Thymosin Alpha-1 vs Thymosin Beta-4
Research Comparison

Research Overview

Thymosin alpha-1 vs thymosin beta-4 compares two peptides that share a name and a source, but not a gene. Both were isolated from thymosin fraction 5, a calf thymus extract. The 1977 paper that sequenced thymosin alpha-1 described a heat-stable, highly acidic 28-residue peptide and proposed a nomenclature for the fraction's polypeptides (Goldstein et al., 1977). Thymosin beta-4 was sequenced in 1981 as a 43-residue peptide with an acetylated N-terminus, then described as a thymic hormone acting on thymocytes (Low et al., 1981).

Later work took the family resemblance apart. A 2012 structural report describes the thymosins as present in many tissues beyond the thymus, unrelated to each other in a genetic sense and apparently different in function within the cell, with thymosin alpha-1 cut from a larger precursor, prothymosin (Volk et al., 2012). Disguised Alpha supplies Thymosin Alpha-1 (5MG or 10MG) and TB-500 (Thymosin Beta-4), labeled 10mg, as lyophilized powders for laboratory research use only.

Structure and Class

Thymosin alpha-1 is not encoded on its own. UniProt places it at residues 2 to 29 of prothymosin alpha (P06454), a 111-residue nuclear protein from the PTMA gene on chromosome 2. Sequence: Ac-SDAAVDTSSEITTKDLKEKKEVVEEAEN. Product page identity: C129H215N33O55, 3108.31 g/mol, matching PubChem CID 16130571, titled thymalfasin, the generic drug name (Volk et al., 2012).

Thymosin beta-4 has its own gene, TMSB4X on the X chromosome (UniProt P62328), and is a 43-residue chain once the initiator methionine is removed: Ac-SDKPDMAEIEKFDKSKLKKTETQEKNPLPSKETIEQEKQAGES. The 1981 paper reported an isoelectric point of 5.1 and a molecular weight of 4982 (Low et al., 1981); the product page lists C212H350N56O78S and 4963 g/mol, matching PubChem CID 16132341 (timbetasin).

Both chains open with an acetylated serine and an aspartate, then diverge; thymosin beta-4 is 15 residues longer and about 1.6 times heavier.

The catalog lists thymosin beta-4 as TB-500 (Thymosin Beta-4), with the full protein's formula and weight; what the TB-500 name covers is answered in our TB-500 vs thymosin beta-4 comparison. Identify any lot by the identity printed on its certificate.

Side by Side

Research Context: Thymosin Alpha-1

Much of the mechanistic work on thymosin alpha-1 uses immune cells. In dendritic cells exposed to the fungus Aspergillus fumigatus, it induced maturation and interleukin-12 production by signaling through MyD88 and distinct Toll-like receptors; in mice, the synthetic peptide activated T helper 1 antifungal responses (Romani et al., 2004). Models: dendritic cell culture and mice.

Its human record is the larger of the two. A double-blind, placebo-controlled phase 3 trial at 22 centers in China randomized 1106 adults with sepsis: 28-day all-cause mortality was 23.4% with thymosin alpha-1 and 24.1% with placebo, and no secondary or safety outcome differed significantly (Wu et al., 2025). Model: adults with sepsis.

Its commercial licensee, holding rights outside the US and Europe, reported approvals in more than 30 countries by 2007 (Tuthill, 2007). Drugs@FDA lists no thymalfasin product (openFDA search, October 2026), and an FDA page on bulk drug substances that may present significant safety risks lists thymosin alpha-1 among withdrawn nominations formerly in category 2, citing possible immunogenicity and impurities. Our material is a research chemical, not that medicine.

Research Context: Thymosin Beta-4

Thymosin beta-4's best-characterized activity is holding actin. In 1991 it proved identical to Fx, the peptide holding most unpolymerized actin in resting human platelets: it forms a one-to-one complex with actin monomers and blocks their polymerization, and its wide distribution pointed to a general role in actin regulation (Safer et al., 1991). Models: human platelets and purified actin.

Thymosin beta-4 also promoted myocardial and endothelial cell migration in the embryonic heart, raised cardiomyocyte survival in culture and formed a complex with PINCH and integrin-linked kinase that activates Akt; after coronary artery ligation in mice, the study reported greater early myocyte survival and better cardiac function (Bock-Marquette et al., 2004). Models: embryonic heart tissue, cultured cardiomyocytes and mice.

In the one phase 3 report for the full protein we found in PubMed, 18 participants with neurotrophic keratopathy were randomized to thymosin beta-4 or placebo eye drops: the corneal epithelial defect closed completely by week 4 in 6 of 10 against 1 of 8 (p = 0.0656, not significant), with a significant difference at day 43; employees of the developer co-designed the study (Sosne et al., 2022). ClinicalTrials.gov lists other phase 3 eye-drop studies. Drugs@FDA lists no thymosin beta-4 product, and the FDA bulk substances page names only its LKKTETQ fragment, also known as TB-500.

Choosing Between Them for a Research Question

Start from the endpoint. Dendritic cell maturation, Toll-like receptor signaling or T helper responses point to thymosin alpha-1; actin sequestration, cell migration, the integrin-linked kinase pathway, or cardiac and corneal epithelial models point to thymosin beta-4. Because prothymosin alpha carries the same 28 residues at its N-terminus, check whether an assay measured the peptide or its precursor.

Head-to-head data depend on the assay. In the human mixed lymphocyte reaction, thymosin alpha-1 enhanced proliferation through T4+ helper cells, while thymosin beta-4 suppressed it through T8+ cells (Baxevanis et al., 1987). In human non-small cell lung cancer lines, thymosin alpha-1 cut colony numbers more potently than thymosin beta-4, and in nude mice only thymosin alpha-1 significantly inhibited xenograft formation (Moody et al., 1993). In the chick chorioallantoic membrane, both enhanced angiogenesis (Koutrafouri et al., 2001). Neither, then, works as an inert control for the other.

Plan arms in moles: one milligram holds about 0.32 µmol of thymosin alpha-1 and about 0.20 µmol of full-length thymosin beta-4, so 10 mg of each differs by about 1.2 µmol. Use the molecular weight and measured content on each lot's certificate.

Handling and Storage

Both ship lyophilized, and both product pages list -20°C for the powder as shipped and 2 to 8°C after reconstitution, protected from light, with freeze/thaw cycles avoided. Let each sealed vial reach room temperature before opening, add diluent slowly down the wall, swirl rather than shake, and split stock into single-use aliquots labeled with the lot number.

Thymosin beta-4's methionine 6 can oxidize, adding 16 mass units; thymosin alpha-1 has no methionine or cysteine. Thymosin alpha-1 is unstructured in water and turns helical in trifluoroethanol or lipid vesicles, with similar behavior discussed for thymosin beta-4 (Volk et al., 2012), so keep buffer, pH and additives identical when both run in one assay. Use the measured content from the COA portal, not the label mass.

Questions Researchers Ask

Thymosin alpha 1 vs thymosin beta 4: what is the difference?

They are unrelated peptides named for a shared source, thymosin fraction 5. Thymosin alpha-1 is a highly acidic 28-residue peptide (Goldstein et al., 1977) cut from prothymosin alpha (Volk et al., 2012); thymosin beta-4 is a 43-residue peptide (Low et al., 1981) that binds actin monomers one to one (Safer et al., 1991).

Thymosin alpha 1 vs TB500: are they related?

Not by sequence or gene. TB-500 is a research name tied to thymosin beta-4, which Disguised Alpha lists as TB-500 (Thymosin Beta-4), so the answer above applies. Whether a TB-500 lot is the full protein or a fragment is covered in the TB-500 vs thymosin beta-4 comparison and the TB-500 research guide.

TA1 vs TB4: has any study tested them side by side?

A few cell and animal studies, with mixed direction: thymosin alpha-1 enhanced the human mixed lymphocyte reaction while thymosin beta-4 suppressed it (Baxevanis et al., 1987), yet both enhanced chick chorioallantoic membrane angiogenesis (Koutrafouri et al., 2001). We found no clinical trial testing both (PubMed and ClinicalTrials.gov, October 2026).

Which one has more human research?

Thymosin alpha-1: a 1106-adult phase 3 sepsis trial that found no mortality difference (Wu et al., 2025) and, as thymalfasin, approvals in more than 30 countries reported by its licensee, whose rights excluded the US and Europe (Tuthill, 2007). The full-length thymosin beta-4 phase 3 report we found covers 18 participants (Sosne et al., 2022). Neither is in Drugs@FDA.

Are thymosin alpha-1 and thymosin beta-4 prohibited in sport?

Thymosin beta-4 is. The 2026 WADA Prohibited List names "Thymosin-β4 and its derivatives e.g. TB-500" under S2.3, growth factors and growth factor modulators, in class S2, which is prohibited at all times. Thymosin alpha-1 is not named on the list.