# Thymosin alpha-1: A Reviewed Digest of the Clinical Literature > Thymosin alpha-1, a 28-amino-acid immunomodulatory peptide, has been studied across hepatitis, sepsis, oncology, and severe COVID-19. A reviewed, cited digest of the literature. A reviewed digest of approved-indication trials, published meta-analyses, and receptor-level mechanism findings — chalked out, cited, and connected. ## What the Thymosin alpha-1 literature has demonstrated Thymosin alpha-1 is a 28-amino-acid N-terminally acetylated peptide originally isolated from calf thymus, with its sequence determined and published in 1977 [1]. The synthetic form, thymalfasin, is approved in 30+ countries primarily for chronic hepatitis B and C; the Dominari 2020 comprehensive review in World Journal of Virology is the most-cited synthesis of the corpus [2]. The molecule is unusually well-mapped: a defined sequence (Ac-SDAAVDTSSEITTKDLKEKKEVVEEAEN-OH), a molecular weight of 3,108 Da, and a receptor-level mechanism running through Toll-like receptor 9 and Toll-like receptor 2 on dendritic cells [4][5]. The headline findings repeat across indications. In chronic hepatitis B, the Yang 2008 Antiviral Research meta-analysis pooled randomized trials and concluded the peptide raised the odds of sustained virological response over interferon monotherapy [12]. In severe sepsis, the multicenter ETASS randomized double-blind trial (Wu 2013, Critical Care) reported a numerical reduction in 28-day all-cause mortality on 1.6 mg subcutaneously twice daily then daily [6], and the Li 2015 International Journal of Infectious Diseases meta-analysis pooled trials to a significant overall mortality benefit [7]. In severe COVID-19, the Liu 2020 Wuhan cohort (n=76) reported a fall in 28-day mortality from 30.0% to 11.1% (p=0.044) with adjunctive use, alongside restoration of lymphocyte counts and reversion of exhausted T cells [8]. ## The Thymosin alpha-1 Peptide The Thymosin alpha-1 peptide is 28 amino acids long, N-terminally acetylated, and derived from prothymosin alpha [1]. Sequence: `Ac-SDAAVDTSSEITTKDLKEKKEVVEEAEN-OH`. Molecular weight: 3,108.3 Da. Class: peptide immunomodulator. Mechanistically, the Thymosin alpha-1 peptide engages TLR-9 on plasmacytoid dendritic cells and TLR-2/MyD88 on conventional dendritic cells [4][5]. Downstream, dendritic cells mature, T-cell counts and CD4/CD8 ratio recover, IFN-γ and IL-2 production increases, and the cytokine balance shifts toward a Th1 antiviral phenotype. The Romani 2006 study in Blood demonstrated that Tα1 also activates the indoleamine 2,3-dioxygenase (IDO) tryptophan-catabolism axis in dendritic cells, establishing a regulatory environment that balances inflammation and tolerance — the molecule is immunomodulatory rather than purely immunostimulatory [4]. The Bozza 2007 murine cytomegalovirus model in International Immunology demonstrated TLR-9/MyD88/IRF7-dependent type-I interferon induction by Tα1 in vivo [5]. ## TA1 Peptide: Abbreviation and Synonyms TA1 peptide, Tα1, thymalfasin, and Zadaxin all refer to the same 28-amino-acid molecule. The naming history matters because it splits the literature across search indexes. **Thymosin alpha-1** is the discovery name from the 1977 Goldstein PNAS isolation [1]. **TA1 peptide** and **Tα1** are the abbreviations most common in immunology papers from the 2000s onward. **Thymalfasin** is the International Nonproprietary Name (INN) assigned to the synthetic form used in clinical trials and approved-product labelling [20]. **Zadaxin** is the SciClone Pharmaceuticals brand of thymalfasin approved in 30+ countries. For literature search, all four terms point at the same compound and the same clinical-trial corpus. Where this digest cites a trial, the trial used the synthetic peptide identical in sequence to the molecule first isolated from calf thymus fraction 5. ## Trial-by-Trial Review of Thymosin Alpha-1 The 2020 Dominari et al. comprehensive review in World Journal of Virology is the most-cited synthesis of the Thymosin alpha-1 literature [2]. This site's review framing follows the same trial-set spine: hepatitis B and C, severe sepsis, severe and post-acute COVID-19, oncology adjuvant therapy, vaccine adjuvant use, and post-transplant immune reconstitution. The [hepatitis B and C trials](/research#hepatitis) anchor the regulatory approval. The [Wu 2013 ETASS sepsis RCT](/research) anchors the critical-care record [6]. The [Liu 2020 Wuhan COVID cohort](/research) [8] and the [Matteucci 2023 PASC study](/research) [11] anchor the pandemic-era data. The Liang 2020 NSCLC paper in Biomedicine & Pharmacotherapy anchors [oncology adjuvant research](/research#oncology) [15]. For full editorial coverage, open the [Thymosin alpha-1 benefits](/benefits) round-up, the [Thymosin alpha-1 dosage](/dosage) protocols, and the [frequently asked questions](/faq). ## What is Thymosin alpha-1? A naturally occurring 28-amino-acid acetylated peptide first isolated from calf thymus fraction 5; the sequence was determined and published by Goldstein and colleagues in 1977 [1]. The synthetic form, thymalfasin, is the basis for the branded product approved in 30+ countries primarily for chronic hepatitis B and C [20]. The molecule sits within the larger thymosin protein family but is biologically distinct from Thymosin beta-4 and its fragment TB-500 (different protein, different mechanism). ## What does Thymosin alpha-1 do? Modulates innate and adaptive immunity by engaging TLR-9 and TLR-2 on dendritic cells, promoting T-cell maturation, raising IFN-γ and IL-2 output, and shifting the cytokine response toward a Th1 antiviral profile [4][5]. NK cell activity is recruited in parallel. The receptor-level mechanism was anchored by the Romani 2006 Blood paper on dendritic-cell tryptophan catabolism and the Bozza 2007 TLR-9/MyD88/IRF7 in vivo demonstration [4][5]. ## Conditions Studied in the Literature Across the published corpus, Thymosin alpha-1 has been studied in chronic hepatitis B and C (approved indications in 30+ countries; multiple RCTs and meta-analyses) [12][13][14], severe sepsis (ETASS RCT and subsequent meta-analyses) [6][7], severe COVID-19 (Wuhan and Italian cohorts plus 2023 meta-analyses) [8][9][22][23], non-small-cell lung cancer adjuvant therapy [15][16], influenza-vaccine adjuvancy in immunocompromised populations [18], and immune reconstitution after haploidentical hematopoietic transplantation [19]. It is also currently under FDA review for inclusion on the Section 503A compounding-bulks list [21]. --- Chalked up, erased, and chalked back again — a classroom-style review of the published Thymosin alpha-1 literature, not a clinical recommendation.