# TB-500 TB-500 is in limbo: it is not approved, and it is on neither FDA list for compounding, so no pharmacy may lawfully make it. The evidence grade is animal-only. No study has given it to people, so nobody knows if it helps or how safe it is. Status checked: 2026-10-25. Last verified: 2026-10-25. Primary source: https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks This page has not been individually reviewed by a clinician. Information, not medical advice. | Fact | Value | Tier | Checked | Source | |---|---|---|---|---| | Also called | TB500, TB-500 free base, TB-500 acetate, thymosin beta-4 fragment (LKKTETQ) | primary | 2026-10-25 | [source](https://www.fda.gov/media/193349/download) | | Class | healing-and-repair | primary | 2026-10-25 | [source](https://www.fda.gov/media/193349/download) | | Regulatory status | limbo | primary | 2026-10-25 | [source](https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks) | | Status source read | 2026-10-23 | primary | 2026-10-25 | [source](https://www.fda.gov/media/94155/download) | | Evidence grade | animal-only | our assessment | 2026-10-25 | [source](https://peptideindex.ai/methodology#evidence-grade) | ## Name TB-500 Source: https://www.fda.gov/media/193349/download ## Summary A lab-made chain of seven amino acids copied from a small part of a natural protein. It is in no FDA-approved drug. It is sold for injury recovery. Source: https://www.fda.gov/media/193349/download ## Short answer TB-500 is in limbo: it is not approved, and it is on neither FDA list for compounding, so no pharmacy may lawfully make it. The evidence grade is animal-only. No study has given it to people, so nobody knows if it helps or how safe it is. Source: https://peptideindex.ai/methodology#short-answer ## Known risks - FDA warns that a peptide shot like TB-500 may set off the immune system. Peptides can clump together, which can make this worse [^6]. - FDA says the name TB-500 is used for more than one substance. A product sold as TB-500 may not hold the form a doctor ordered [^6]. - A lab that tested TB-500 products sold online found their contents did not always match what they claimed to be [^17]. - FDA warns that shots made outside drug rules can carry germs or toxins straight into the blood. That can cause a life-threatening infection [^9]. Source: https://www.fda.gov/media/193349/download ## What nobody knows yet - No study has given TB-500 to people, so nobody knows if it helps any human illness or what harm it does [^6]. - No animal study has checked TB-500 for harm to organs, genes or unborn babies, or for cancer [^6]. - In one lab test on skin cells, TB-500 did not help a scratch close. Nobody knows if it heals wounds in a living body [^6]. - The body breaks TB-500 into smaller pieces. Nobody knows if TB-500 would act on its own or only through one of those pieces [^6]. Source: https://www.fda.gov/media/193349/download ## What it is TB-500 is a lab-made chain of seven amino acids [^6]. Amino acids are the building blocks of proteins. The chain copies a small part of thymosin beta-4, a protein the body makes, with one small chemical change at its start [^6] [^16]. Thymosin beta-4 has 43 amino acids, so TB-500 is a short piece of it [^6]. TB-500 and thymosin beta-4 are not the same substance, even though many websites use the names as if they were [^6]. TB-500 is part of no FDA-approved drug and has no official quality standard [^6]. Websites promote it for injury recovery, tendons, muscles, wounds, hair growth and many other uses [^6]. Sport testing labs look for it because athletes and racehorses may be given it [^6] [^16]. Source: https://www.fda.gov/media/193349/download ## Where it stands legally TB-500 is in limbo: FDA lists it among the Category 2 substances whose nominations were withdrawn, and it has not added it to Category 1 [^1] [^2]. That is not approval, and it does not make compounding lawful. FDA reviewed it as a shot for wound healing, but websites promote it for injury recovery, muscle and much more [^5] [^6]. Checked 23 October 2026. Category 2 is FDA's list of substances that may present significant safety risks. Category 1 is the list of substances pharmacies may use while FDA reviews them [^3]. The pharmacy that nominated TB-500 pulled its nomination, so it came off Category 2 [^1] [^6]. FDA then reviewed it on its own. FDA's scientists found no study of TB-500 in people and advised against adding it to the list [^6] [^8]. On 23 July 2026, FDA's Pharmacy Compounding Advisory Committee met on TB-500 [^4] [^5] [^7]. News and legal reports say it voted 8 to 6, with 1 member abstaining, to recommend adding TB-500 to the list [^11] [^12] [^21]. FDA's meeting page does not show the vote [^5]. A committee vote is only advice [^21]. FDA decides by writing a rule, after public comment [^12] [^22]. Until then, a pharmacy that makes TB-500 is outside federal law [^3] [^11]. Selling it for people to use is also illegal, even when the label says it is for research only [^9]. Source: https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks ## What the evidence shows The evidence grade is animal-only: FDA found no study of TB-500 in people [^6]. One rat study, published in July 2026, tested a substance it calls synthetic thymosin beta-4 (TB-500) [^14]. Its summary does not say whether that was the seven-amino-acid piece. Most other studies cited for TB-500 used a different molecule. They are named below as borrowed evidence. The rat study: in rats whose Achilles tendon was cut and repaired, shots into the belly cavity gave stronger, more orderly tendons after four weeks [^14]. The authors call this an early result that needs more study [^14]. In a lab test on skin cells, TB-500 itself did not help a scratch close [^6]. Borrowed evidence: a 2003 mouse study tested thymosin beta-4 and a seven-amino-acid piece of it on skin wounds, and both sped healing [^15]. That piece lacks TB-500's chemical change, so FDA says its results do not carry over to TB-500 [^6]. A review reports that full-length thymosin beta-4 sped healing in animals and in two trials in people with skin ulcers [^18]. In 9 people with severe dry eye, thymosin beta-4 eye drops eased symptoms [^19]. In healthy volunteers, thymosin beta-4 given into a vein caused only mild or moderate problems [^20]. The last three used the whole protein, not TB-500. None of these results is evidence for TB-500 [^6]. Source: https://www.fda.gov/media/193349/download ## Legitimate ways to get it There is no legal way to get TB-500 in the US today [^6]. No approved drug contains it, here or in ten other countries FDA checked [^6]. A pharmacy may use a substance with no official quality standard only if it is in an approved drug or on the federal list. TB-500 is neither [^3] [^6]. That could change if FDA adds it by writing a rule after the committee vote [^11] [^12]. FDA found no clinical study of TB-500 in people [^6]. Trials of full-length thymosin beta-4 test a different molecule, so they are not listed here. Any open TB-500 trial would appear in the trials block below, with the date the official registry was last checked. Source: https://www.fda.gov/media/193349/download ## How people are getting it anyway This section describes what happens and is not a recommendation. People who use TB-500 get it in three main ways [^6] [^9]. The first is online sellers that label it for research use only. FDA has warned a seller of TB-500 that this label does not make it legal to sell a drug meant for people [^9] [^13]. The second is pharmacies. Two websites say they get TB-500 from a compounding pharmacy, though FDA found no pharmacy that markets it [^6]. The third is websites where people book an online visit to discuss using it [^6]. In all three, nobody checks what is in the product the way FDA checks an approved drug. A lab found that TB-500 products bought online did not always hold what they claimed [^17]. FDA found two reports of problems with a TB-500 and BPC-157 blend, with no assessment of harm [^6]. FDA does not get every report of harm, especially for compounded products, so these files cannot show how often harm happens [^6]. Source: https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/warrior-labz-sarms-655280-06122023 ## Access routes Source: https://www.fda.gov/media/193349/download ### None Detail: There is no legal route to TB-500 in the US today. It is in no approved drug, has no official quality standard, and is not on the list pharmacies may use. Source: https://www.fda.gov/media/193349/download ## Unofficial channels Source: https://www.fda.gov/media/193349/download ### Research use seller What it is: Sold online in vials with a label saying it is for research use only and not for people. Legal position: FDA treats these products as unapproved new drugs when the seller's claims show they are meant for people, whatever the label says. (source: https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/warrior-labz-sarms-655280-06122023) Documented risks: - FDA warns that injected drugs bypass the body's defenses and can carry toxins or germs that cause sepsis. (source: https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/warrior-labz-sarms-655280-06122023) - A lab that tested TB-500 products sold online found their contents did not always match their descriptions. (source: https://pubmed.ncbi.nlm.nih.gov/36482504/) Enforcement: - 2023-06-12: FDA warning letter to an online seller that listed TB-500 among its unapproved new drugs. (source: https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/warrior-labz-sarms-655280-06122023) - 2026-08-24: FDA warning letter to an online seller of research-use peptide shots. The letter did not name TB-500. (source: https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/peptide-partners-llc-735063-08242026) Source: https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/warrior-labz-sarms-655280-06122023 ### Compounding outside the rules What it is: Made by a pharmacy from bulk TB-500 powder. Two websites say their TB-500 comes from a compounding pharmacy. Legal position: TB-500 has no official quality standard, is in no approved drug and is not on the federal list, so a pharmacy may not compound it under section 503A. (source: https://www.fda.gov/drugs/human-drug-compounding/bulk-drug-substances-used-compounding-under-section-503a-fdc-act) Documented risks: - FDA found no study of TB-500 in people by any route, so the safety of a compounded product is unknown. (source: https://www.fda.gov/media/193349/download) - FDA found that the public test sheets for TB-500 powder skip key checks, such as for clumps and germ toxins. (source: https://www.fda.gov/media/193349/download) Source: https://www.fda.gov/drugs/human-drug-compounding/bulk-drug-substances-used-compounding-under-section-503a-fdc-act ### Telehealth What it is: Websites where a person can book a visit to discuss using TB-500. They do not say how the TB-500 is obtained. Legal position: A prescription does not make TB-500 lawful to compound. It is still a substance that is not on the federal list. (source: https://www.fda.gov/drugs/human-drug-compounding/bulk-drug-substances-used-compounding-under-section-503a-fdc-act) Documented risks: - FDA found no human data on any product with TB-500, including whether it sets off the immune system. (source: https://www.fda.gov/media/193349/download) Source: https://www.fda.gov/drugs/human-drug-compounding/bulk-drug-substances-used-compounding-under-section-503a-fdc-act ## Recruiting trials Snapshot date: 2026-10-25. A listing is not a recommendation. Trials have strict eligibility rules. Talk to your doctor and read the official record. None in this snapshot. Source: https://clinicaltrials.gov/api/v2/studies?query.intr=Ac-LKKTETQ+OR+LKKTETQ&filter.overallStatus=RECRUITING%2CNOT_YET_RECRUITING&pageSize=50&sort=StartDate%3Adesc&countTotal=true&fields=NCTId%2CBriefTitle%2COverallStatus%2CPhase%2CLeadSponsorName%2CStartDate%2CLocationCountry%2CLocationState ## Sources Source: https://www.fda.gov/media/193349/download ### 1. FDA: bulk drug substances that may present significant safety risks, including those withdrawn from Category 2 Type: regulatory Tier: primary Source: https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks ### 2. FDA: bulk drug substances nominated under section 503A, list updated 14 May 2026 Type: regulatory Tier: primary Source: https://www.fda.gov/media/94155/download ### 3. FDA: bulk drug substances used in compounding under section 503A Type: regulatory Tier: primary Source: https://www.fda.gov/drugs/human-drug-compounding/bulk-drug-substances-used-compounding-under-section-503a-fdc-act ### 4. Federal Register: notice of the July 2026 Pharmacy Compounding Advisory Committee meeting Type: regulatory Tier: primary Source: https://www.federalregister.gov/documents/full_text/html/2026/04/16/2026-07361.html ### 5. FDA: Pharmacy Compounding Advisory Committee meeting, 23 and 24 July 2026 Type: regulatory Tier: primary Source: https://www.fda.gov/advisory-committees/advisory-committee-calendar/july-23-24-2026-meeting-pharmacy-compounding-advisory-committee-07232026 ### 6. FDA briefing document on TB-500 for the July 2026 committee meeting, 15 May 2026 Type: regulatory Tier: primary Source: https://www.fda.gov/media/193349/download ### 7. FDA: questions put to the committee at the July 2026 meeting Type: regulatory Tier: primary Source: https://www.fda.gov/media/193711/download ### 8. FDA: presentations to the committee on 23 July 2026, including TB-500 Type: regulatory Tier: primary Source: https://www.fda.gov/media/193773/download ### 9. FDA warning letter to an online seller that listed TB-500, 12 June 2023 Type: regulatory Tier: primary Source: https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/warrior-labz-sarms-655280-06122023 ### 10. FDA warning letter to an online seller of research-use peptides, 24 August 2026 Type: regulatory Tier: primary Source: https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/peptide-partners-llc-735063-08242026 ### 11. McDermott Will & Schulte: what the July 2026 committee votes on peptides mean Type: legal-analysis Tier: legal-analysis Source: https://www.mcdermottlaw.com/insights/bulk-list-bound-pcac-backs-majority-of-peptides-in-two-day-public-meeting/ ### 12. FDA Law Blog: the committee recommends four peptides for the 503A list Type: legal-analysis Tier: legal-analysis Source: https://www.thefdalawblog.com/2026/07/peptide-l-wave-pcac-approves-four-bulk-drug-substances-for-the-503a-list/ ### 13. Sheppard Mullin: FDA's peptide policy and its warning letters to peptide sellers Type: legal-analysis Tier: legal-analysis Source: https://www.sheppard.com/insights/blogs/fda-balances-peptide-policy-with-enforcement-against-unlawful-peptide-sellers ### 14. TB-500 and BPC-157 on Achilles tendon healing in rats, 2026 Type: animal Tier: peer-reviewed Source: https://pubmed.ncbi.nlm.nih.gov/42542926/ ### 15. Thymosin beta-4 and a seven-amino-acid piece of it on skin wounds in diabetic and aged mice, 2003 Type: animal Tier: peer-reviewed Source: https://pubmed.ncbi.nlm.nih.gov/12581423/ ### 16. Identifying the thymosin beta-4 fragment in TB-500 for sport testing, 2012 Type: in-vitro Tier: peer-reviewed Source: https://pubmed.ncbi.nlm.nih.gov/22962027/ ### 17. Lab analysis of mislabeled and impure TB500 products sold online, 2023 Type: in-vitro Tier: peer-reviewed Source: https://pubmed.ncbi.nlm.nih.gov/36482504/ ### 18. Review: full-length thymosin beta-4 and skin healing in animals and patients, 2012 Type: reference Tier: peer-reviewed Source: https://pubmed.ncbi.nlm.nih.gov/23050815/ ### 19. Thymosin beta-4 eye drops for severe dry eye: a small randomized trial, 2015 Type: rct Tier: peer-reviewed Source: https://pubmed.ncbi.nlm.nih.gov/25826322/ ### 20. First test of full-length thymosin beta-4 in healthy volunteers, 2021 Type: human-trial Tier: peer-reviewed Source: https://pubmed.ncbi.nlm.nih.gov/34346165/ ### 21. NBC News: FDA panel recommends easing peptide limits despite agency scientists Type: reference Tier: established-news Source: https://www.nbcnews.com/health/health-news/peptides-restrictions-ease-fda-panel-recommend-bpc-157-scientists-rcna588879 ### 22. NPR: FDA advisers back easing limits on six peptides, 23 July 2026 Type: reference Tier: established-news Source: https://www.npr.org/2026/07/23/nx-s1-5903202/fda-peptides-restrictions Last verified: 2026-10-25. Sources: - https://clinicaltrials.gov/api/v2/studies?query.intr=Ac-LKKTETQ+OR+LKKTETQ&filter.overallStatus=RECRUITING%2CNOT_YET_RECRUITING&pageSize=50&sort=StartDate%3Adesc&countTotal=true&fields=NCTId%2CBriefTitle%2COverallStatus%2CPhase%2CLeadSponsorName%2CStartDate%2CLocationCountry%2CLocationState - https://peptideindex.ai/methodology#evidence-grade - https://peptideindex.ai/methodology#short-answer - https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks - https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/warrior-labz-sarms-655280-06122023 - https://www.fda.gov/media/193349/download - https://www.fda.gov/media/94155/download [^1]: FDA: bulk drug substances that may present significant safety risks, including those withdrawn from Category 2 https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks [^2]: FDA: bulk drug substances nominated under section 503A, list updated 14 May 2026 https://www.fda.gov/media/94155/download [^3]: FDA: bulk drug substances used in compounding under section 503A https://www.fda.gov/drugs/human-drug-compounding/bulk-drug-substances-used-compounding-under-section-503a-fdc-act [^4]: Federal Register: notice of the July 2026 Pharmacy Compounding Advisory Committee meeting https://www.federalregister.gov/documents/full_text/html/2026/04/16/2026-07361.html [^5]: FDA: Pharmacy Compounding Advisory Committee meeting, 23 and 24 July 2026 https://www.fda.gov/advisory-committees/advisory-committee-calendar/july-23-24-2026-meeting-pharmacy-compounding-advisory-committee-07232026 [^6]: FDA briefing document on TB-500 for the July 2026 committee meeting, 15 May 2026 https://www.fda.gov/media/193349/download [^7]: FDA: questions put to the committee at the July 2026 meeting https://www.fda.gov/media/193711/download [^8]: FDA: presentations to the committee on 23 July 2026, including TB-500 https://www.fda.gov/media/193773/download [^9]: FDA warning letter to an online seller that listed TB-500, 12 June 2023 https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/warrior-labz-sarms-655280-06122023 [^11]: McDermott Will & Schulte: what the July 2026 committee votes on peptides mean https://www.mcdermottlaw.com/insights/bulk-list-bound-pcac-backs-majority-of-peptides-in-two-day-public-meeting/ [^12]: FDA Law Blog: the committee recommends four peptides for the 503A list https://www.thefdalawblog.com/2026/07/peptide-l-wave-pcac-approves-four-bulk-drug-substances-for-the-503a-list/ [^13]: Sheppard Mullin: FDA's peptide policy and its warning letters to peptide sellers https://www.sheppard.com/insights/blogs/fda-balances-peptide-policy-with-enforcement-against-unlawful-peptide-sellers [^14]: TB-500 and BPC-157 on Achilles tendon healing in rats, 2026 https://pubmed.ncbi.nlm.nih.gov/42542926/ [^15]: Thymosin beta-4 and a seven-amino-acid piece of it on skin wounds in diabetic and aged mice, 2003 https://pubmed.ncbi.nlm.nih.gov/12581423/ [^16]: Identifying the thymosin beta-4 fragment in TB-500 for sport testing, 2012 https://pubmed.ncbi.nlm.nih.gov/22962027/ [^17]: Lab analysis of mislabeled and impure TB500 products sold online, 2023 https://pubmed.ncbi.nlm.nih.gov/36482504/ [^18]: Review: full-length thymosin beta-4 and skin healing in animals and patients, 2012 https://pubmed.ncbi.nlm.nih.gov/23050815/ [^19]: Thymosin beta-4 eye drops for severe dry eye: a small randomized trial, 2015 https://pubmed.ncbi.nlm.nih.gov/25826322/ [^20]: First test of full-length thymosin beta-4 in healthy volunteers, 2021 https://pubmed.ncbi.nlm.nih.gov/34346165/ [^21]: NBC News: FDA panel recommends easing peptide limits despite agency scientists https://www.nbcnews.com/health/health-news/peptides-restrictions-ease-fda-panel-recommend-bpc-157-scientists-rcna588879 [^22]: NPR: FDA advisers back easing limits on six peptides, 23 July 2026 https://www.npr.org/2026/07/23/nx-s1-5903202/fda-peptides-restrictions