TB-500 (thymosin beta-4) regulatory status
Current status of TB-500 (thymosin beta-4) in the United States: Under FDA review. In sport: WADA prohibited. Details, sources, and the dated timeline follow.
By the PeptideAgent Editorial Team. Draft, pending editorial review. Last verified
What is the current status of TB-500 (thymosin beta-4)?
- FDA and compounding
- Removed from the FDA 503A Category 2 list (substances nominated for compounding that raise significant safety risks) on April 15, 2026. On July 23 to 24, 2026 the Pharmacy Compounding Advisory Committee recommended adding TB-500 to the 503A bulks list. As of the last verification date FDA has not published a final rule listing it, so it is not on the 503A bulks list and a 503A pharmacy has no federal basis to compound it from bulk; state boards cannot authorize what federal law does not. It is not an FDA approved drug and is not eligible for 503B outsourcing. Products sold as research chemicals are not lawful for human use.
- WADA
- WADA prohibited
- Access path
- No lawful compounded access path yet: PCAC recommended it for the 503A bulks list in July 2026, but until FDA publishes a final rule a 503A pharmacy has no federal basis to compound it from bulk.
- Not available as an FDA approved product.
- Products labeled research use only are not lawful for human use and are not verified for purity.
Full TB-500 (thymosin beta-4) page: evidence, dosing in the literature, and sources
Is TB-500 (thymosin beta-4) FDA approved or legal? Questions and answers
Is TB-500 FDA approved?
No. TB-500 is not an FDA approved drug for any use. FDA removed it from the 503A Category 2 list on April 15, 2026, and the Pharmacy Compounding Advisory Committee recommended it for the 503A bulks list on July 23 to 24, 2026. That recommendation is advisory: it is not an approval, and FDA must still publish a final rule before a 503A pharmacy may compound it. [1] [2] [3]
What is the FDA status of TB-500 in 2026?
Under FDA review. TB-500 is off the 503A Category 2 list and has a positive advisory committee vote, but as of September 2026 FDA has not published a final rule adding it to the 503A bulks list. Until it does, a 503A pharmacy has no federal basis to compound it from bulk, and it is not eligible for 503B outsourcing. [2] [3]
Is TB-500 legal?
There is no lawful way to obtain TB-500 for human use in the United States today. It is not an approved drug, it is not yet on the 503A bulks list, and state boards cannot authorize compounding that federal law does not allow. Products sold as research chemicals are not lawful for human use and are not verified for purity. [2] [3]
Is TB-500 banned by WADA?
Yes. The WADA Prohibited List names thymosin beta-4 and its derivatives, including TB-500, under section S2 (peptide hormones, growth factors, related substances and mimetics). It is prohibited at all times, in and out of competition. [4]
How has the status of TB-500 (thymosin beta-4) changed over time?
- WADA
WADA publishes the 2027 Prohibited List
WADA published the 2027 Prohibited List on September 21, 2026, and it takes effect January 1, 2027. The S2 peptide hormone and growth factor classes are unchanged. BPC-157 is still named under S0, and MOTS-c is still named under S4.4 as an activator of AMP-activated protein kinase. WADA added a note that many peptides without approval for human use fall under S0 or another section, and that a peptide not named on the list may still be prohibited. GLP-1 receptor agonists such as semaglutide and tirzepatide are still not on the list.
- PCAC
PCAC recommends six peptides for the 503A bulks list
At its July 23 to 24, 2026 meeting, FDA's Pharmacy Compounding Advisory Committee voted to recommend that BPC-157, KPV, TB-500, MOTS-c, semax, and epitalon be added to the 503A bulk drug substances list. A committee recommendation is advisory; FDA must still issue a rule before the substances are formally listed.
Regulatory: Under FDA reviewSource: Pharmacy Compounding Advisory Committee - FDA
FDA lists BPC-157 and 16 other peptides as withdrawn from 503A Category 2
FDA's Category 2 page, revised in April 2026 and current as of April 22, 2026, moved BPC-157, AOD-9604, CJC-1295, dihexa, DSIP, epitalon, injectable GHK-Cu, ipamorelin, KPV, LL-37, melanotan II, MOTS-c, PEG-MGF, selank, semax, thymosin alpha-1, and thymosin beta-4 fragment (TB-500) to a list of bulk drug substances nominated but withdrawn by their nominators. A withdrawn substance is no longer in 503A Category 2, but withdrawal is not an approval and does not place a substance on the 503A bulks list; a 503A pharmacy still needs a listing before it may compound it. Ipamorelin acetate remains in 503B Category 2. Seven of the withdrawn peptides (BPC-157, KPV, TB-500, MOTS-c, semax, epitalon, and DSIP) were taken to the Pharmacy Compounding Advisory Committee in July 2026.
- WADA
WADA 2026 Prohibited List takes effect
The 2026 WADA Prohibited List took effect on January 1, 2026 and continues to prohibit the S2 peptide hormone and growth factor classes (GHRH analogs, growth hormone secretagogues, GH fragments, IGF-1 and analogs, MGF, thymosin beta-4 and derivatives, hCG and GnRH-class releasing factors in males), myostatin inhibitors, insulin and the AMPK activator MOTS-c under S4, desmopressin under S5, and BPC-157 under S0. GLP-1 receptor agonists such as semaglutide and tirzepatide are not on the list.
- WADA
WADA 2025 Prohibited List keeps peptide hormones and growth factors banned at all times
The 2025 WADA Prohibited List took effect on January 1, 2025. Section S2 (peptide hormones, growth factors, related substances and mimetics) covers GHRH analogs such as CJC-1295, sermorelin, and tesamorelin, growth hormone secretagogues such as ipamorelin, GHRP-2, GHRP-6, hexarelin, and ibutamoren (MK-677), growth hormone fragments such as AOD-9604, growth factors including IGF-1 and its analogs, MGF, and thymosin beta-4 (TB-500), and chorionic gonadotropin and releasing factors such as gonadorelin and kisspeptin (prohibited in males). Myostatin inhibitors such as ACE-031 fall under S4, insulin under S4 metabolic modulators, desmopressin under S5, and BPC-157 remains an S0 non-approved substance.
- FDA
FDA places a batch of nominated peptides in 503A Category 2
In September 2023 FDA updated its 503A bulk drug substances category lists to place a group of nominated peptides in Category 2, which means FDA identified significant safety risks and the substances may not be used in 503A compounding while the evaluation continues. Kisspeptin-10 and ibutamoren (MK-677) were added on September 29, 2023 and remain in Category 2 on the FDA page current as of April 22, 2026. BPC-157, CJC-1295, ipamorelin, AOD-9604, dihexa, DSIP, epitalon, KPV, MOTS-c, selank, semax, melanotan II, LL-37, thymosin alpha-1, and thymosin beta-4 fragment (TB-500) were also placed in Category 2 under the 503A interim policy; that same page now lists them as nominated but withdrawn (see the April 2026 event). Hexarelin, PNC-27, and 5-amino-1MQ have never appeared on the FDA category lists.
Sources
Numbered citations in the answers above point here, followed by the regulatory sources on record for TB-500 (thymosin beta-4) and the source of each dated event.
- [1]FDA: Certain bulk drug substances for use in compounding that may present significant safety risks (503A Category 2 list and nominated but withdrawn substances, current as of April 22, 2026)FDA, 2026
- [2]FDA Pharmacy Compounding Advisory Committee meetings (July 2026 meeting on peptide nominations)FDA, 2026
- [3]FDA: Bulk drug substances used in compounding under section 503A of the FD&C Act (links to the Category 1, 2, and 3 lists and the bulks list)FDA, 2026
- [4]WADA Prohibited List, section S2 peptide hormones, growth factors, related substances and mimetics (names thymosin beta-4 and TB-500)WADA, 2026
- [5]WADA 2027 Prohibited ListWADA, 2026
From the blog
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