TB-500: what it is, prescription status and cost

TB-500 is a lab-made seven-amino-acid fragment of thymosin beta-4, a protein the body makes. It has no FDA approval, but since 28 October 2026 HHS says it will not act against licensed 503A pharmacies that compound it under set conditions (Federal Register). Prescription programs start at $149 a month; see every TB-500 price.

Compounded drugs are not FDA-approved, and the HHS policy is interim and can be withdrawn. Status checked on 30 October 2026.

What TB-500 is, and how it differs from thymosin beta-4

Thymosin beta-4 is a naturally occurring 43-amino-acid protein (Guarnera 2010). Researchers have tested a synthetic copy of the full protein in people for slow-healing wounds and eye disease, and studied it for heart attacks. TB-500 is something narrower: a short piece of that protein.

When a Belgian anti-doping laboratory analysed a product sold as TB-500, it identified "the N-terminal acetylated 17-23 fragment of human thymosin beta 4 (Ac-LKKTETQ) in TB-500" (Esposito 2012, PubMed 22962027). HHS uses the same identity in its policy: its sequence is "Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln-OH" (HHS policy, Appendix B).

The two names are often used as if they were the same drug. A 2026 orthopaedic review warns that "TB-500 is a distinct seven amino-acid fragment of TB-4 that is frequently conflated with full-length TB-4 despite the absence of validated biologic or clinical equivalence" (Tham 2026, PubMed 42937313). That matters for everything below: the human trials were run with the full protein, not with TB-500.

What human evidence exists

For TB-500 itself, very little. FDA's own entry for the fragment says: "FDA has not identified any human exposure data drug products containing Thymosin Beta-4, Fragment" (FDA). We searched PubMed and ClinicalTrials.gov on 30 October 2026 and found no published controlled trial of the fragment in people. One registry entry titled as a TB-500 trial, NCT07487363, describes itself this way: "This fictional study is an example of a ClinicalTrials.gov-style record" (ClinicalTrials.gov record). Treat it as no evidence.

The full protein has a longer record, much of it sponsored by RegeneRx and its partner ReGenTree:

In the venous ulcer trial the authors wrote that "The safety profile of all doses of administered Tbeta4 was deemed acceptable and comparable to placebo" (Guarnera 2010). In the dry eye Phase 2, "Neither of the primary endpoints, ie, ocular discomfort or inferior corneal staining, showed a significant difference between treatment and control groups at visit 5" (Sosne 2015).

None of this tested injected TB-500 for muscle, tendon or joint recovery, which is how it is marketed. The Tham review concluded that for these peptides "Routine clinical use cannot be currently recommended" (Tham 2026). Preclinical studies on tissue repair exist, but preclinical results often fail to carry over to people.

FDA and HHS status in October 2026

FDA placed the fragment in its "category 2" group of bulk substances that may present significant safety risks. HHS records that "TB-500 was in Category 2 from September 29, 2023, until April 22, 2026", when it left the list because its nomination was withdrawn (HHS policy). FDA's stated concern was that TB-500 "may pose risk for immunogenicity for certain routes of administration due to the potential for aggregation as well as peptide-related impurities" (FDA).

On 28 October 2026 the HHS Secretary signed an interim enforcement-discretion policy covering six peptides, TB-500 among them. HHS states that it "does not intend to take enforcement action against a State-licensed pharmacy, Federal facility, or licensed physician compounding a drug product using a peptide bulk drug substance found in Appendix A" (Federal Register). For TB-500 the policy names injection under the skin or into muscle only: "subcutaneous or intramuscular injectable dosage forms" (HHS policy).

Key limits, from the policy text:

• Single ingredient only. "The compounded drug product contains only a single Active Pharmaceutical Ingredient (API) listed in Appendix A" (HHS policy). Blends with BPC-157 are outside it; see BPC-157 vs TB-500.
• Patient-specific prescription. A licensed clinician has to prescribe for you.
• Traceable ingredient. The raw peptide must come from an FDA-registered manufacturer with a lot-specific certificate of analysis.
• It can change. "HHS may revisit application of this interim policy (in whole or in part) if, among other things, a safety signal or product quality issue arises" (Federal Register).

The notice also says the policy "does not establish any rights for any person and is not binding on HHS or the public", and that "Compounded drugs are not FDA-approved, which means FDA does not review their safety, effectiveness, or quality before they are marketed" (Federal Register). Our HHS peptide policy guide covers the full text, and peptide legal status tracks all six.

WADA: banned in tested sport

The World Anti-Doping Agency lists TB-500 by name. Under its growth factors class (S2.3), the 2026 Prohibited List includes "Thymosin-ß4 and its derivatives e.g. TB-500", in a section marked "PROHIBITED AT ALL TIMES (IN- AND OUT-OF-COMPETITION)" (WADA 2026 Prohibited List). A prescription does not change that. Athletes subject to testing would need a Therapeutic Use Exemption from their anti-doping organisation. WADA notes that "The Prohibited List comes into effect on January 1st of each year" (WADA), so check the current list before any season.

Programs and price

One prescription program in our table offers TB-500 as of 30 October 2026. Superpower opened preorders after the HHS policy, with a target ship date in late November. Its page says "The initial BPC-157, TB-500 and MOTS-c products are not FDA-approved" (Superpower).

First month is charged at preorder, with a full refund if a clinician does not approve the prescription. See the Superpower review and the TB-500 price page, which updates as programs add the peptide. We do not list research-use-only sellers; research vs prescription peptides explains why.

Your prescriber decides whether TB-500 suits you and how it is used. We do not publish doses. Safety detail is in TB-500 side effects.

FAQ

TB-500: what is it, and is it available by prescription?

TB-500 is a synthetic seven-amino-acid fragment of thymosin beta-4. Since the 28 October 2026 HHS interim policy, licensed 503A pharmacies may compound it as a single-ingredient injection on a patient-specific prescription without HHS enforcement action. Compounded TB-500 is not FDA-approved, the policy can be withdrawn, and availability depends on the program and your state.

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

No. Thymosin beta-4 is the full 43-amino-acid protein. TB-500 is a seven-amino-acid piece of it, the acetylated 17-23 region. Human trials used the full protein in eye drops, skin gels and intravenous infusions. No published controlled trial tested TB-500 itself, so results from thymosin beta-4 studies cannot be assumed to apply.

What is the TB 500 peptide used for?

Marketing pitches TB-500 for muscle, tendon and injury recovery. Those uses rest on preclinical work, not human trials. Thymosin beta-4, the parent protein, was tested in people for dry eye, a corneal disease and slow-healing skin ulcers, with mixed results. A 2026 orthopaedic review said routine clinical use cannot currently be recommended.

Is TB-500 FDA approved?

No. FDA has not approved TB-500 or thymosin beta-4 for any use. The HHS policy is an enforcement statement, not an approval: HHS says it will not act against compliant 503A compounding while FDA works on rulemaking. Compounded drugs are not reviewed by FDA for safety, effectiveness or quality before sale.

Is TB-500 banned in sports?

Yes. WADA's 2026 Prohibited List names "Thymosin-ß4 and its derivatives e.g. TB-500" under growth factors, prohibited in and out of competition. A valid prescription does not make it permitted for tested athletes. Anyone in tested sport should ask their anti-doping organisation about a Therapeutic Use Exemption before starting.

How much does TB-500 cost with a prescription?

Prescription TB-500 starts at $149 a month at Superpower, the one program in our table offering it on 30 October 2026. That price includes the clinician review, a blood test and membership. Prices change as programs launch, so check the live TB-500 cost page.

Compare every prescription peptide program on price, pharmacy and oversight on the best peptide programs page.