What is thymosin alpha-1?
Thymosin alpha-1 (also written thymosin alpha 1, Tα-1 or TA1 peptide, and named thymalfasin as a pharmaceutical substance) is a 28-residue, N-terminally acetylated peptide first isolated from calf thymus tissue and sequenced in 1977 (Goldstein et al., 1977). It is one component of the mixture historically called thymosin fraction 5, and the chemical and biological characterisation of that fraction placed the peptide among its more active constituents in the assays used at the time (Low et al., 1979).
Thymalfasin is approved as a medicine in a number of countries outside the United States, where it has been registered since the 1990s by its commercial licensee, while remaining unapproved in the United States and Europe (Tuthill, 2007). The material Disguised Alpha supplies is not that medicine: it is a lyophilized powder sold for laboratory research use only, not for people. Nothing on this page is guidance for use in people.
Thymosin alpha-1 reference data
| Property | Value |
|---|---|
| Name | Thymosin Alpha-1 (Tα-1) |
| Aliases | Thymalfasin, thymosin alpha 1, TA1 peptide, alpha1-thymosin (PubChem CID 16130571) |
| Sequence | 28 amino acid residues with an acetylated N-terminal serine, reported in full by Goldstein et al., 1977 |
| Peptide class | 28-residue thymic peptide |
| Molecular formula | C₁₂₉H₂₁₅N₃₃O₅₅ |
| Molecular weight | 3108.31 g/mol (PubChem lists 3108.3 g/mol for CID 16130571) |
| CAS number | 62304-98-7 (product page and PubChem CID 16130571) |
| Form | Lyophilized powder |
| Sizes carried | 5MG, 10MG |
| Testing | Third-party tested, with the certificate for each lot published on the product page and in the COA portal |
Formula, molecular weight, CAS number, peptide class and sizes are from the Compound Information section of the product page; aliases and the PubChem weight are from PubChem CID 16130571, which agrees on formula and CAS number. Confirm identity and measured content against your lot's certificate.
What the research covers
A PubMed search across the name variants returns roughly 960 records, about 100 of them typed as clinical trials, so this is a far larger literature than most research peptides carry. Published work falls into five areas, and each summary below states the model used.
Identity, origin and the precursor protein
The original isolation work used acid extraction of calf thymus and reported a heat-stable, highly acidic 28-residue peptide (Goldstein et al., 1977; Low et al., 1979). Later work in rat thymus complicated that picture: using an antibody raised against the synthetic peptide, a polypeptide of about 112 residues carrying the same sequence at its N-terminus was isolated and named prothymosin alpha, was the major cross-reacting species in rat thymus extracts, and was proposed as the source from which the 28-residue peptide is generated during isolation of fraction 5 (Haritos et al., 1984).
A later study combining chromatography with immunoassay reported the 28-residue peptide, not the precursor, as the predominant immunoreactive species in serum and thymus (Naylor et al., 1992). Check which species an assay actually measured before comparing papers.
Conformation and membrane interaction
Structural studies agree that the peptide is unstructured in water. In the presence of sodium dodecyl sulfate micelles it adopts a helical fold with a structural break around residues 9 and 14, and paramagnetic relaxation measurements placed residues 1 to 5 inside the hydrophobic region of the micelle (Nepravishta et al., 2015).
A review of the same programme reported that interaction was preferred where the surface carried negative charge, including vesicles containing phosphatidylserine and cultured K562 cells exposing it after induced apoptosis (Nepravishta et al., 2016), and separate work indicated a preliminary interaction with hyaluronan around the C-terminal LKEKK lysines (Mandaliti et al., 2017). A survey of thymosin structures places all of these peptides in the intrinsically unstructured class, with structure inducible by charge neutralisation, metal ions, organic cosolvents or binding partners (Hoch and Volk, 2016). No receptor for the peptide has been established.
Dendritic cell and innate signaling studies
A series of papers from a group in Perugia examined the peptide in mouse and human dendritic cell culture and in mouse infection models. In fungus-pulsed dendritic cells it was reported to induce maturation markers and interleukin-12 production through a p38 MAPK and NF-kB dependent pathway requiring MyD88, with corresponding T helper cell responses in mice challenged with Aspergillus fumigatus (Romani et al., 2004).
A follow-up reported that the same signaling also activated indoleamine 2,3-dioxygenase in murine dendritic cells, with interleukin-10 production and regulatory T cell generation, which the authors read as a simultaneous push toward response and tolerance (Romani et al., 2006). In mice infected with murine cytomegalovirus, effects were reported to depend on TLR9, MyD88 and interferon regulatory factor 7, and were absent in the corresponding deficient strains (Bozza et al., 2007; reviewed in Romani et al., 2007).
Tumor cell culture and xenograft models
In human non-small cell lung cancer lines, the peptide increased the rate of arachidonic acid release and reduced colony number in clonogenic assays at 10⁻⁶ M, while its N-terminal and C-terminal fragments and thymosin beta-4 were less active. In nude mice carrying xenografts of the same lines, the full-length peptide reduced xenograft formation and the fragments did not (Moody et al., 1993). This is cell-culture and mouse work, not a human cancer finding.
Human clinical literature, including a negative phase 3 result
Two randomized studies in adults with sepsis bracket this literature. A six-centre single-blind study in China enrolled 361 patients and reported 28-day mortality of 26.0 percent against 35.0 percent in controls, marginal on the non-stratified analysis (p = 0.062) and conventionally significant only on the log-rank test (p = 0.049), alongside greater improvement in monocyte HLA-DR expression on days 3 and 7 (Wu et al., 2013).
The follow-up was a 22-centre double-blinded placebo-controlled phase 3 trial in 1106 adults: 28-day all-cause mortality was 23.4 percent against 24.1 percent, hazard ratio 0.99 (95 percent confidence interval 0.77 to 1.27, p = 0.93), with no secondary or safety outcome separating the groups and only exploratory subgroup signals by age and diabetes status (Wu et al., 2025). Reviews written before that trial listed many proposed clinical applications (Goldstein and Goldstein, 2009); the 2025 result is the strongest evidence in the field and it was null for its primary endpoint.
Key studies
- Goldstein AL, et al. "Thymosin alpha1: isolation and sequence analysis of an immunologically active thymic polypeptide." Proc Natl Acad Sci U S A. 1977. PMID 265536. DOI 10.1073/pnas.74.2.725. Protein chemistry: isolation and the full 28-residue sequence.
- Low TL, et al. "The chemistry and biology of thymosin. I. Isolation, characterization, and biological activities of thymosin alpha1 and polypeptide beta1 from calf thymus." J Biol Chem. 1979. PMID 216684. Protein chemistry plus bioassays of fraction 5 components.
- Low TL, et al. "Complete amino acid sequence of bovine thymosin beta 4." Proc Natl Acad Sci U S A. 1981. PMID 6940133. DOI 10.1073/pnas.78.2.1162. The 43-residue beta-4 peptide, often confused with this one.
- Haritos AA, et al. "Prothymosin alpha: isolation and properties of the major immunoreactive form of thymosin alpha 1 in rat thymus." Proc Natl Acad Sci U S A. 1984. PMID 6583693. DOI 10.1073/pnas.81.4.1008. Rat thymus extracts: the 112-residue precursor.
- Moody TW, et al. "Thymosin alpha 1 down-regulates the growth of human non-small cell lung cancer cells in vitro and in vivo." Cancer Res. 1993. PMID 8221658. Human lung cancer cell culture plus nude mouse xenografts.
- Romani L, et al. "Thymosin alpha 1 activates dendritic cells for antifungal Th1 resistance through toll-like receptor signaling." Blood. 2004. PMID 14982877. DOI 10.1182/blood-2003-11-4036. Dendritic cell culture plus a mouse fungal model.
- Romani L, et al. "Thymosin alpha1 activates dendritic cell tryptophan catabolism and establishes a regulatory environment for balance of inflammation and tolerance." Blood. 2006. PMID 16741252. DOI 10.1182/blood-2006-02-004762. Murine dendritic cell transfers: indoleamine 2,3-dioxygenase and regulatory T cells.
- Bozza S, et al. "Thymosin alpha1 activates the TLR9/MyD88/IRF7-dependent murine cytomegalovirus sensing for induction of anti-viral responses in vivo." Int Immunol. 2007. PMID 17804687. DOI 10.1093/intimm/dxm097. Mouse infection model, including receptor-deficient strains.
- Nepravishta R, et al. "Thymosin α1 inserts N terminus into model membranes assuming a helical conformation." Expert Opin Biol Ther. 2015. PMID 25642593. DOI 10.1517/14712598.2015.1009034. Structural chemistry in micelles.
- Wu J, et al. "The efficacy and safety of thymosin α1 for sepsis (TESTS): multicentre, double blinded, randomised, placebo controlled, phase 3 trial." BMJ. 2025. PMID 39814420. DOI 10.1136/bmj-2024-082583. Human clinical trial, 1106 adults: null for 28-day all-cause mortality.
Handling and storage of lyophilized thymosin alpha-1
General laboratory practice for this material:
- Store the lyophilized powder at -20°C, protected from light, until use (storage guidance on the product page), and let the sealed vial reach room temperature before opening so moisture does not condense on the powder.
- The peptide is highly acidic, with an unusually high content of glutamic and aspartic acid residues (Goldstein et al., 1977), and is water soluble; prepare stock solutions in water or a neutral buffer and record the pH you used.
- It is unstructured in aqueous buffer and folds only at charged interfaces or in cosolvents such as trifluoroethanol or detergent micelles (Nepravishta et al., 2015; Hoch and Volk, 2016), so hold buffer and detergent composition constant across comparisons if conformation matters to your assay.
- Both the 28-residue peptide and its precursor have been reported to run far larger than their calculated mass on gel filtration, apparently as oligomers (Haritos et al., 1984), so size-based methods can mislead on identity.
- After reconstitution, keep solutions at 2 to 8°C and protected from light, and split stock into single-use aliquots to avoid freeze/thaw cycles.
- Record the lot number and keep its certificate with your notes, and use its measured content rather than the label mass.
Frequently asked questions
What is thymosin alpha-1?
A 28-residue acetylated peptide isolated from calf thymus and sequenced in 1977 (Goldstein et al., 1977). Published work spans protein chemistry, structural studies in model membranes, dendritic cell culture, mouse infection and tumor models, and human clinical trials.
Is thymosin alpha-1 the same thing as thymalfasin?
Thymalfasin is the pharmaceutical name for the synthetic version of the same sequence, and PubChem files both names under CID 16130571. The regulatory status of that medicine is stated above; the material on this page is a research chemical, not that medicine, and not for use in people.
How is it different from thymosin beta-4 or TB-500?
They are unrelated molecules that share the thymosin name because both were found in the same calf thymus fraction. Thymosin beta-4 is 43 residues, about 4982 g/mol, and was sequenced separately (Low et al., 1981). Our TB-500 research guide covers that peptide.
What did the large sepsis trials report?
The 361-patient single-blind study reported a mortality difference that was marginal on its primary analysis (Wu et al., 2013). The 1106-patient phase 3 trial that followed found no difference in 28-day all-cause mortality, 23.4 percent against 24.1 percent (Wu et al., 2025). Any summary citing only the 2013 study is out of date.
Is there a known receptor?
None has been established. The structural literature reports folding and insertion at negatively charged membrane surfaces and proposes that the folded peptide then interacts with nearby proteins, which those authors present as a model rather than an identified target (Nepravishta et al., 2015; Nepravishta et al., 2016).
How should thymosin alpha-1 powder be stored?
Keep the lyophilized powder at -20°C and protected from light. After reconstitution, store the solution at 2 to 8°C, protected from light, and avoid freeze/thaw cycles, as listed on the product page.
Where can researchers buy thymosin alpha-1?
Disguised Alpha sells it for laboratory research, third-party tested with the certificate published on the product page: Thymosin Alpha-1 (5MG and 10MG).
Related compounds and guides
- TB-500 (thymosin beta-4): the 43-residue beta thymosin, a different molecule
- TB-500 research guide
- Thymalin: a thymic peptide preparation, not a single defined peptide
- Thymalin research guide
- Epitalon and its research guide
- COA portal: every published certificate, by lot
This product is for research use only. It has not been evaluated for safety or effectiveness in humans. Not for human consumption. All products are intended for laboratory research purposes only.