patients. Ann N Y Acad Sci 2012. https://pubmed.ncbi.nlm.nih.gov/23050815/