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TB-500 in 2026: FDA status, legal access, dosage and side effects

What changed with HHS’s October 2026 policy, what TB-500 is (and is not), and why there are no human data on it.

TB-500 is a synthetic peptide built around a seven-amino-acid fragment (Ac-LKKTETQ) of thymosin beta-4, the region that binds actin inside cells. FDA has identified no human exposure data for it. It is not FDA-approved; since October 2026, a 503A pharmacy may compound it on a patient-specific prescription under listed conditions. REMEVi does not offer TB-500.

TB-500 is not FDA-approved. Since HHS’s October 2026 interim policy, a state-licensed 503A pharmacy may compound it on a patient-specific prescription under listed conditions.

REMEVi does not currently offer TB-500.

What changed in 2026

On October 30, 2026, the Federal Register published notice of HHS’s interim enforcement-discretion policy for 503A compounding. In plain words: HHS says it does not intend to take enforcement action against a state-licensed 503A pharmacy or federal facility that compounds TB-500 for an individual patient, as long as every listed condition is met.

For TB-500 the policy lists two routes: subcutaneous or intramuscular injection. All of these conditions apply together:

  • A patient-specific prescription from a licensed prescriber.
  • Compounding by a state-licensed 503A pharmacy (or a federal facility).
  • TB-500 used by a route listed in the policy’s appendix: subcutaneous or intramuscular injection.
  • Bulk TB-500 from an FDA-registered facility with a valid certificate of analysis (CoA); the original manufacturer FDA-registered and CGMP-compliant.
  • One active ingredient per product. A premixed TB-500 + BPC-157 product does not qualify.
  • The one device packaged with the drug is an FDA 510(k)-cleared syringe.
  • The label reads “This is a compounded drug product. Not for resale.”
  • Serious adverse events reported to FDA MedWatch.

The policy is interim, non-binding and revocable. It is not FDA approval and does not add TB-500 to the 503A bulks list; FDA may propose that later through rulemaking. HHS says it may revisit the policy if a safety signal or product quality issue arises. It covers 503A compounding, not 503B outsourcing facilities. Public comments were open for two weeks after publication (docket HHS-OASH-2026-0496).

Federal Register notice (Oct 30, 2026) · The 2026 policy, explained for patients

How a lawful TB-500 prescription works

  1. A licensed prescriber evaluates you: history, medications, and whether TB-500 is appropriate for you at all.
  2. If they decide to prescribe, they write a patient-specific prescription for subcutaneous or intramuscular use.
  3. A state-licensed 503A pharmacy compounds it from documented bulk substance (FDA-registered source, valid CoA), with TB-500 as the single active ingredient.
  4. The product is dispensed to you, labelled “This is a compounded drug product. Not for resale.”
  5. Any serious adverse event is reported to FDA MedWatch.

A prescription is a clinical decision, not a formality. Given how little is known about TB-500 in people, a provider may decide it is not right for you.

Research-grade vials vs compounded prescriptions

Vials sold online labelled for research use are not compounded prescriptions, and the 2026 policy does not cover them. There is no prescriber, no patient-specific label, no licensed pharmacy answerable for what is in the vial, and no adverse-event reporting. Many are sold premixed with other peptides, which the policy would not cover either.

On August 24, 2026, FDA sent warning letters to five online peptide vendors. According to Holland & Knight’s summary, research-use labels did not outweigh evidence that the products were meant for people.

What research exists on TB-500: almost none in people

FDA says it has not identified any human exposure data for products containing the thymosin beta-4 fragment sold as TB-500. Most of what is written about TB-500 borrows from research on full-length thymosin beta-4, a different, larger molecule.

  • TB-500 itself: published work is mainly doping-control chemistry. A 2012 study identified its active content as the acetylated LKKTETQ fragment and detected it in two horses after a single injection.
  • Full-length thymosin beta-4, human: a 2010 phase 1 trial gave intravenous thymosin beta-4 to 40 healthy volunteers (randomized, placebo-controlled). It measured tolerability and blood levels, not any treatment outcome, and it was not TB-500.
  • Full-length thymosin beta-4, animal: a 2010 review describes animal models of skin, cornea and heart injury, where thymosin beta-4 was studied for cell migration and blood-vessel growth.

Research on thymosin beta-4 does not show what TB-500 does in people. No human trial has established that TB-500 treats any condition.

TB-500 side effects: what is known

There are no human side-effect data on TB-500. FDA flags possible immunogenicity from aggregation and peptide-related impurities, and says it lacks information on whether TB-500 would cause harm in humans. Injection-site reactions are possible with any injection.

TB-500 side effects: human, animal and unknown

TB-500 dosage: no established human dose

No human dose of TB-500 has been established by either listed route. Published protocols vary; a licensed provider sets your dose; never self-dose.

TB-500 dosage: what has been published

TB-500 cost

Very few programs publish a price for compounded TB-500. REMEVi does not currently price TB-500.

TB-500 cost: prescription vs research-grade

Is TB-500 FDA approved?

No. TB-500 is not FDA-approved for any use, and FDA says it has not identified human exposure data for it. The 2026 HHS policy is enforcement discretion for compounding, not approval: HHS says it does not grant FDA approval or establish clinical safety and effectiveness for the six listed peptides.

Is TB-500 the same as thymosin beta-4?

No. Thymosin beta-4 is a naturally occurring actin-binding peptide. TB-500 is a synthetic peptide whose active content was identified as a seven-amino-acid fragment of it (Ac-LKKTETQ), the actin-binding region. Human trials of full-length thymosin beta-4 are not trials of TB-500, and the results do not transfer.

What is TB-500 used for?

TB-500 has no established medical use. FDA has identified no human exposure data for it. Its parent protein, thymosin beta-4, has been studied in animal models of skin, cornea and heart injury, and in early human trials of the full-length protein. None of that shows what TB-500 does in people.

Sources

  1. HHS — Enforcement Discretion Policy Regarding 503A Compounding Using Certain Peptide Bulk Drug Substances, notice of availability, 91 FR 68526 (October 30, 2026) (read November 2, 2026)
  2. Foley & Lardner (Holtz, Beaver, Rosen), National Law Review, Oct 30 2026 — Peptides: HHS announces limited enforcement discretion for compounding six peptides (read November 2, 2026)
  3. Nutritional Outlook (Bigica), Nov 2 2026 — HHS peptide compounding policy: supplement industry implications (read November 2, 2026)
  4. AJMC (Steinzor), Oct 29 2026 — 5 things to know about HHS’s interim peptide compounding policy (read November 2, 2026)
  5. Holland & Knight, Oct 16 2026 — Peptides at a crossroads: what wellness providers need to know (read November 2, 2026)
  6. FDA — Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks (content current as of 04/22/2026) (read November 2, 2026)
  7. Ho et al., J Chromatogr A 2012 — Doping control analysis of TB-500, a synthetic version of an active region of thymosin β4, in equine urine and plasma by LC-MS (read November 2, 2026)
  8. Ruff et al., Ann N Y Acad Sci 2010 — A randomized, placebo-controlled, single and multiple dose study of intravenous thymosin beta4 in healthy volunteers (read November 2, 2026)
  9. Philp & Kleinman, Ann N Y Acad Sci 2010 — Animal studies with thymosin beta-4 (review) (read November 2, 2026)

Medically reviewed by Linda West-Conforti, RN · CA RN #389453 ·