# Thymalin Thymalin has no approved use in the US. FDA calls Thymalin products sold online unapproved new drugs. It is a mix of peptides from the thymus gland. The evidence grade is limited-human: studies in Russia and Ukraine report gains, but most are small or old. Status checked: 2026-10-26. Last verified: 2026-10-26. Primary source: https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/us-chem-labs-669074-02072024 This page has not been individually reviewed by a clinician. Information, not medical advice. | Fact | Value | Tier | Checked | Source | |---|---|---|---|---| | Also called | Timalin | peer-reviewed | 2026-10-26 | [source](https://pubmed.ncbi.nlm.nih.gov/24003726/) | | Class | other | peer-reviewed | 2026-10-26 | [source](https://pubmed.ncbi.nlm.nih.gov/33237528/) | | Regulatory status | no-approved-use | primary | 2026-10-26 | [source](https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/us-chem-labs-669074-02072024) | | Status source read | 2026-10-26 | primary | 2026-10-26 | [source](https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/us-chem-labs-669074-02072024) | | Evidence grade | limited-human | our assessment | 2026-10-26 | [source](https://peptideindex.ai/methodology#evidence-grade) | ## Name Thymalin Source: https://pubmed.ncbi.nlm.nih.gov/33237528/ ## Summary A mix of peptides taken from the thymus gland, not one peptide. Researchers who study it say it helps regulate the immune system. Source: https://pubmed.ncbi.nlm.nih.gov/33237528/ ## Short answer Thymalin has no approved use in the US. FDA calls Thymalin products sold online unapproved new drugs. It is a mix of peptides from the thymus gland. The evidence grade is limited-human: studies in Russia and Ukraine report gains, but most are small or old. Source: https://peptideindex.ai/methodology#short-answer ## Known risks - FDA has not tested Thymalin products sold online for harm, benefit or quality [^1]. - FDA warned that a seller marketed Thymalin for children. Children may react more strongly to untested drugs [^1]. Source: https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/us-chem-labs-669074-02072024 ## What nobody knows yet - Nobody knows if Thymalin helps older people live longer. The long study of older people came from the group that developed it [^5] [^14]. - Nobody knows which parts of the extract do anything. A lab study points to two tiny peptides, but it used cells and computer models [^13]. - Some of the studies in people are written in Russian, with only a short English note. That makes them hard for others to check [^7] [^8]. - The results in rats, mice and lab-grown cells may not hold in people [^9] [^11] [^12]. Source: https://pubmed.ncbi.nlm.nih.gov/14523363/ ## What it is Thymalin is not one peptide. It is a mix of peptides taken from the thymus [^12]. The thymus is a gland in the chest that helps train the immune system. Researchers say two very short peptides in the mix may be its active parts [^13]. It was first taken from animal tissue by a research group in Russia [^14]. Doctors in Russia use it to support the immune system [^16]. It is also spelled Timalin [^15]. Thymulin and thymosin alpha-1 are different molecules, not Thymalin. No drug approved in the US contains it [^1]. Source: https://pubmed.ncbi.nlm.nih.gov/33237528/ ## Where it stands legally Thymalin has no approved use in the US: in 2024, FDA said Thymalin products sold online are new drugs with no approved application [^1]. That means no Thymalin product may be sold as a drug. It does not mean FDA found it harmful; FDA has not reviewed it [^1]. Its use in Russia does not change its US status. Checked 26 October 2026. FDA also said those products were misbranded. Their labels could not give directions a person could follow without a doctor [^1]. A label that says "research chemicals only" does not change this, FDA said [^1]. A pharmacy may make a drug from a bulk substance only in certain cases. One case is a substance on a list FDA keeps under section 503A of the law [^3]. FDA's list of nominated substances, updated in May 2026, does not name Thymalin [^2]. It names thymulin, a different molecule [^2]. Source: https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/us-chem-labs-669074-02072024 ## What the evidence shows The evidence grade is limited-human: studies in people report gains, but most are small, old or poorly described, and the ones that name a place were run in Russia and Ukraine [^5] [^6] [^7] [^8]. People: in a 2003 study, 266 older people were followed. Some got Thymalin, a pineal extract called Epithalamin, or both, for the first 2 to 3 years [^5]. Over 6 to 8 years, fewer people died in the treated groups than in the control group, the authors report [^5]. The study came from the group that developed Thymalin, and its summary does not say how people were put in groups [^5] [^14]. In a 2021 report, patients with COVID-19 got Thymalin on top of usual care [^6]. Blood signs of swelling and clotting fell faster [^6]. In 60 patients with lung tuberculosis, adding Thymalin to drugs shortened hospital stays, a 1990 report says [^7]. In 15 people with parkinsonism, a movement disorder, symptoms got better after a course of Thymalin [^8]. That study compared people only with themselves, before and after [^8]. Animals: in rats with a transplanted tumor, Thymalin stopped or shrank the tumor in more than half [^9]. In rats with a hole in the jaw bone, Thymalin shots given with a bone graft helped the bone heal [^10]. In old mice, it changed the mix of cells in bone marrow [^11]. Cells: in human stem cells in a lab, Thymalin pushed cells toward mature immune cells [^12]. In other lab tests, it lowered signals of swelling made by human blood cells [^13] [^14]. These are animal and lab results, not results in people. Source: https://pubmed.ncbi.nlm.nih.gov/14523363/ ## Legitimate ways to get it No approved drug in the US contains Thymalin, and FDA calls the products sold online unapproved new drugs [^1]. The federal list of substances pharmacies may use does not name it [^2] [^3]. There is no legal route to Thymalin in the US today. Any open trial would appear in the trials block below, with the date the official registry was last checked. Source: https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/us-chem-labs-669074-02072024 ## How people are getting it anyway This section describes what happens and is not a recommendation. One way of getting Thymalin shows up in federal records: websites that sell it as a research chemical [^1]. In 2024, FDA sent a warning letter to an online seller that offered Thymalin along with two weight-loss drugs [^1]. The seller's labels said the products were for research only and not for people [^1]. FDA said the website showed they were meant for people, so they are drugs [^1]. FDA said the Thymalin product had no approval and was misbranded [^1]. FDA was especially concerned that the seller marketed it for children [^1]. A law firm reports that FDA has stepped up action against peptides labeled for research use only [^4]. Source: https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/us-chem-labs-669074-02072024 ## Access routes Source: https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/us-chem-labs-669074-02072024 ### None Detail: There is no legal route to Thymalin in the US today. It is in no approved drug, and FDA calls Thymalin products sold online unapproved new drugs. Source: https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/us-chem-labs-669074-02072024 ## Unofficial channels Source: https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/us-chem-labs-669074-02072024 ### Research use seller What it is: Sold online as a research chemical, with a label saying it is not for people, while the website describes uses in people. Legal position: FDA says Thymalin products sold this way are drugs, because the website shows they are meant for people. They are unapproved new drugs and misbranded. (source: https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/us-chem-labs-669074-02072024) Documented risks: - FDA has not tested the product for harm, benefit or quality. (source: https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/us-chem-labs-669074-02072024) - FDA warned that the seller marketed Thymalin for children, who may react more strongly to untested drugs. (source: https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/us-chem-labs-669074-02072024) Enforcement: - 2024-02-07: FDA warning letter to an online seller of research chemicals; the letter names Thymalin as an unapproved new drug. (source: https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/us-chem-labs-669074-02072024) Source: https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/us-chem-labs-669074-02072024 ## Recruiting trials Snapshot date: 2026-10-26. 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=Thymalin&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://pubmed.ncbi.nlm.nih.gov/33237528/ ### 1. FDA warning letter to an online seller, naming Thymalin as an unapproved new drug, 7 February 2024 Type: regulatory Tier: primary Source: https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/us-chem-labs-669074-02072024 ### 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. Health Law Alliance: FDA action on peptides sold as research use only Type: legal-analysis Tier: legal-analysis Source: https://www.healthlawalliance.com/blog/fda-targets-glp-1-and-peptide-compounding-advertising-and-research-use-only-labeling ### 5. Thymalin and Epithalamin in 266 older people over 6 to 8 years, 2003 Type: human-trial Tier: peer-reviewed Source: https://pubmed.ncbi.nlm.nih.gov/14523363/ ### 6. Thymalin added to treatment of patients with COVID-19, 2021 Type: human-trial Tier: peer-reviewed Source: https://pubmed.ncbi.nlm.nih.gov/33575961/ ### 7. Thymalin with drug treatment in 60 patients with lung tuberculosis, 1990 Type: human-trial Tier: peer-reviewed Source: https://pubmed.ncbi.nlm.nih.gov/2080155/ ### 8. Thymalin in 15 patients with parkinsonism, 1999 Type: human-trial Tier: peer-reviewed Source: https://pubmed.ncbi.nlm.nih.gov/10424021/ ### 9. Thymalin and a transplanted sarcoma in rats, 2018 Type: animal Tier: peer-reviewed Source: https://pubmed.ncbi.nlm.nih.gov/29797130/ ### 10. Thymalin shots and jaw bone repair in rats, 2024 Type: animal Tier: peer-reviewed Source: https://pubmed.ncbi.nlm.nih.gov/38431810/ ### 11. Thymalin and bone marrow cells in mice of different ages, 2011 Type: animal Tier: peer-reviewed Source: https://pubmed.ncbi.nlm.nih.gov/21957575/ ### 12. Thymalin and human blood stem cells in a lab, 2020 Type: in-vitro Tier: peer-reviewed Source: https://pubmed.ncbi.nlm.nih.gov/33237528/ ### 13. Two short peptides in Thymalin, in cells and computer models, 2023 Type: in-vitro Tier: peer-reviewed Source: https://pubmed.ncbi.nlm.nih.gov/37686182/ ### 14. Thymalin and four other peptides in a human monocyte cell line, 2022 Type: in-vitro Tier: peer-reviewed Source: https://pubmed.ncbi.nlm.nih.gov/35408963/ ### 15. Review of clinical studies of peptide bioregulators, including Timalin, 2013 Type: reference Tier: peer-reviewed Source: https://pubmed.ncbi.nlm.nih.gov/24003726/ ### 16. Review of immune therapies used in Russian medicine, naming thymalin, 1999 Type: reference Tier: peer-reviewed Source: https://pubmed.ncbi.nlm.nih.gov/12687147/ Last verified: 2026-10-26. Sources: - https://clinicaltrials.gov/api/v2/studies?query.intr=Thymalin&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://pubmed.ncbi.nlm.nih.gov/14523363/ - https://pubmed.ncbi.nlm.nih.gov/24003726/ - https://pubmed.ncbi.nlm.nih.gov/33237528/ - https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/us-chem-labs-669074-02072024 [^1]: FDA warning letter to an online seller, naming Thymalin as an unapproved new drug, 7 February 2024 https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/us-chem-labs-669074-02072024 [^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]: Health Law Alliance: FDA action on peptides sold as research use only https://www.healthlawalliance.com/blog/fda-targets-glp-1-and-peptide-compounding-advertising-and-research-use-only-labeling [^5]: Thymalin and Epithalamin in 266 older people over 6 to 8 years, 2003 https://pubmed.ncbi.nlm.nih.gov/14523363/ [^6]: Thymalin added to treatment of patients with COVID-19, 2021 https://pubmed.ncbi.nlm.nih.gov/33575961/ [^7]: Thymalin with drug treatment in 60 patients with lung tuberculosis, 1990 https://pubmed.ncbi.nlm.nih.gov/2080155/ [^8]: Thymalin in 15 patients with parkinsonism, 1999 https://pubmed.ncbi.nlm.nih.gov/10424021/ [^9]: Thymalin and a transplanted sarcoma in rats, 2018 https://pubmed.ncbi.nlm.nih.gov/29797130/ [^10]: Thymalin shots and jaw bone repair in rats, 2024 https://pubmed.ncbi.nlm.nih.gov/38431810/ [^11]: Thymalin and bone marrow cells in mice of different ages, 2011 https://pubmed.ncbi.nlm.nih.gov/21957575/ [^12]: Thymalin and human blood stem cells in a lab, 2020 https://pubmed.ncbi.nlm.nih.gov/33237528/ [^13]: Two short peptides in Thymalin, in cells and computer models, 2023 https://pubmed.ncbi.nlm.nih.gov/37686182/ [^14]: Thymalin and four other peptides in a human monocyte cell line, 2022 https://pubmed.ncbi.nlm.nih.gov/35408963/ [^15]: Review of clinical studies of peptide bioregulators, including Timalin, 2013 https://pubmed.ncbi.nlm.nih.gov/24003726/ [^16]: Review of immune therapies used in Russian medicine, naming thymalin, 1999 https://pubmed.ncbi.nlm.nih.gov/12687147/