BOARD 00 // REVIEWS / THYMOSIN ALPHA-1 / Ac-SDAAVDTSSEIT...
Thymosin alpha-1 has been studied in hepatitis, sepsis, oncology and severe COVID-19 — here is what the literature actually shows.
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
<a id="synonyms"></a>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 anchor the regulatory approval. The Wu 2013 ETASS sepsis RCT anchors the critical-care record [6]. The Liu 2020 Wuhan COVID cohort [8] and the Matteucci 2023 PASC study [11] anchor the pandemic-era data. The Liang 2020 NSCLC paper in Biomedicine & Pharmacotherapy anchors oncology adjuvant research [15]. For full editorial coverage, open the Thymosin alpha-1 benefits round-up, the Thymosin alpha-1 dosage protocols, and the frequently asked questions.
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].