Thymalin

Areas of active research — not promised effects

Each tag links to other compounds with research into that goal. Research use only: these are areas of study, not human-use claims.

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Thymalin is not FDA-approved for any indication and has no USP/NF monograph. It does not appear on FDA's 503A or 503B bulk drug substances lists. It was not among the ~14 peptides signaled for Category 1 reclassification in the February 2026 HHS announcement (docket FDA-2025-N-6895), and no explicit Category 2 listing was found; however, it lacks any lawful compounding pathway under federal law. Sale for human use is not authorized.

Transparent blend · bci-1.0 · never paid-placement

Primary name

Thymalin

Origin

Thymalin is a standardized polypeptide extract derived from calf thymus glands, containing multiple bioactive peptide fractions in the ~1–10 kDa molecular weight range. It was developed in the 1970s by Vladimir Khavinson and Vyacheslav Morozov at the Military Medical Academy in Saint Petersburg, Russia, and has been registered as an immunomodulatory drug in Russia since 1982. It is distinct from thymulin (a single zinc-dependent nonapeptide; CAS 63958-90-7) — see identity flag below.

Registry IDs

PubChem CID

3085284

CAS

63958-90-7

InChIKey

LIFNDDBLJFPEAN-BPSSIEEOSA-N

DrugBank

DB20426

ChEMBL

CHEMBL2106455

Molecular formula

C33H54N12O15

Molar mass

858.9 g/mol

Monoisotopic

858.38315906 Da

InChIKey

LIFNDDBLJFPEAN-BPSSIEEOSA-N

Appearance

White to off-white lyophilized powder (vendor-typical for the RUO synthetic nonapeptide form sold as thymalin; the original biological extract may differ)

Solubility

Soluble in water; typically reconstituted in bacteriostatic water or sterile sal…

Sequence not available in current seed.

Stability: Peptide mixtures are generally susceptible to enzymatic degradation and oxidation; stability data for thymalin as a defined mixture are not available from peer-

Vial sizes

10 mg · 20 mg

Purity grades

research grade

Salt forms

Free base (primary)

• GHS hazard class on file
• PPE & spill response
• Disposal guidance
• Not-for-human-consumption posture

How much research exists, and of what maturity — never a verdict on whether it works.

Mechanism of action

• Thymalin's immunomodulatory activity is attributed primarily to short constituent peptides (including the dipeptides Lys-Glu and Glu-Trp, among others) that are thought to bind double-stranded DNA and histone proteins, thereby modulating expression of immune-related genes and promoting differentiation of precursor T-lymphocytes
• Research has shown it stimulates T-lymphocyte differentiation, enhances natural killer cell activity, and corrects dysregulated immune parameters in immunodeficient states
• Its effects on thymic stromal cells may support maturation of naive T-cell precursors into functional lymphocytes, a mechanism relevant to age-associated thymic involution
• Despite a short plasma half-life, immunological effects on T-cell subsets and lymphocyte redistribution have been reported to persist 24–48 hours after a single dose in preclinical models

Pharmacokinetics (ADME)

Half-life

~3–6 hours (subcutaneous; vendor/non-peer-reviewed source; no peer-reviewed PK study identified)

Clearance

Reported renal filtration and enzymatic degradation; no peer-reviewed PK data found

PK–PD note: No peer-reviewed pharmacokinetic study identified for thymalin as a defined mixture. PK figures in circulation derive from vendor or grey-literature sources and should be treated with caution.…

Reading the evidence

• Evidence quality and gaps vary by application — see the cited grades above.
• Indexed-article counts span all evidence tiers, not only completed human trials.
• No first-party human-dosing, efficacy, or benefit claims are made here.

Key reviews & evidence-gap sources

• Khavinson VKh, Linkova NS, Chalisova NI, Ivko OM. The Use of Thymalin for Immunocorrection and Molecular Aspects of Biological Activity. Biol Bull Rev. 2021;11(4):377-382. — Mechanism-focused review by the drug's originator group; describes KE/EW/EDP dipeptide/tripeptide components and gene-expression regulation.
• Kuznik B, Khavinson V, et al. Peptide Drug Thymalin Regulates Immune Status in Severe COVID-19 Older Patients. Adv Gerontol. 2021;11(4):368-376. — Russian open-label clinical study (n=36 Thymalin vs n=44 control); not registered on ClinicalTrials.gov; reports mortality reduction — high-stakes efficacy claim.
• Wolf E, Milazzo S, Boehm K, Zwahlen M, Horneber M. Thymic peptides for treatment of cancer patients. Cochrane Database Syst Rev. 2011;(2):CD003993. — Only located systematic review of thymic peptides; covers thymostimulin/thymosin fraction 5/thymopentin/thymosin α1 — does NOT include Thymalin specifically. Found no OS/DFS/TR benefit for purified thymus extracts.
• Review of Thymic Peptides and Hormones: From Their Properties to Clinical Application. Int J Pept Res Ther. 2024. — Broad thymic-peptide review; notes TH (thymosin) preparation never entered clinical trials; contextualizes thymalin within the thymic-peptide family.

No registered human trials found for this compound.

Status

No registered trials found

Summary (literature)

Published clinical literature from the Khavinson group reports a favorable short-term tolerability profile over 35+ years of clinical use in Russia, with no serious adverse events attributed to thymalin in the reported studies. Common observations are injection-site reactions wit…

WADA status

Not specifically listed by name on the WADA 2026 Prohibited List. However, thymic peptides with growth factor or immune-modulating activity may fall under the S…

Dominant research route: Intramuscular (IM) injection

Human clinical use; randomized controlled study in severe COVID-19 older patients (investigation group n=36 vs control n=44), Thymalin 10 mg in 2 mL 0.9% NaCl administered as intramuscular injections daily for 10 days

Bioavailability: Polypeptide complex isolated from calf thymus; administered as 10 mg/2 mL saline IM. No plasma PK parameters reported in the cited study; efficacy endpoints were clinical/immunological (lymphocyte counts, CRP, D-dimer, NK cells, mortality).

IM is the route used in the published Russian clinical literature and the registered drug (Russian Ministry of Health registration LS-000267, 26 Feb 2010). Describes what was studied, not a protocol recommendation.

Community/anecdotal use; not the route used in the cited human RCTs (which used IM). Aggregator sources state SC is used as an alternative to IM.

Bioavailability: No primary PK data located; aggregator sources assert the small dipeptide components are absorbed from subcutaneous tissue, but this is not supported by retrieved primary literature.

SC route appears in community/aggregator guidance rather than the published clinical trials. Treated as de-identified aggregate community practice, not cited efficacy.

Not studied as an effective systemic route; mechanistic/aggregate reasoning that gastric and pancreatic proteases degrade the peptide before absorption.

Bioavailability: Oral systemic bioavailability described as effectively negligible due to gastric and pancreatic protease degradation prior to absorption. This is a stability/degradation note, not an absorption/PK measurement.

Oral-stability note only (peptide degradation in GI tract); does not constitute evidence of oral absorption. No retrieved primary PK study quantifies oral bioavailability.

Experimental/anecdotal; aggregator sources note some practitioners report sublingual use, with uncertain bioavailability and no supporting primary data.

Bioavailability: Bioavailability uncertain; the small dipeptide size is speculated to permit some mucosal absorption but this has not been demonstrated.

Sublingual route is described as highly experimental with very limited data in aggregator/community sources; no retrieved primary study.

Animal & human figures are kept visibly separate so studied animal doses are never misread as human guidance.

Sorted A–Z by vendor — never by price

Weekly median $/mg from the live vendor crawl.

Researched storefront prices, bucketed

p25 $0.790 · median $1.60 · p75 $2.65 · 8 researched vendors

Legit, COA-backed band: $0.500–$5.52/mg.

Value rule: don't just buy the cheapest — a price under $3/mg is a red flag. Pair price with COA and independent-test grade.

Estimated cost of research (10 mg)

Vial (best researched price)

$5

Bacteriostatic water (generic estimate)

$6

Syringes / supplies (generic estimate)

$12

What each test proves — general guidance, plus this compound's researched purity data

Purity on the current market (researched)

Vendor-claimed purity of ≥99% (HPLC) is widely advertised by research-peptide retailers (e.g., American Peptides '≥99% (HPLC Verified)'; Biotech Peptides '99% purity'). No independently verified purity dataset for Thymalin was retrievable from a primary lab report in this search; one retailer-published lab-report index (VerifiedPeptides) listed a Thymalin batch at 99.764% purity (batch 01-26-0710G, dated 2025-12-31), but the page could not be directly retrieved/verified.

Independent labs cited for this compound

No FDA recall, market withdrawal, or safety alert specifically naming Thymalin was found in the FDA Recalls / Safety Alerts databases reviewed. The only compound-specific federal enforcement action located is the 2024 FDA Warning Letter to US Chem Labs naming Thymalin as an unapproved/misbranded new drug.

Buyer red-flag checklist

• 'Research chemicals only' / 'not for human consumption' labeling coexisting with disease-treatment claims (immune/endocrine/cardiovascular 'benefits') — the exact pattern FDA cited as establishing human-drug intended use in the US Chem Labs warning letter.
• Persistent conflation of Thymalin (thymic polypeptide complex) with synthetic Thymulin (nonapeptide, FTS) across vendors and literature — different molecular weights, synthesis pathways, and regulatory histories; sourcing/identity errors are common.
• Historical/Soviet-era thymalin preparations described as containing only ~60–80% active thymic fraction, versus modern synthetic ≥98–99% claims — purity/standardization varies materially by source and era.
• No FDA-approved Thymalin product exists; all U.S. supply is unapproved research-grade with no GMP/sterility guarantee for human use.
• HPLC 'purity' (UV-detectable species only) can mask peptide-content underdosing by UV-inactive excipients; vendor COAs rarely report net peptide content separately.
• Thymalin/Thymulin is not specifically named on the WADA Prohibited List, but thymic peptides with immunomodulatory activity may implicate S2 (Peptide Hormones, Growth Factors) categories — athletes should verify status.

GMP vs research-grade: the chemistry (SPPS + HPLC + MS) is identical — the difference is the quality system.

Underdosing / mislabeling: No independent third-party lab test results (Janoshik/MZ Biolabs/Finnrick aggregates) quantifying Thymalin underdosing or peptide-content shortfall were retrievable. A secondary caution: HPLC 'purity' does not equal peptide content/mass — UV-inactive fillers (e.g., mannitol) can yield ~99% HPLC purity while diluting actual peptide mass, a known general pitfall for lyophilized research peptides.

• FDA Import Alert 66-41 ('Detention Without Physical Examination of Unapproved New Drugs') authorizes DWPE of unapproved new drug products not on the Red List. It is a generic, non-Thymalin-specific mechanism; Thymalin (an unapproved new drug per the 2024 US Chem Labs warning letter) would fall within its scope when offered for human use, but Thymalin is not individually named on the alert.IA 66-41
• An RUO label is not an import exemption — CBP judges actual intended use.
• Lyophilized powder is ambient-stable in transit; temperature control needed for > 7-day transit.
• US-warehouse vendors dodge import scrutiny — they cost more but ship more reliably.

Every item dated & sourced

Not specifically named on the WADA 2026 Prohibited List; potential S0 (non-approved substances) catch-all exposure if used in competition context.

No granted patents identified in current seed. Composition-of-matter coverage is limited given the peptide's synthetic origin.

• IACUC / IRB research context
• RUO buyer responsibilities & documentation
• Veterinary / alternative-use where lawful
• Jurisdiction-aware "who may lawfully obtain"

What people discuss

Reported concerns — discussion, not established effects

Reading caveats

• Vendor-affiliated content (Particle Peptides, Direct Peptides, Real Peptides, Swolverine, Jay Campbell) promoting use
• Anecdotal self-report dominant over controlled data
• Single-school (Khavinson) evidence base repeatedly cited
• Frequent conflation of Thymalin/Thymulin/Thymosin Alpha-1 inflating perceived effects
• Russian-language labeling and extract standardization variability complicating identity claims

Manually researched from reddit, youtube— theme weights are research estimates, not live counts; aggregated & de-identified. No individual posts, quotes, or usernames are ever shown.

Relative research / market volume — populated once the activity stream is wired

Inline tooltips for lyophilized, RUO, EU/mg, SPPS, 503A and more.

Toggle plain-language ↔ scientific in the header.

• How to read a COA
• Free base vs acetate
• Understanding evidence grades

Calf thymus polypeptide extract studied for T-cell maturation, immune restoration, and age-related immune decline in Russian clinical literature. Approximately 287 articles are indexed (literature last scanned 2026-05-29). US regulatory status: Research Use Only — no lawful compounding pathway. Research use only.

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