Thymalin
Also sold as: Timalin, Тималин, thymus polypeptide complex
Thymalin, a polypeptide extract of calf thymus, is not an FDA-approved drug: FDA named a 'Thymalin' product as an unapproved new drug and a misbranded drug in a February 2024 warning letter, stating that no application under section 505 of the Federal Food, Drug, and Cosmetic Act is in effect for it, and thymalin appears in no category of FDA's 503A bulk drug substances list. Thymalin has genuinely been administered to humans — in a 2021 single-centre, open-label, randomised controlled trial, 42 hospitalised COVID-19 patients received it intramuscularly alongside standard care — but that trial reported laboratory markers only, with no clinical outcomes and no adverse-event data.
Which molecule this is. Thymalin is not a defined synthetic peptide. The 2021 trial describes it as 'a complex of peptides isolated from the thymus of calves with a molecular weight of up to 10 kDa' — an animal-tissue extract, manufactured by Samson-Med LLC (St. Petersburg) and identified in that paper by a drug series number. Three separate substances are routinely collapsed into this name and should not be: (i) thymalin, the calf-thymus extract; (ii) the Lys-Glu (KE) and Glu-Trp (EW) dipeptides described in a 2023 paper as active substances of thymalin and sold separately; and (iii) thymosin alpha-1 (thymalfasin), a defined 28-amino-acid peptide with its own record on this site. FDA has ruled on exactly this extract-versus-analogue question for the pineal pair from the same Russian research programme, holding that epithalamin (the gland extract) and epitalon (the synthetic tetrapeptide) 'are different substances' — so a study of the extract is not evidence about the analogue, and the reverse also holds.
FDA status
FDA has not approved this and it is not in active development toward approval. That says nothing about whether it is being sold — most substances in this category are.
Sourced to an FDA document that names thymalin, rather than to an absence. Drugs@FDA was queried four ways on 2026-08-02 via the openFDA API — openfda.generic_name, openfda.brand_name, openfda.substance_name and products.active_ingredients.name — and all four returned NOT_FOUND, with a semaglutide control query on the same field returning six applications, so the empty result is a fact about the database and not an artifact of the query. That is still only an absence, which is why the sourced quote is FDA's own affirmative statement that no section 505 application is in effect. NOT 'investigational', and the distinction is the one this vocabulary exists to hold: a ClinicalTrials.gov API query for 'thymalin' on 2026-08-02 returned an empty study list — not one registration, anywhere, by anyone. There is no identifiable sponsor pursuing US approval, so there is no development programme to be in. Separately, and this is where readers get misled in the other direction: the 2021 trial authors state that thymalin 'has been approved by the Ministry of Health of the Russian Federation for medical use since 1982' and give a manufacturer and a registration certificate number. We did NOT independently verify that against the Russian State Register of Medicines, and we record it as the authors' statement rather than as a verified fact. Even if it is exactly right, a Russian registration is not an FDA status and confers nothing in the United States.
“No approved applications pursuant to section 505 of the FD&C Act, 21 U.S.C. 355 are in effect for these products.”Checked against the source on .
Evidence
There is human data, but efficacy is not established. This includes programmes that were tested and failed.
Administration check RUN AND PASSED on the full text, not on an abstract. In Khavinson et al. 2021 thymalin was given intramuscularly to 42 hospitalised COVID-19 patients against 50 standard-care controls; the paper is open access in PubMed Central and states its own design in the sentence quoted above. The endogenous-biomarker trap that reduces MOTS-c's apparent four human RCTs to zero cannot apply to thymalin at all: it is a manufactured calf-thymus extract with a named manufacturer and a lot number, and there is no endogenous 'thymalin' in a person to measure by mistake. WHY THIS IS NOT 'PROVEN', and the list is long. The 2021 trial was open-label with no placebo, single-centre, and reported ONLY laboratory endpoints — IL-6, C-reactive protein, D-dimer, fibrinogen, ferritin, CD3/CD4/CD8 counts and blood cell ratios. Read against a text search of the full paper, the words 'adverse', 'safety', 'tolerability', 'placebo', 'blind', 'died' and 'discharge' do not appear ANYWHERE in it. No mortality, no ventilation, no length of stay, no adverse-event table: the trial measured markers, not patients' outcomes. Co-interventions were heavy and unbalanced — hydroxychloroquine and lopinavir/ritonavir, both since abandoned for COVID-19, were given to differing proportions of the two arms — and the paper reports no trial registration and no power calculation. The senior author is at the Saint Petersburg Institute of Bioregulation and Gerontology, the institute behind thymalin's development; the paper's declaration reads 'There is no conflict of interest.' THE OTHER HUMAN STUDY, and it is the one the consumer market actually runs on: Khavinson and Morozov 2003 reports thymalin and epithalamin given to 266 elderly persons over 6-8 years with mortality reported as several-fold lower than control. PubMed indexes it as a Randomized Controlled Trial, but the ABSTRACT describes no randomisation, no blinding and no allocation method, and the full text we located is a scanned image with no extractable text — so nothing about its design was confirmed beyond the MEDLINE publication-type tag. An extraordinary mortality claim from a single research group in a low-circulation journal, whose methods we could not read, is not something this record will carry as established. BREADTH DOES NOT RESCUE IT EITHER. PubMed indexes roughly a dozen further thymalin studies tagged Clinical Trial or Randomized Controlled Trial — in tuberculosis, peritonitis, erysipelas, dysentery, ulcerative colitis, parkinsonism and schizophrenia, dating from 1982 to 2007 — and every one of them is Russian- or Ukrainian-language, none was opened for this record, and none is counted toward this tier. Counting them would be the exact error the editorial policy names. The tier rests on one trial that was read.
“The single-center, open-label, prospective, randomized, controlled trial included patients hospitalized in St. Petersburg City General Hospital No. 2 with a clinical diagnosis of U07.1, COVID-19, virus identified, during April - July 2020. […] All patients were divided into 2 groups: the main group consisted of 42 patients (25 women and 17 men) who received treatment according to the standard regimen in combination with thymalin; the control group included 50 patients (27 women and 23 men) who received treatment according to the standard regimen.”Checked against the source on .
What FDA found
FDA’s own words. These are the most citable thing on this site, and the least likely to appear anywhere funded by someone selling the compound.
FDA identified a 'Thymalin' product by name as an unapproved new drug, in a February 7, 2024 warning letter to US Chem Labs of Miami, Florida, alongside that seller's semaglutide and tirzepatide products.
This is the finding that distinguishes thymalin from most of the research-chemical market, where FDA's position has to be inferred from a substance's absence from a list. Here FDA wrote the sentence. Note what makes a product a 'new drug' in FDA's reasoning: not the molecule's novelty but the seller's claims — FDA states the products 'are not generally recognized as safe and effective for the above referenced uses and, therefore, are new drugs under section 201(p) of the FD&C Act.' The uses came off the website.
US Chem Labs — Warning Letter, MARCS-CMS 669074 — FDA, 7 February 2024“your 'Semaglutide,' 'Tirzepatide' and 'Thymalin' products are unapproved new drugs introduced or delivered for introduction into interstate commerce in violation of sections 505(a) and 301(d) of the Federal Food, Drug, and Cosmetic Act (FD&C Act), 21 U.S.C. 355(a) and 301(d).”
Checked against the source on .FDA rejected the 'research chemicals only' and 'not for human consumption' labelling on the thymalin product, holding that website evidence established the products were intended to be drugs for human use.
Record this as a legal theory that FAILED, because it is the theory nearly every thymalin vendor still relies on. The disclaimer did not defeat intended use; FDA read the site copy and treated the claims on it as the evidence. FDA's word in the letter is 'Despite'. A product sold with a research-use disclaimer and a page explaining what it does for the immune system is, on FDA's reading, a drug being sold without an approved application.
US Chem Labs — Warning Letter, MARCS-CMS 669074 — FDA, 7 February 2024“Despite statements on your product labeling marketing your products as 'research chemicals only' and 'not for human consumption,' evidence obtained from your website establishes that your products are intended to be drugs for human use.”
Checked against the source on .FDA stated it was 'particularly concerned' that the seller marketed its thymalin product for use in children, and that the product had not been evaluated by FDA for safety, effectiveness, and quality.
FDA singled out the paediatric marketing for its own paragraph — the letter's only product-specific escalation, and it attaches to thymalin rather than to the two GLP-1 products. FDA's stated reason is that 'The use of untested drugs can have unpredictable and unintended consequences, especially in vulnerable populations such as children and infants'. FDA repeated the point in its own press summary the following week, describing the product as offered 'for both adults and children, for treatment of various conditions, such as immunosuppression after chemotherapy in cancer patients.' The paediatric indication is not an American invention: it tracks the Soviet-era label the seller reproduced.
US Chem Labs — Warning Letter, MARCS-CMS 669074 — FDA, 7 February 2024“In addition, FDA is particularly concerned that you market your 'Thymalin' product for use in children. Your product has not been evaluated by FDA for safety, effectiveness, and quality.”
Checked against the source on .FDA also found the thymalin product misbranded, on the ground that its labeling fails to bear adequate directions for use and that it is a prescription drug for which such directions cannot be written for a layperson.
Two independent violations, not one, and the second is the one with teeth. Misbranding under 502(f)(1) turns on how the product was LABELLED, which means it does not depend on resolving anything about thymalin's biology, its Russian registration, or any evidence question. It is also the provision that carries criminal exposure in this market generally. Approval status and labelling exposure are separate questions with separate answers.
US Chem Labs — Warning Letter, MARCS-CMS 669074 — FDA, 7 February 2024“Your 'Semaglutide,' 'Tirzepatide' and 'Thymalin' products are also misbranded under section 502(f)(1) of the FD&C Act, 21 U.S.C. 352(f)(1), in that their labeling fails to bear adequate directions for their intended use(s).”
Checked against the source on .Thymalin appears in none of the three categories of FDA's 503A bulks list updated May 14, 2026, and does not appear in FDA's table of bulk drug substances 'nominated but withdrawn' — the table that carries AOD-9604, BPC-157, cathelicidin LL-37, CJC-1295, dihexa acetate, emideltide, epitalon, GHK-Cu and ipamorelin acetate.
Both documents were fetched with a browser user-agent and text-extracted locally on 2026-08-02; 'thymalin' returns zero hits in each. Be precise about what that does and does not establish. It establishes ABSENCE — thymalin is in no category and on no list. It does NOT establish that thymalin was never nominated, which is why this record carries no 503A compounding status at all rather than asserting one. The operative consequence for a reader stands on the absence alone and needs nothing further: a bulk drug substance that is neither the subject of a USP monograph nor a component of an approved drug must appear on the 503A bulks list to be used in 503A compounding, and thymalin does not appear on it.
Bulk Drug Substances Nominated for Use in Compounding Under Section 503A of the Federal Food, Drug, and Cosmetic Act — FDA, 14 May 2026“Visit Safety Risks Associated with Certain Bulk Drug Substances for Use in Compounding for a summary of the identified safety risks for bulk drug substances in category 2, as well as other bulk drug substances that were previously in category 2 but were withdrawn.”
Checked against the source on .Across all seven FDA briefing documents prepared for the July 23-24, 2026 Pharmacy Compounding Advisory Committee meeting, the word 'thymalin' appears exactly once — on page 61 of the epitalon document, inside the nomination material FDA reproduced, not in FDA's own analysis. FDA has published no evaluation of thymalin.
All seven briefing documents were downloaded and text-extracted on 2026-08-02: BPC-157, emideltide, KPV, MOTS-c, semax and TB-500 return zero hits for 'thymalin'; the epitalon document returns one, on page 61, which falls after the divider page headed 'Epitalon-Related Bulk Drug Substances … Nominations'. It is the nominator's narrative, not FDA's — the sentence claims a mortality rate 4.1 times lower in people given thymalin and epithalamin, and it is reproduced there as submitted material. Do not cite it as an FDA finding. What IS in FDA's own voice is the quoted sentence, and it matters twice over. First, FDA read Khavinson and Morozov 2003 — the same paper the thymalin longevity claim rests on — and set it aside as evidence about a different substance than the one under evaluation. Second, the same document records that FDA 'could not evaluate the full article by Korkorshko et al. 2007 because it was in the Russian language' and 'searched multiple databases and were unable to locate the full article in English.' That is the procedural reality for a literature that is almost entirely Russian: FDA does not read it. Thymalin has never been through a PCAC evaluation, so no FDA staff proposal on it exists either way.
Epitalon-Related Bulk Drug Substances — FDA Briefing Document, Pharmacy Compounding Advisory Committee Meeting, July 23-24, 2026 — FDA, 23 July 2026“Seven of the articles submitted (Anisimov et al. 2001a; Khavinson and Morozov 2003; Korkushko et al. 2004; Korkushko et al. 2006; Korkushko et al. 2011; Labunets et al. 2007; Slepushkin et al. 1983) discussed the use of epithalamin; however, we note that epitalon and epithalamin are different substances.”
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Documented safety signals
FDA states the thymalin product it examined 'has not been evaluated by FDA for safety, effectiveness, and quality', and that untested drugs can have unpredictable and unintended consequences, especially in children and infants.
An information gap, stated by FDA, not a documented harm — and the two are different things that this market habitually merges in the wrong direction. Our own FAERS query through the openFDA drug/event endpoint on 2026-08-02 returned no reports for 'THYMALIN' or 'TIMALIN'. That is what we checked, not a demonstration of safety: a substance sold under a research-use label, by sellers FDA says are marketing it as a drug, is exactly the kind of exposure that does not reach FAERS at all.
US Chem Labs — Warning Letter, MARCS-CMS 669074 — FDA, 7 February 2024“Your product has not been evaluated by FDA for safety, effectiveness, and quality. The use of untested drugs can have unpredictable and unintended consequences, especially in vulnerable populations such as children and infants who may be at greater risk for adverse reactions associated with certain drug products due to differences in the ability of children to absorb, metabolize, distribute, or excrete such drug products or their metabolites.”
Checked against the source on .The one randomised controlled trial of thymalin available in English full text reports no adverse-event data of any kind: the words 'adverse', 'safety' and 'tolerability' do not appear in it.
Verified by full-text search of the PMC copy on 2026-08-02, and recorded because the absence is easy to mistake for a clean result. Ninety-two hospitalised patients were followed, 42 of them given thymalin, and the paper reports laboratory markers only — no adverse events, no tolerability assessment, no deaths, and no discharge or ventilation outcomes. A trial that did not look for harm cannot report finding none. Anyone citing this trial as evidence that thymalin is well tolerated is citing a section of it that does not exist.
Results and Prospects of Using Activator of Hematopoietic Stem Cell Differentiation in Complex Therapy for Patients with COVID-19 (Khavinson, Kuznik, Trofimova et al.) — Stem Cell Reviews and Reports (PubMed Central, PMC7877506), 11 February 2021Checked against the source on .
Questions people actually ask
Every answer cites the document behind it. Where the honest answer is “nobody knows”, that is the answer you will get.
- Is Thymalin FDA-approved?
No. FDA named a 'Thymalin' product as an unapproved new drug in a warning letter dated February 7, 2024 to US Chem Labs, and stated plainly that 'No approved applications pursuant to section 505 of the FD&C Act, 21 U.S.C. 355 are in effect for these products.' A search of Drugs@FDA through the openFDA API returns no match for thymalin under generic name, brand name, substance name or active ingredient. Thymalin is also not in clinical development toward US approval: ClinicalTrials.gov registers no thymalin study at all. The 2021 trial authors state the drug has been approved by the Ministry of Health of the Russian Federation since 1982, which is a Russian registration and not an FDA status.
US Chem Labs — Warning Letter, MARCS-CMS 669074 — FDA, 7 February 2024“No approved applications pursuant to section 505 of the FD&C Act, 21 U.S.C. 355 are in effect for these products.”
Checked against the source on .- Is there any human evidence that Thymalin works?
Yes, thymalin has been administered to humans — but the strongest study readable in English measured laboratory markers rather than whether anyone got better. In a 2021 trial its authors describe as 'single-center, open-label, prospective, randomized, controlled', 42 hospitalised COVID-19 patients in St. Petersburg received thymalin intramuscularly alongside standard therapy and 50 received standard therapy alone; the investigators reported faster decline in interleukin-6, C-reactive protein and D-dimer in the thymalin group. The trial had no placebo, no blinding, no registration, and reported no mortality, ventilation, discharge or adverse-event outcomes. Roughly a dozen further thymalin trials are indexed in PubMed from 1982 to 2007, in tuberculosis, peritonitis, ulcerative colitis and other conditions, but all are Russian- or Ukrainian-language and none was opened for this record. FDA has published no evaluation of any of them.
Results and Prospects of Using Activator of Hematopoietic Stem Cell Differentiation in Complex Therapy for Patients with COVID-19 (Khavinson, Kuznik, Trofimova et al.) — Stem Cell Reviews and Reports (PubMed Central, PMC7877506), 11 February 2021“The single-center, open-label, prospective, randomized, controlled trial included patients hospitalized in St. Petersburg City General Hospital No. 2 with a clinical diagnosis of U07.1, COVID-19, virus identified, during April - July 2020.”
Checked against the source on .- Can I legally buy Thymalin as a research chemical?
A research-use disclaimer did not work for the one thymalin seller FDA has written to. In its February 2024 warning letter FDA held: 'Despite statements on your product labeling marketing your products as research chemicals only and not for human consumption, evidence obtained from your website establishes that your products are intended to be drugs for human use.' FDA then found the thymalin product both an unapproved new drug under sections 505(a) and 301(d) and a misbranded drug under section 502(f)(1), because its labeling fails to bear adequate directions for its intended use. The claims on the seller's own page were the evidence FDA used. Note that the misbranding finding turns on labelling rather than on any question about thymalin itself.
US Chem Labs — Warning Letter, MARCS-CMS 669074 — FDA, 7 February 2024“Despite statements on your product labeling marketing your products as 'research chemicals only' and 'not for human consumption,' evidence obtained from your website establishes that your products are intended to be drugs for human use.”
Checked against the source on .- Was Thymalin part of the July 2026 FDA advisory committee meeting on peptides?
No. The seven substances before the Pharmacy Compounding Advisory Committee on July 23-24, 2026 were BPC-157, emideltide (DSIP), epitalon, KPV, MOTS-c, semax and TB-500. Thymalin was not among them and has never been evaluated by that committee, so no FDA staff proposal on thymalin exists in either direction. Across all seven briefing documents the word 'thymalin' appears exactly once, on page 61 of the epitalon document, inside the nomination material FDA reproduced rather than in FDA's own analysis. Thymalin also appears in no category of FDA's 503A bulks list, so a 503A pharmacy has no lawful basis to compound from it.
Pharmacy Compounding Advisory Committee Meeting, July 23-24, 2026 — Agenda — FDA, 23 July 2026“During the morning session, the committee will discuss the following bulk drug substances being considered for inclusion on the list of bulk drug substances that can be used to compound drug products in accordance with section 503A of the FD&C Act: BPC-related bulk drug substances (BPC-157 (free base) / BPC-157 acetate) and KPV-related bulk drug substances (KPV (free base) / KPV acetate).”
Checked against the source on .- Is Thymalin the same thing as thymosin alpha-1?
No. Thymalin is a polypeptide complex extracted from calf thymus, described in a 2021 trial as 'a complex of peptides isolated from the thymus of calves with a molecular weight of up to 10 kDa'. Thymosin alpha-1 (thymalfasin) is a single defined 28-amino-acid peptide with its own regulatory and evidence record. Thymalin is also distinct from the Lys-Glu and Glu-Trp dipeptides that a 2023 paper describes as its active substances and that are sold separately. FDA has drawn precisely this distinction for the equivalent pineal pair from the same Russian research programme, holding that the gland extract epithalamin and the synthetic tetrapeptide epitalon 'are different substances' — which means evidence about one is not evidence about the other.
Results and Prospects of Using Activator of Hematopoietic Stem Cell Differentiation in Complex Therapy for Patients with COVID-19 (Khavinson, Kuznik, Trofimova et al.) — Stem Cell Reviews and Reports (PubMed Central, PMC7877506), 11 February 2021“One of these drugs is thymalin, which is a complex of peptides isolated from the thymus of calves with a molecular weight of up to 10 kDa.”
Checked against the source on .- Did FDA say anything about Thymalin being sold for children?
Yes. FDA stated in its February 2024 warning letter: 'In addition, FDA is particularly concerned that you market your Thymalin product for use in children. Your product has not been evaluated by FDA for safety, effectiveness, and quality.' FDA gave as its reason that untested drugs 'can have unpredictable and unintended consequences, especially in vulnerable populations such as children and infants', and repeated the point in its own press summary of February 13, 2024, which described the seller as offering thymalin 'for both adults and children, for treatment of various conditions, such as immunosuppression after chemotherapy in cancer patients.' This was the only product-specific escalation in a letter that also covered semaglutide and tirzepatide.
FDA Roundup: February 13, 2024 — FDA, 13 February 2024“In addition, the firm offers a product called 'thymalin' (not related to semaglutide or tirzepatide) for both adults and children, for treatment of various conditions, such as immunosuppression after chemotherapy in cancer patients.”
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