Thymosin Alpha-1

Both vials hold the same molecule, so this is a logistics choice. Each size is its own batch with its own certificate: the 5mg batch is UKPL-9508. At the same fill volume the 5mg vial gives half the concentration, so scale volumes instead of carrying them over. The 10mg vial costs less per milligram and puts twice the work under one batch. The 5mg vial costs less up front, is used up sooner once reconstituted, and leaves less spare material if a design changes. A large study run on 5mg vials spans more batches, so track batch numbers across the dataset.

Thymosin alpha-1, also written thymosin α1 or TA1, and known by its INN thymalfasin, is a 28-residue peptide with an acetylated N-terminus, sequence Ac-Ser-Asp-Ala-Ala-Val-Asp-Thr-Ser-Ser-Glu-Ile-Thr-Thr-Lys-Asp-Leu-Lys-Glu-Lys-Lys-Glu-Val-Val-Glu-Glu-Ala-Glu-Asn (Ac-SDAAVDTSSEITTKDLKEKKEVVEEAEN), molecular formula C₁₂₉H₂₁₅N₃₃O₅₅, molecular weight 3108.28 g/mol and CAS number 62304-98-7. It is the N-terminal 28-residue fragment of prothymosin alpha, the acidic nuclear protein from which it is released by proteolysis, and it was first isolated from bovine thymus, specifically from calf thymosin fraction 5, and sequenced by Goldstein and colleagues (Proc Natl Acad Sci USA, 1977). The N-terminal acetylation is the molecule's defining chemical feature: it blocks aminopeptidase degradation and is considered necessary for full activity. The sequence contains no cysteine and no methionine, so TA1 carries no disulfides and is spared the methionine-oxidation liability that dominates handling guidance for many other research peptides; what it does carry is a C-terminal asparagine, which makes deamidation the principal degradation route to design against.

This page covers the 5mg presentation, the lower-mass research format of the compound supplied in the 10mg vial. The molecule is identical in both sizes: same sequence, same molecular weight, same receptor pharmacology, with the full chemistry and literature documented on the main Thymosin Alpha-1 page. What differs is vial content. The 5mg vial holds half the lyophilised mass in the same single-vial glass format, so a given fill volume yields half the concentration of the 10mg vial, and each size is its own batch with its own certificate of analysis. The 5mg format suits pilot and screening designs with a smaller total peptide mass, and its shorter in-use window naturally limits the cumulative deamidation history any one reconstituted stock accumulates.

The regulatory history is unusual for a peptide in this catalogue and worth stating precisely. Under the brand name Zadaxin, developed by SciClone Pharmaceuticals, thymosin alpha-1 (thymalfasin) is licensed as a prescription medicine in more than 35 countries, principally in Asia and the Middle East, for immunomodulatory indications most notably including chronic hepatitis B. The evidence base includes randomised controlled trials such as Chien and colleagues' 98-patient trial (Hepatology, 1998), and the history is reviewed by Camerini and Garaci (Expert Opin Biol Ther, 2015). It has never been licensed in the United Kingdom, the European Union or the United States. That asymmetry matters for researchers: a compound with a genuine pharmaceutical dossier in some jurisdictions remains an unlicensed substance in others, and no thymosin alpha-1 product is an approved medicine in the UK.

Mechanistically, the most cited modern work centres on toll-like receptor signalling rather than a classical single receptor. Romani and colleagues reported in Blood (2004) that thymosin alpha 1 activates myeloid dendritic cells for Th1-type responses through a TLR9-dependent, MyD88-mediated signalling pathway. Around that anchor sit the older T-cell literature, maturation, differentiation and function of thymocytes and peripheral T cells, alongside reports of natural killer cell activity and broad cytokine regulation, reviewed by Garaci (Ann N Y Acad Sci, 2007). The most active current direction is oncology, including a 2025 retrospective analysis of TA1 added to PD-1/PD-L1 inhibitor plus chemotherapy in platinum-resistant recurrent ovarian cancer (Wang et al., Cancer Manag Res, 2025). The honest position follows: the licensed indications are prescription medicine uses in specific jurisdictions, nothing on this page describes or endorses any human use, and the material supplied here is for in-vitro laboratory research only. Much of the older immunology literature is small and heterogeneous, and the recent checkpoint-inhibitor combination data are largely retrospective. Thymosin alpha-1 is supplied as lyophilised powder, batch UKPL-9508, at 99.48% purity by HPLC with the supplier certificate of analysis published on the product page, with independent third-party verification pending.