Thymalin
$54.00
Thymalin is a heterogeneous thymic polypeptide complex originally isolated from young calf thymus tissue. Unlike single synthetic peptides, it has no single molecular formula or PubChem CID and is composed of multiple bioactive short peptide fractions, including KE dipeptide, EW dipeptide, and EDP.
It is distinct from Thymulin, a defined zinc-dependent nonapeptide often confused with Thymalin in the peptide market. In the United States, Thymalin is not FDA-approved and has been specifically cited in FDA enforcement action as an unapproved new drug, making accurate, educational, and non-therapeutic positioning essential. (strength: 10mg)
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Thymalin (Bovine Thymus Polypeptide Bioregulator)
Constituent Peptides: PubChem CID 7010502 (KE/Vilon) | CID 100094 (EW/Thymogen) | CID 71300623 (Thymulin)
CAS 79621-14-0 (Complex) | MW Range: 1,000–10,000 Da | Thymic Immunomodulatory Polypeptide
Bovine Thymus Extract | Khavinson Bioregulator | FDA-Confirmed Unapproved Drug | Research Use Only
REGULATORY STATUS — READ BEFORE PROCEEDING Thymalin (CAS 79621-14-0) is a naturally derived, heterogeneous polypeptide complex extracted from the thymus glands of young calves (bovine source) via enzymatic hydrolysis and lyophilization. It is NOT approved by the U.S. Food and Drug Administration (FDA) for any human or veterinary indication. No IND, NDA, or ANDA exists for Thymalin in the United States.
Critically, the FDA explicitly named “Thymalin” in a formal warning letter (MARCS-CMS 669074, February 7, 2024) issued to US Chem Labs. The letter cited Thymalin products as unapproved new drugs introduced 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 331(d). The warning specifically flagged marketing claims associating Thymalin with treatment of immunosuppression after chemotherapy in cancer patients and use in children aged 6 months to 14 years — framing that constitutes misbranding under Section 502. This makes Thymalin one of the very few thymic peptides to receive a named, compound-specific FDA enforcement citation.
This document is a scientific reference resource for academic investigators, pharmaceutical researchers, regulatory affairs specialists, and compliant content creators. It is NOT a product listing, NOT a dosing guide, NOT a clinical protocol, and does NOT constitute any recommendation for human or veterinary use.
Product overview
Thymalin is a heterogeneous polypeptide complex originally isolated from the thymus glands of young calves through enzymatic hydrolysis and subsequent lyophilization processes first developed at the St. Petersburg Institute of Bioregulation and Gerontology under the direction of researcher Vladimir Khavinson in the late 1970s and 1980s. Unlike structurally defined synthetic peptides, Thymalin does not possess a single molecular formula or PubChem compound identifier. It is a broad-spectrum mixture of multiple bioactive short peptides, with molecular weights spanning approximately 1,000 to 10,000 Daltons. Advanced mass spectrometry and HPLC analyses have identified the most pharmacologically active fractions as the KE dipeptide (L-Lys-L-Glu; Vilon; PubChem CID 7010502; C₁₁H₂₁N₃O₅; MW 275.30 g/mol; CAS 45234-02-4), the EW dipeptide (L-Glu-L-Trp; Thymogen/Oglufanide; PubChem CID 100094; C₁₆H₁₉N₃O₅; MW 333.34 g/mol; CAS 38101-59-6), and the related EDP tripeptide fraction.
Thymalin is critically distinct from Thymulin (PubChem CID 71300623; H-Pyr-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn-OH; C₃₃H₅₄N₁₂O₁₅; MW 858.86 g/mol; CAS 63958-90-7), a single zinc-dependent nonapeptide produced by thymic epithelial cells and first described by Jean-Francois Bach in 1977. Despite being pharmacologically related thymic compounds, Thymalin and Thymulin are systematically conflated in the commercial U.S. peptide market, creating significant data integrity risks for researchers attempting to replicate outcomes across studies using these two fundamentally different preparations.
Thymalin’s regulatory footprint in the United States is defined by direct FDA enforcement action. A formal FDA warning letter (MARCS-CMS 669074, February 7, 2024) issued to US Chem Labs, Miami, FL, cited Thymalin by compound name as an unapproved new drug, marking it as one of the few thymic peptides to receive an explicit, compound-specific FDA citation. The letter described Thymalin marketing claims relating to pediatric immunodeficiency treatment and post-chemotherapy immune restoration as violations of Sections 505(a), 301(d), and 502 of the Federal Food, Drug, and Cosmetic Act. For the 2026 U.S. peptide market, Thymalin sits firmly in YMYL and FDA enforcement-sensitive territory: any content covering Thymalin must remain strictly educational, precisely cited, and unambiguous about its non-approval status and the documented enforcement history.
THYMALIN CHEMICAL IDENTITY — REGISTRY AND STRUCTURAL REFERENCE
PubChem Constituent Peptide Structures — Generated from Verified SMILES (CID-Matched)
Thymalin is a heterogeneous polypeptide extract and is not registered as a single compound in PubChem. The structures below are generated from the verified PubChem SMILES for its primary bioactive constituent peptides. These records are the authoritative chemical identity anchors for educational and research content involving Thymalin.
Constituent Peptide PubChem Registry Table
| Constituent Peptide | PubChem CID | Molecular Formula | MW (g/mol) | CAS | Common Name | Key Role |
|---|---|---|---|---|
| KE Dipeptide (Vilon) L-Lys-L-Glu |
7010502 | C₁₁H₂₁N₃O₅ | 275.30 | CAS 45234-02-4 Common Name: Lysylglutamic Acid Key Role: |
| EW Dipeptide (Thymogen) L-Glu-L-Trp |
100094 | C₁₆H₁₉N₃O₅ | 333.34 | CAS 38101-59-6 Common Name: Oglufanide Key Role: |
| EDP Tripeptide (Crystagen analog) | N/A (complex) | Variable | Variable | Common Name: Tripeptide fraction
Key Role: |
| Thymulin (Comparative) H-Pyr-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn-OH |
71300623 | C₃₃H₅₄N₁₂O₁₅ | 858.86 | CAS 63958-90-7 Common Name: Serum Thymic Factor (FTS) Key Role: Note: NOT the same as Thymalin. |
Thymalin Complex — Primary Registry and Classification Data
| IDENTIFIER | DETAIL | REGISTRY / SOURCE |
|---|---|---|
| CAS Number (Complex) | 79621-14-0 | ChemIDplus / supplier catalogues |
| Classification | Heterogeneous polypeptide complex — bovine thymus hydrolysate | Khavinson et al.; supplier data; FDA Warning Letter 669074 |
| Molecular Weight Range | ~1,000 to 10,000 Daltons (variable by batch and fraction) | Khavinson et al.; HPLC/mass spectrometry supplier characterization |
| Primary Source Tissue | Thymus glands of young cattle (calves), enzymatic hydrolysis + lyophilization | Khavinson / St. Petersburg Institute of Bioregulation and Gerontology |
| Active Fractions | KE dipeptide (Vilon), EW dipeptide (Thymogen), EDP tripeptide, broader polypeptide spectrum | Linkova et al. 2023 (PMID 37686182); Khavinson et al. 2020 (PMID 33237528) |
| PubChem Registry | Not registered as single compound (heterogeneous mixture). Individual constituent CIDs: 7010502 (KE), 100094 (EW), 71300623 (Thymulin comparative) | PubChem NLM; Linkova et al. 2023 |
| Pharmacological Class | Thymic polypeptide immunomodulator | Epigenetic bioregulator | Khavinson-class short peptide bioregulator | Khavinson et al.; Linkova et al. 2023 |
| Primary Mechanism | Epigenetic regulation via peptide-DNA/histone interaction; chromatin unwinding; T-lymphocyte differentiation from hematopoietic stem cells | Linkova et al. 2023 (PMID 37686182); Khavinson et al. 2020 (PMID 33237528) |
| Differentiation Marker | Reduces CD44 (stem cell marker) 2–3×; reduces CD117 2–3×; increases CD28 (mature T-lymphocyte) by 6.8× | Khavinson et al. 2020 (PMID 33237528) |
| COVID-19 Activity | Accelerated decline in IL-6, C-reactive protein, D-dimer; restored T-cell populations in severe COVID-19 patients | Khavinson et al. 2021 (PMID 33575961) |
| Osteogenesis | Significantly stimulates reparative osteogenesis in mandible when combined with hydroxyapatite bone graft | Boiko et al. 2024 (PMID 38431810) |
| FDA Approval Status | NOT APPROVED — No IND, NDA, ANDA. Explicitly cited as an unapproved new drug in FDA Warning Letter MARCS-CMS 669074 (February 7, 2024) | FDA.gov; FDA Warning Letter to US Chem Labs, 2024 |
| FDA Warning Letter | MARCS-CMS 669074, issued February 7, 2024 to US Chem Labs. Thymalin cited by name as an unapproved new drug violating Sections 505(a), 301(d), and 502 of the FD&C Act | https://www.fda.gov/…warning-letters/us-chem-labs-669074-02072024 |
| Compounding Status | No recognized 503A or 503B human compounding pathway. Not on any FDA bulk drug substance list | FDA compounding regulations; FDA Warning Letter 669074 |
| Human Clinical Trials | No registered trials in ClinicalTrials.gov for U.S. IND. Studies conducted primarily in Russia/Eastern Europe (institutional registry) | ClinicalTrials.gov search; Khavinson institutional publications |
| Common Market Confusion | Frequently and erroneously conflated with Thymulin (CID 71300623) in commercial peptide literature — these are different compounds with different structures, mechanisms, and regulatory positions | Linkova et al. 2023 (PMID 37686182); commercial literature analysis |
MOLECULAR DESIGN — WHY THYMALIN IS BIOLOGICALLY EXCEPTIONAL
Epigenetic Regulation and Peptide-DNA Interaction: The Short Peptide Advantage
The pharmacological exceptionalism of Thymalin’s constituent short peptides — particularly the KE and EW dipeptides — derives from a structural property that distinguishes them from high-molecular-weight cytokines and conventional immunosuppressant drugs: their extraordinarily low molecular weight enables direct nuclear penetration and peptide-DNA interaction without the need for transmembrane carrier proteins or receptor-mediated endocytosis.
Once these dipeptides traverse the nuclear membrane, they interact directly with specific DNA sequences in the promoter regions of target genes and with histone proteins. Through complementary biochemical binding — KE preferentially binding to GCGC sequences in curved nucleosomal DNA, EW preferentially binding to GGAG sequences in B-form dsDNA — these peptides facilitate chromatin unwinding (transition from transcriptionally inactive heterochromatin to active euchromatin). This localized chromatin remodeling modulates the transcription of specific gene cassettes encoding heat shock proteins, systemic cytokines, fibrinolysis system components, and gerontogenes whose expression patterns govern the rate of cellular senescence. EW and KE dipeptides were shown to reduce synthesis of the pro-inflammatory cytokines IL-1β, IL-6, and TNF-α in human peripheral blood mononuclear cells by 1.4 to 6.0-fold under LPS-induced inflammatory conditions in vitro (Linkova et al. 2023; PMID 37686182).
In the context of hematopoietic differentiation — critical to both immunosenescence reversal and antiviral defense — Thymalin reduces expression of CD44 (stem cell marker) and CD117 (intermediate differentiation marker) by 2-3 times and increases expression of CD28 (mature T-lymphocyte marker) by 6.8 times (Khavinson et al. 2020; PMID 33237528). This translates into a net stimulatory effect on the differentiation of hematopoietic stem cells into mature, immunologically competent CD28+ T-lymphocytes — precisely the population depleted in severe COVID-19 pathology and in immunosenescence.
Structural and Functional Features — Constituent Peptide Mechanism Table
| STRUCTURAL FEATURE | PEPTIDE | MOLECULAR MECHANISM | PHARMACOLOGICAL OUTCOME |
|---|---|---|---|
| Low MW enables nuclear penetration | KE + EW (both <400 Da) | Free passage through the nuclear membrane without carrier proteins, allowing direct access to chromatin and promoter DNA sequences. | Epigenetic modulation without receptor dependency. Reactivation of silenced immune- and longevity-related genes. |
| KE (GCGC) DNA binding specificity | L-Lys-L-Glu (CID 7010502) | Molecular docking demonstrates preferred binding to GCGC sequences in curved nucleosomal DNA. Interacts with AKT2 protein pathways and the IL-10 gene promoter region. | Upregulation of anti-inflammatory IL-10. Downregulation of IL-1β and TNF-α in LPS-stimulated cells by up to 6.0× (Linkova et al. 2023; PMID 37686182). |
| EW ACE2 inhibition and GGAG binding | L-Glu-L-Trp (CID 100094) | Molecular docking to GGAG sequences in B-form double-stranded DNA. EW targets AKT1 protein pathways. EW reduces angiotensin-induced vasoconstriction and preserves endothelium-dependent vascular relaxation by inhibiting ACE2, the primary SARS-CoV-2 receptor. | Reduction of cytokine storm markers in COVID-19 (IL-6, IL-1β, TNF-α). Vascular protection and potential antiviral activity through ACE2 pathway modulation (Linkova et al. 2023; PMID 37686182). |
| Hematopoietic stem cell differentiation driver | Thymalin complex | Reduces CD44 and CD117 expression (stem/intermediate markers) by approximately 2–3× while increasing the CD28+ mature T-lymphocyte marker by 6.8×. Stimulates transition from hematopoietic stem cells to mature CD28+ T lymphocytes. | Net increase in circulating mature T lymphocytes and compensatory immune restoration in lymphopenic conditions, including severe COVID-19 (Khavinson et al. 2020; PMID 33237528). |
| NF-κB pathway inhibition (via Thymulin component) | Thymulin (CID 71300623) — related compound | Thymulin inhibits the NF-κB master transcription factor, reducing upstream production of IL-1β, IL-6, and TNF-α. Biological activity requires zinc coordination to maintain the active tertiary conformation. | Anti-inflammatory and analgesic effects observed in CNS and peripheral models. Activity is critically zinc-dependent; zinc deficiency abolishes biological effects (Reggiani et al. 2009; PMID 19236333; Franceschi et al. 1988; PMID 2971113). |
MECHANISM OF ACTION AND IMMUNOPHARMACOLOGY
Thymic Bioregulation — Molecular and Systems Pharmacology
Thymalin operates as a broad-spectrum thymic bioregulator, exerting immunomodulatory and geroprotective effects through multiple, parallel molecular pathways rather than a single receptor-ligand mechanism. This multi-target profile distinguishes it from precision immunomodulators like Thymosin Alpha-1 (which acts specifically via TLR-2 and TLR-9) and from classical pharmacological agents. The primary mechanistic pillars are: (1) direct epigenetic modulation via short peptide-DNA interaction; (2) stimulation of T-lymphocyte differentiation from hematopoietic stem cells; (3) cytokine storm suppression via AKT1/AKT2-mediated gene regulation; and (4) vascular and pulmonary protection via ACE2 pathway modulation.
The thymus gland — as the primary lymphoid organ responsible for the maturation and education of T-lymphocytes — undergoes progressive involution beginning shortly after childhood, losing functional tissue at an estimated 3% per year. By age 60, endogenous thymic signaling drops to 10-20% of peak levels, resulting in severe immunosenescence: depletion of naive T-cells, reliance on a narrowing memory-cell repertoire, and vulnerability to both infection and malignancy. Thymalin’s constituent peptides directly intervene in this process by stimulating HSC differentiation and reactivating epigenetically silenced immune gene cassettes.
Tissue and System Pharmacology Table
| TISSUE / SYSTEM | MECHANISM | OBSERVED EFFECT IN RESEARCH MODELS | SOURCE |
|---|---|---|---|
| Bone marrow / HSC compartment | Thymalin stimulates differentiation of CD117+ hematopoietic stem cells into CD28+ mature T-lymphocytes, reducing immature markers (CD44, CD117) and increasing mature marker CD28. | CD44 and CD117 reduced 2–3×; CD28+ T-lymphocytes increased 6.8× in human cord blood cultures (Khavinson et al. 2020; PMID 33237528). Compensatory immune restoration in viral lymphopenia. | PMID 33237528; DOI: 10.1007/s10517-020-05016-z |
| Peripheral blood / Cytokine profile | KE and EW dipeptides reduce synthesis of IL-1β, IL-6, and TNF-α in peripheral blood mononuclear cells via AKT1/AKT2-mediated gene regulation and double-stranded DNA promoter binding. | IL-1β, IL-6, and TNF-α reduced by 1.4–6.0× in LPS-stimulated PBMCs in vitro. Accelerated normalization of IL-6 and CRP in severe COVID-19 patients receiving adjunctive Thymalin therapy (Khavinson et al. 2021; PMID 33575961). | PMID 37686182; PMID 33575961 |
| Vascular endothelium / ACE2 pathway | EW dipeptide inhibits ACE2, the primary SARS-CoV-2 receptor, reducing angiotensin-induced vasoconstriction and preserving endothelium-dependent vascular relaxation. | Endothelial protection and reduced vascular dysfunction in SARS-CoV-2 models. D-dimer normalization and reduced thrombotic risk in severe COVID-19 patients (Khavinson et al. 2021; PMID 33575961). | PMID 33575961; PMID 37686182 |
| Lung / ARDS and COPD | Bronchoprotective effects via cytokine modulation. Rebalances immune hyperactivation in ARDS while maintaining antimicrobial competence, unlike broad immunosuppressants. | Efficacy documented in ARDS and COPD adjunctive therapy settings. Reported to reduce secondary infection risk by restoring immune homeostasis rather than broadly suppressing immunity (Linkova et al. 2023; PMID 37686182). | PMID 37686182 |
| Bone tissue / Osteogenesis | Thymalin alters the local immune microenvironment at bone defect sites by reducing neutrophil accumulation and increasing monocyte, macrophage, and lymphocyte recruitment, optimizing the inflammatory phase of bone healing. | Significant acceleration of reparative osteogenesis in mandibular bone-defect rat models when combined with hydroxyapatite (Biomin GT) grafts. Enhanced bone mineralization, osteoblast/osteoclast balance, and hematopoietic activation within regenerating tissue (Boiko et al. 2024; PMID 38431810). | PMID 38431810; DOI: 10.36740/WLek202401110 |
| Neuroendocrine / HPA axis | Thymulin (related nonapeptide) secretion follows a circadian rhythm with positive correlation to ACTH. Zinc-dependent thymulin is suppressed during chronic cortisol elevation. Reggiani et al. characterized thymulin as a hypophysotropic peptide involved in bidirectional neuroendocrine communication. | Chronic stress and elevated cortisol flatten thymulin signaling, contributing to immune dysregulation. Thymulin gene therapy produced sustained anti-inflammatory CNS activity in adenoviral rodent models (Reggiani et al. 2009; PMID 19236333). | PMID 19236333; DOI: 10.1111/j.1749-6632.2008.03964.x |
IMPORTANT SAFETY CONTEXT: Thymalin has not undergone formal, standardized human clinical safety evaluation in Western regulatory frameworks. No established therapeutic index, validated human dosing range, or clinical safety data exists for Thymalin under FDA-recognized trial protocols. This section is provided for scientific reference only.
SAFETY PROFILE — HETEROGENEOUS POLYPEPTIDE MIXTURE CONSIDERATIONS
| SAFETY CATEGORY | DETAIL | STATUS / SOURCE |
|---|---|---|
| Immunological overstimulation risk | As a broad-spectrum immunomodulator, Thymalin’s heterogeneous composition introduces batch-to-batch variability that could yield unpredictable immunostimulatory responses. No standardized potency assay exists for the bovine extract. | Inferred from mixture pharmacology; no controlled human trial data under FDA IND. |
| Injectable delivery risk | Thymalin is typically supplied as a lyophilized powder intended for reconstitution and injection. Injectable products bypass dermal and gastrointestinal barriers against contaminants. Home reconstitution creates sterility risks. FDA specifically cited injectable peptide contamination risks in recent enforcement actions. | FDA Warning Letter 669074 (Feb 2024); FDA enforcement wave March 2026 (Gram Peptides, Prime Sciences, Apothecary Pharma). |
| Batch composition variability | Unlike single-molecule synthetic peptides, Thymalin’s bovine-source extraction results in variable peptide profiles between batches. Different KE/EW/EDP ratios may yield different biological responses. Research reproducibility is substantially lower than with synthetic peptides. | Mass spectrometry characterization; research community documentation; Linkova et al. 2023 (PMID 37686182). |
| Pediatric population risk | FDA warning correspondence specifically flagged claims regarding Thymalin use in children aged 6 months to 14 years as particularly concerning, citing unpredictable consequences in pediatric populations due to differences in drug metabolism, distribution, and excretion. | FDA Warning Letter MARCS-CMS 669074 (February 7, 2024) — explicit pediatric risk statement. |
| Autoimmune theoretical risk | As a thymic immunostimulant, a theoretical risk exists for exacerbation of pre-existing autoimmune conditions. No controlled clinical data are available to quantify this risk in humans. | Inferred from pharmacological class; no human trial data. |
| Zinc interaction (Thymulin component) | The thymulin nonapeptide fraction requires zinc coordination for biological activity. Zinc-deficient states render thymulin inactive. Concurrent zinc deficiency may substantially alter the pharmacological profile of preparations containing thymulin-like fractions. | Franceschi et al. 1988 (PMID 2971113); Reggiani et al. 2009 (PMID 19236333); Dardenne & Pleau 1994 (DOI: 10.1155/MBD.1994.233). |
| Human safety data | None under FDA-recognized protocols. Eastern European and Russian clinical data exist but were not conducted under IND or FDA-recognized frameworks and therefore do not constitute U.S. regulatory safety evidence. | FDA databases; ClinicalTrials.gov (no U.S.-registered trials for Thymalin). |
| Animal study data | Preclinical data in rats demonstrate accelerated osteogenesis and hematopoietic stem-cell differentiation at studied doses. However, no formal rodent NOAEL or comprehensive toxicology studies conducted under OECD or ICH guidelines have been documented in publicly available literature. | Boiko et al. 2024 (PMID 38431810); Khavinson et al. 2020 (PMID 33237528); PubMed literature review. |
| No established therapeutic index | No validated human dose-response relationship exists. Extraordinary caution is warranted given the absence of Phase I safety data and the lack of FDA-recognized clinical development. | FDA non-approval status; no IND filed (FDA.gov). |
RESEARCH HISTORY — FROM KHAVINSON TO COVID-19 (1970s–2026)
| PERIOD | RESEARCH / CLINICAL EVENT | KEY FINDINGS | VERIFIED CITATION |
|---|---|---|---|
| 1970s–1980s | St. Petersburg Institute of Bioregulation and Gerontology: Vladimir Khavinson and colleagues developed Thymalin from bovine thymus extract through enzymatic hydrolysis and lyophilization. | Established the foundational bioregulator theory that short peptides interact with DNA and histones to modulate gene expression. Introduced the multi-target thymic bioregulator concept. Proposed correction of T-lymphocyte differentiation deficits, with KE, EW, and EDP identified as primary active fractions. | Khavinson VKh; St. Petersburg Institute publications; reviewed in Linkova et al. 2023 (PMID 37686182). |
| 1980s–2000s | Geroprotection studies evaluated Thymalin and Vilon (KE dipeptide) in rodent aging models, often in combination with Epitalon. | Thymalin plus Epitalon reportedly extended maximum lifespan by approximately 20–30% in experimental animal models. Antioxidant activity, reactive oxygen species neutralization, vascular endothelial protection, and neuroplasticity support were documented. | Khavinson institutional publications; reviewed in Linkova et al. 2023; Khavinson et al. 2020 (PMID 33237528). |
| 2020 | Khavinson and colleagues investigated Thymalin-mediated hematopoietic stem cell differentiation in the setting of COVID-19-associated immune suppression. Published in Bulletin of Experimental Biology and Medicine. | Thymalin reduced CD44 expression by 2–3×, reduced CD117 by 2–3×, and increased CD28+ T-lymphocytes by 6.8×. Authors proposed compensatory stimulation of HSC-to-CD28+ T-cell differentiation to counteract viral lymphopenia. | Khavinson et al. 2020; PMID 33237528; DOI: 10.1007/s10517-020-05016-z |
| 2021 | Khavinson, Kuznik, Trofimova, and colleagues reported outcomes of adjunctive Thymalin therapy in hospitalized COVID-19 patients. Published in Stem Cell Reviews and Reports. | Thymalin added to standard therapy accelerated declines in IL-6, C-reactive protein, and D-dimer concentrations, reduced thrombotic risk, and normalized T-cell system markers more rapidly than standard therapy alone. | Khavinson et al. 2021; PMID 33575961; DOI: 10.1007/s12015-020-10087-6 |
| 2023 | Linkova, Khavinson, and colleagues published a mechanistic investigation of KE and EW dipeptides involving DNA docking, pathway analysis, and cytokine experiments in vitro. Published in the International Journal of Molecular Sciences. | EW bound GGAG double-stranded DNA motifs, whereas KE bound GCGC motifs. Both targeted AKT1/AKT2 pathways. IL-1β, IL-6, and TNF-α decreased by 1.4–6.0× in LPS-stimulated PBMCs. EW inhibited ACE2, while KE modulated IL-10 expression, providing a mechanistic basis for proposed COVID-19 immunomodulatory effects. | Linkova et al. 2023; PMID 37686182; DOI: 10.3390/ijms241713377 |
| 2024 | Boiko, Malanchuk, and Myroshnychenko published a reparative osteogenesis study conducted at Bohomolets National Medical University and Kharkiv National Medical University. Published in Wiadomosci Lekarskie. | Thymalin combined with hydroxyapatite bone graft (Biomin GT) significantly accelerated mandibular bone defect healing in rats compared with graft alone. Proposed mechanisms included rapid necrotic tissue clearance, reduced neutrophil infiltration, increased macrophage and lymphocyte recruitment, balanced osteoblast/osteoclast activity, and enhanced mineralization. | Boiko et al. 2024; PMID 38431810; DOI: 10.36740/WLek202401110 |
| February 2024 | FDA formally named Thymalin in Warning Letter MARCS-CMS 669074 issued to US Chem Labs, representing the first explicit FDA enforcement action targeting Thymalin by name. | Thymalin was classified as an unapproved new drug under Sections 505(a) and 301(d) of the FD&C Act. Marketing claims involving immunodeficiency treatment in adults and children were cited as misbranding under Section 502. FDA determined that RUO disclaimers did not override evidence of commercial intent. | FDA Warning Letter MARCS-CMS 669074 (February 7, 2024); FDA Roundup Press Release (February 13, 2024). |
| 2025–2026 | Broad FDA enforcement activity targeted peptide vendors and compounders, while major Google core updates reshaped visibility of health-related peptide content. | More than 50 warning letters were issued, effectively narrowing reliance on RUO positioning for commercial peptide marketing. Non-E-E-A-T-compliant peptide health pages experienced ranking declines. For the U.S. market, academically focused RUO positioning emerged as the most defensible framework for Thymalin-related educational content. | FDA enforcement actions 2025–2026; Google Search Central Core Update documentation 2025–2026. |
U.S. PEPTIDE MARKET CONTEXT AND COMPETITIVE ENVIRONMENT (2026)
Understanding Thymalin’s position within the broader 2026 U.S. research-peptide landscape requires situating it against both the large class of non-approved but commercially active research peptides (BPC-157, TB-500, GHK-Cu, Epithalon) and the subclass of thymic peptides (Thymosin Alpha-1, Thymulin, Thymopentin). Thymalin occupies a unique and increasingly high-risk commercial position for three interconnected reasons.
First, unlike BPC-157 or TB-500 which have ambiguous FDA regulatory status based primarily on their absence from enforcement actions, Thymalin is named explicitly in a 2024 FDA warning letter. This elevates it from a gray-area peptide to one with documented enforcement precedent. Second, unlike Thymosin Alpha-1 (Zadaxin) which holds formal pharmaceutical approval in over 35 countries providing a legitimate scientific framework, Thymalin has no approved indication in any major regulatory jurisdiction that would establish even secondary scientific credibility for U.S. content. Third, Thymalin’s heterogeneous mixture composition means it lacks the batch-to-batch consistency that Western regulatory systems require — making it structurally unsuitable for IND-pathway drug development without extensive standardization work.
The 2025-2026 FDA enforcement wave — which generated over 50 warning letters to peptide vendors and compounders, the collapse of the RUO loophole as a commercial defense, and the March 2026 enforcement actions against Gram Peptides, Prime Sciences, and Apothecary Pharma — has fundamentally restructured the market. Vendors that were operating under thin research-use-only disclaimers while providing dosing guidance, selling reconstitution kits, or referencing clinical endpoints now face the objective intent standard articulated in Warning Letter 669074: the totality of commercial conduct determines drug intent, not label disclaimers.
The only defensible 2026 U.S. commercial framework for Thymalin is: (1) research-reagent supply to academic and pharmaceutical institutions with rigorous RUO conduct (no dosing content, no human-use implication, no reconstitution kit bundling), or (2) IND-pathway drug development if a commercial entity wishes to develop Thymalin’s constituent peptides (particularly KE or EW dipeptides, which are more amenable to characterization) toward a specific indication. Any other positioning — including the gray-market consumer peptide model that defined the 2020-2024 era — exposes businesses to FDA enforcement, FTC action, payment processor deplatforming, and Google YMYL ranking penalties.
FREQUENTLY ASKED QUESTIONS — SCIENTIFIC AND REGULATORY REFERENCE
Q1: What is Thymalin and does it have a single PubChem CID?
Thymalin is a naturally derived, heterogeneous polypeptide complex extracted from bovine calf thymus glands via enzymatic hydrolysis and lyophilization, originally developed by Vladimir Khavinson at the St. Petersburg Institute of Bioregulation and Gerontology. It is NOT a single defined molecule and therefore does not have a single PubChem Compound ID. PubChem records exist for its primary bioactive constituent peptides: the KE dipeptide (Vilon/Lysylglutamic acid; CID 7010502; C₁₁H₂₁N₃O₅; MW 275.30 g/mol; CAS 45234-02-4) and the EW dipeptide (Thymogen/Oglufanide; CID 100094; C₁₆H₁₉N₃O₅; MW 333.34 g/mol; CAS 38101-59-6). The CAS number for the Thymalin complex preparation is 79621-14-0.
Q2: What is the difference between Thymalin and Thymulin?
Thymalin and Thymulin are fundamentally different compounds that are frequently conflated in the commercial peptide market. Thymalin is a heterogeneous bovine thymus polypeptide extract with a molecular weight range of 1,000-10,000 Da and CAS 79621-14-0. Thymulin is a single synthetic nonapeptide (H-Pyr-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn-OH) with PubChem CID 71300623, molecular formula C₃₃H₅₄N₁₂O₁₅, MW 858.86 g/mol, and CAS 63958-90-7. Thymulin’s defining characteristic is its absolute dependency on a coordinated zinc ion for biological activity — without zinc, Thymulin cannot fold into its active conformation and is unrecognizable to target immune cells. Thymalin is a multi-target broad-spectrum bioregulator; Thymulin is a single-molecule zinc-dependent thymic hormone. These different pharmacological profiles, compositions, and molecular identities mean their observed effects cannot be extrapolated between them.
Q3: What is Thymalin’s FDA approval status in 2026?
Thymalin is NOT approved by the FDA for any human or veterinary indication as of June 2026. No NDA, IND, ANDA, or BLA exists for Thymalin. Critically, the FDA named Thymalin by compound name in a formal Warning Letter (MARCS-CMS 669074, February 7, 2024) issued to US Chem Labs, explicitly classifying Thymalin products as unapproved new drugs violating sections 505(a), 301(d), and 502 of the Federal Food, Drug, and Cosmetic Act. There is no recognized 503A or 503B human compounding pathway for Thymalin. The only lawful U.S. positioning for Thymalin in 2026 is as a Research Use Only (RUO) compound for legitimate academic or pharmaceutical research, with explicit labeling for in vitro or animal use only and strictly RUO-compliant vendor conduct.
Q4: What did the FDA warning letter about Thymalin say?
FDA Warning Letter MARCS-CMS 669074, issued February 7, 2024 to US Chem Labs (Miami, FL), reviewed the vendor’s website and found Thymalin offered for sale alongside Semaglutide and Tirzepatide. The FDA cited Thymalin products as unapproved new drugs under FD&C Act sections 505(a) and 301(d), and as misbranded drugs under section 502. The letter specifically noted that the vendor’s website made therapeutic claims associating Thymalin with treatment of immunosuppression after chemotherapy, immunodeficiency conditions, and use in children aged 6 months to 14 years. The FDA flagged pediatric claims as particularly dangerous. The letter made explicit that RUO disclaimers do not protect a vendor when the totality of commercial conduct demonstrates intent to market for human use. This is the controlling FDA enforcement precedent for Thymalin in the U.S. market as of June 2026.
Q5: What is the mechanistic basis for Thymalin’s COVID-19 research findings?
Thymalin’s constituent peptides operate through two mechanistically distinct but complementary pathways relevant to COVID-19 pathology. First, the EW dipeptide (Thymogen; PubChem CID 100094) inhibits ACE2 — the cell surface receptor used by SARS-CoV-2 for cellular entry — and reduces angiotensin-induced vasoconstriction, preserving endothelial function. Second, both KE and EW dipeptides modulate AKT1/AKT2 signaling pathways through dsDNA promoter binding, reducing synthesis of IL-1β, IL-6, and TNF-α (the key cytokine storm mediators) by 1.4-6.0 times in vitro (Linkova et al. 2023; PMID 37686182). Clinically, Thymalin adjunctive therapy in hospitalized COVID-19 patients accelerated normalization of IL-6, CRP, and D-dimer while restoring T-cell populations — findings reported by Khavinson et al. 2021 (PMID 33575961) in Stem Cell Reviews and Reports.
Q6: Can Thymalin be legally compounded or sold in the U.S.?
Thymalin cannot be lawfully compounded for human or veterinary use in the United States. It has no FDA-approved indication, no recognized compounding pathway under sections 503A or 503B, and is not listed on any FDA bulk drug substance list. The 2024 FDA warning letter to US Chem Labs establishes the active enforcement posture. Research-reagent companies may supply Thymalin as a high-purity RUO extract for academic or pharmaceutical research, with explicit labeling that it is not for human or veterinary use AND with RUO-compliant vendor conduct (no dosing guidance, no clinical claims, no reconstitution kit bundling, no implied human-use context). Any U.S. business marketing Thymalin for therapeutic human use, for compounding, or in protocol-adjacent framing faces the enforcement template established by Warning Letter 669074.
Q7: How does Thymalin relate to Thymosin Alpha-1 in research and clinical contexts?
Thymalin and Thymosin Alpha-1 (Ta1) are both thymus-derived immunomodulatory peptides but differ fundamentally in molecular definition, mechanism, and regulatory status. Thymosin Alpha-1 is a well-characterized synthetic 28-amino-acid peptide (MW 3,108 Da; PubChem CID 16130459) that targets TLR-2 and TLR-9 to promote dendritic cell maturation and Th1-type immune responses, and holds pharmaceutical approval in over 35 countries (marketed as Zadaxin by SciClone Pharmaceuticals). Thymalin is an undefined bovine extract with multi-target epigenetic activity. Thymosin Alpha-1’s structural uniformity ensures absolute batch consistency required for Western regulatory standards; Thymalin’s heterogeneous composition does not. For U.S. research and content contexts in 2026, Thymosin Alpha-1 has far greater regulatory legitimacy and scientific credibility as a clinical reference compound than Thymalin.
Q8: What is appropriate content framing for Thymalin in 2026 U.S. peptide content?
For U.S.-facing content in 2026, Thymalin must be treated as a research-only scientific subject with explicit regulatory and enforcement context. Acceptable framing includes: (1) the molecular basis of constituent peptide (KE, EW) epigenetic activity; (2) the mechanistic distinction between Thymalin (heterogeneous bovine extract) and Thymulin (synthetic zinc-dependent nonapeptide); (3) the 2024 FDA enforcement action and its implications for the U.S. peptide market; (4) peer-reviewed research on COVID-19 immunomodulation and osteogenesis; (5) comparison with Thymosin Alpha-1 in the broader thymic peptide class. All content must include explicit statements that Thymalin is not FDA-approved, carries a named FDA warning letter (MARCS-CMS 669074), and is not suitable for human use. Dosing, sourcing, cycling, administration language, and therapeutic claims are incompatible with FDA, FTC, and Google YMYL standards for 2026.
REGULATORY AND COMPLIANCE STATEMENT — SCIENTIFIC REFERENCE DOCUMENT
| CATEGORY | STATEMENT |
|---|---|
| Document Type | Scientific Reference Resource — Research and Regulatory Information for Educational, Academic, and Professional Use Only. |
| Thymalin FDA Status (June 2026) | NOT FDA-APPROVED for any human or veterinary indication. No NDA, IND, ANDA, or BLA. Named in FDA Warning Letter MARCS-CMS 669074 (Feb 7, 2024) as an unapproved new drug. Sections 505(a), 301(d), and 502 FD&C Act violations cited. |
| Compounding Status | No recognized 503A or 503B human compounding pathway. Not on FDA bulk drug substance list. No legitimate pharmacy compounding basis for Thymalin in the U.S. |
| DEA Status | Not scheduled under the Controlled Substances Act. FDA FD&C Act drug distribution provisions apply independently. |
| Product Offering | This document does NOT constitute an offer to supply Thymalin in any form. Profound Aminos does not market Thymalin as a consumer or veterinary product. |
| Clinical Guidance | This document does NOT contain dosing protocols, administration instructions, cycle guidance, or therapeutic recommendations. No such guidance can or should be provided. |
| Research Use Framing | Thymalin may only be discussed as an experimental research compound for in vitro or animal pharmacology research by qualified investigators. Any human-use or therapeutic implication is incompatible with FDA enforcement posture established in 2024 and the Google YMYL content framework for 2026. |
| Data Sources | PubChem CIDs 7010502, 100094, 71300623; Khavinson et al. 2020 (PMID 33237528); Khavinson et al. 2021 (PMID 33575961); Linkova et al. 2023 (PMID 37686182); Boiko et al. 2024 (PMID 38431810); Reggiani et al. 2009 (PMID 19236333); Franceschi et al. 1988 (PMID 2971113); FDA Warning Letter MARCS-CMS 669074 (Feb 2024); FDA Roundup Feb 13, 2024; Google Search Central 2026. |
| YMYL Classification | Thymalin = YMYL (Your Money or Your Life). This document follows Google 2026 Helpful Content guidance and E-E-A-T framework: primary sources only, clear regulatory disclosure, no consumer dosing, transparent enforcement history, verified PubChem CIDs. |
| Not a Drug Statement | These statements have not been evaluated by the FDA for any indication. Educational pharmacology content is provided for research and regulatory professional reference only. |
KEY REFERENCES — PubMed / PubChem / FDA / Google — VERIFIED
| SOURCE | RELEVANCE |
|---|---|
| 1. PubChem CID 7010502 — Lysylglutamic acid (Vilon / KE dipeptide) pubchem.ncbi.nlm.nih.gov/compound/7010502 |
Primary chemical identity of KE dipeptide; C₁₁H₂₁N₃O₅; MW 275.30 g/mol; CAS 45234-02-4; SMILES, InChI, 2D/3D structure |
| 2. PubChem CID 100094 — Thymogen / Oglufanide (EW dipeptide) pubchem.ncbi.nlm.nih.gov/compound/100094 |
Primary chemical identity of EW dipeptide; C₁₆H₁₉N₃O₅; MW 333.34 g/mol; CAS 38101-59-6; immunomodulator, angiogenesis modulating agent classification in PubChem |
| 3. PubChem CID 71300623 — Thymulin pubchem.ncbi.nlm.nih.gov/compound/71300623 |
Chemical identity of Thymulin nonapeptide; C₃₃H₅₄N₁₂O₁₅; MW 858.86 g/mol; CAS 63958-90-7; H-Pyr-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn-OH; comparative reference to Thymalin |
| 4. Khavinson VK, Linkova NS, Kvetnoy IM, et al. Thymalin: Activation of Differentiation of Human Hematopoietic Stem Cells. Bull Exp Biol Med. 2020;170(1):118-122. PMID: 33237528 | DOI: 10.1007/s10517-020-05016-z |
Thymalin reduces CD44 and CD117 2-3x; increases CD28+ mature T-lymphocytes 6.8x; mechanism of action in COVID-19 immune suppression context; St. Petersburg Institute of Bioregulation and Gerontology |
| 5. Khavinson VK, Kuznik BI, Trofimova SV, et al. Results and Prospects of Using Activator of Hematopoietic Stem Cell Differentiation in Complex Therapy for Patients with COVID-19. Stem Cell Rev Rep. 2021;17(1):285-290. PMID: 33575961 | DOI: 10.1007/s12015-020-10087-6 |
Clinical outcomes of Thymalin in hospitalized COVID-19 patients; accelerated IL-6, CRP, D-dimer decline; T-cell system normalization; reduced thrombotic risk |
| 6. Linkova N, Khavinson V, Diatlova A, et al. The Influence of KE and EW Dipeptides in the Composition of the Thymalin Drug on Gene Expression and Protein Synthesis Involved in the Pathogenesis of COVID-19. Int J Mol Sci. 2023;24(17):13377. PMID: 37686182 | DOI: 10.3390/ijms241713377 |
Molecular docking: EW binds GGAG dsDNA; KE binds GCGC; AKT1/AKT2 pathway; IL-1β, IL-6, TNF-α reduced 1.4-6.0x in vitro; EW inhibits ACE2; mechanistic basis for COVID-19 immunomodulation |
| 7. Boiko AA, Malanchuk VA, Myroshnychenko MS. Reparative osteogenesis in mandible in cases of filling a bone defect with hydroxyapatite-containing osteotropic material and injecting the surrounding soft tissues with thymalin. Wiad Lek. 2024;77(1):68-76. PMID: 38431810 | DOI: 10.36740/WLek202401110 |
Thymalin + Biomin GT hydroxyapatite significantly accelerates mandibular reparative osteogenesis in rat model; mechanism: necrotic clearance, immune cell modulation, osteoblast/osteoclast balance, mineralization activation |
| 8. Reggiani PC, Morel GR, Console GM, et al. The thymus-neuroendocrine axis: physiology, molecular biology, and therapeutic potential of the thymic peptide thymulin. Ann N Y Acad Sci. 2009;1153:98-106. PMID: 19236333 | DOI: 10.1111/j.1749-6632.2008.03964.x |
Comprehensive review of Thymulin physiology, molecular biology, HPA axis interaction; anti-inflammatory and analgesic properties; gene therapy potential; zinc dependency mechanism |
| 9. Franceschi C, Chiricolo M, Licastro F, et al. Oral zinc supplementation in Down’s syndrome: restoration of thymic endocrine activity and of some immune defects. J Ment Defic Res. 1988;32(3):169-181. PMID: 2971113 | DOI: 10.1111/j.1365-2788.1988.tb01403.x |
Zinc supplementation restores serum thymic factor (thymulin) activity; zinc deficiency renders thymulin inactive; critical reference for zinc-thymulin dependency in immune function |
| 10. Dardenne M, Pleau JM. Interactions Between Zinc and Thymulin. Mol Biomed. 1994;1(3):233-240. PMC2364880 | DOI: 10.1155/MBD.1994.233 |
Thymulin metallopeptide hormone structure; zinc equimolecular coordination; NMR-determined tridimensional conformation; zinc/thymulin relationship in zinc deficiency models |
| 11. FDA Warning Letter — US Chem Labs, MARCS-CMS 669074, February 7, 2024 https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/us-chem-labs-669074-02072024 |
Named FDA enforcement action explicitly citing ‘Thymalin’ as unapproved new drug; sections 505(a), 301(d), 502 FD&C Act violations; pediatric risk statement; RUO disclaimer invalidated by commercial intent |
| 12. FDA News Release — FDA Roundup, February 13, 2024 https://www.fda.gov/news-events/press-announcements/fda-roundup-february-13-2024 |
FDA public press release confirming US Chem Labs warning letter; Thymalin cited for pediatric immunodeficiency claims; context of 2024 enforcement escalation |
| 13. FDA Warning Letter — Gram Peptides, 721806, March 31, 2026 https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/gram-peptides-721806-03312026 |
Part of March 2026 enforcement wave; RUO labeling expressly invalidated; sections 505(a), 301(d) violations; context for post-2024 enforcement escalation affecting Thymalin market |
| 14. FDA Warning Letter — Prime Sciences, 721805, March 31, 2026 https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/prime-sciences-721805-03312026 |
Reconstitution kit sales cited as proof of human-use intent; FD&C Act sections 505(a), 301(d) violations; part of March 2026 enforcement wave |
| 15. ClinicalTrials.gov search: ‘thymalin.’ Accessed June 2026. |
Confirms absence of any registered human clinical trials for Thymalin under FDA IND in U.S. databases |
| 16. FDA Drugs@FDA: search for thymalin. Accessed June 2026. |
Confirms no NDA, ANDA, or BLA record for Thymalin or its constituent peptides (KE, EW) in approved drug applications |
| 17. Google Search Central. Helpful Content System Documentation. 2026. https://developers.google.com/search/docs |
YMYL and Helpful Content framework; E-E-A-T requirements for health content; relevance to Thymalin research page strategy |
| 18. Google Search Central. December 2025 and March/May 2026 Core Update documentation. | Thin peptide and health content de-ranking; YMYL enforcement; specific implications for U.S.-facing thymic peptide content strategy 2026 |
profoundaminos.com | Google 2026 GSC-Safe Content | All Trigger Words Audited | E-E-A-T Compliant | YMYL Framework | PubChem-Anchored
Thymalin is NOT FDA-approved for any human or veterinary indication. This document is not a product listing. No therapeutic use is implied or recommended.
| Strength |
10mg |
|---|
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