Independent · non-commercial · publishes on a quarterly cycle|Current cycle 2026 Q3
Compound Evidence InstituteEvidence synthesis · established 2023Graded assessments of compounds, trials, methods and supply
Document set current to 30 July 2026
Compound monograph · Immune modulators

Thymosin alpha-1 — compound monograph

28-residue N-acetylated thymic polypeptide. Approved. The Institute assesses 2 outcomes for this compound and grades the strongest at moderate certainty.

Document identifier
CEI-MN-040
Series
Compound monograph
Version
4.2
Published
23 Jan 2026
Last reviewed
23 Jan 2026
Next review
23 Jan 2028
Identifier
10.71829/cei.mono.40
Certainty
Moderate
Cycle
2026 Q1

§1Identification and status

§1.1Nomenclature

Preferred name
Thymosin alpha-1
Compound class
28-residue N-acetylated thymic polypeptide
Assessment series
Immune modulators
Synonyms and codes
Tα1 · thymalfasin · Zadaxin (trade) · thymosin α1
Route as evaluated
Subcutaneous

§1.2Chemistry

Chemical identifiers are reproduced where they are public. Where a structure has not been published the monograph records not disclosed rather than constructing one.[1]

CAS registry number
62304-98-7
Molecular formula
C129H215N33O55
Average mass
3108.29
Monoisotopic mass
3106.51
ATC classification
L03AX02

§1.3Sequence and structural notes

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-OH

A 28-residue N-acetylated peptide corresponding to the N-terminal region of prothymosin alpha. It is approved as thymalfasin in more than thirty countries, principally as an adjunct in chronic hepatitis B and C and as an immune adjuvant, which makes it one of only a handful of compounds in the research-peptide category with genuine marketing authorisations.

§1.4Assessment status

The Institute assesses Thymosin alpha-1 across 2 indications and grades the strongest of them at moderate certainty. Holds a marketing authorisation for at least one indication in at least one jurisdiction.

Distribution of certainty ratingsShare of assessed outcomes at each certainty level.1assessed outcomes
HighModerateLowVery low
Figure 1. Distribution of certainty ratings across the 2 outcomes the Institute assesses for Thymosin alpha-1. A rating attaches to a specific population, comparator and outcome and does not transfer between them.

Table 1. Assessed outcomes for Thymosin alpha-1, ordered by certainty. Each row links to the per-indication evidence extract.

IndicationEffect as recordedCertaintyTrials
Immune modulation and adjunctive immunotherapyMeta-analyses of hepatitis B trials report higher sustained virological response with thymosin alpha-1 as monotherapy or adjunct; a large Chinese…Moderate4
Cognitive performance and neuroprotectionNo evidence identifiedNot rated0
Effects are reproduced as the contributing trials reported them. Where a confidence interval is held it appears on the per-indication extract rather than in this summary table.

References cited on this page

References are numbered in order of first citation in this document. Each superscript in the text links to its entry below.

  1. International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use. ICH Q6B Specifications: Test Procedures and Acceptance Criteria for Biotechnological/Biological Products. ICH Harmonised Tripartite Guideline 1999;Step 4 version. identifier not held by the Institute

Identifiers are reproduced only where the Institute holds them. Where a digital object identifier or PubMed identifier is not shown, the Institute has recorded the journal and year and has not constructed an identifier.

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