Human RCT
Mensch
Chien RN. et al. 2001
Improvement of seroconversion rates in chronic hepatitis B observed in some randomised trials
What does NOT follow: Data are heterogeneous; later meta-analyses showed varying effect sizes.
Peptide entry · Healing
Thymosin Alpha-1
TA1 · Tα1 · Zadaxin
Highest evidence
Human RCT
Studies recorded
2· 2 in humans
Legal status · US
UnapprovedScientific context only. Not medical advice, not a recommendation to use.
At a glance
Synthetic 28-amino-acid peptide identical to a naturally occurring thymus peptide. Approved as Zadaxin in more than 30 countries (not US/EU) for hepatitis B treatment and as an immunomodulator.
Researched for
Chronic hepatitis BSepsis (adjunctive)Immune modulation in immunosuppressionCOVID-19 (early-pandemic studies)
Official status
US: Unapproved
No FDA approval. In 2020 the FDA removed thymosin alpha-1 from the 503A compounding list — pharmacies may no longer routinely compound it.
01
Mechanism of action
Thymosin Alpha-1 is an N-terminally acetylated peptide originally isolated from the thymus. It modulates T-lymphocyte maturation and function and acts on dendritic cells via Toll-like receptors (TLR9 / TLR2). In preclinical and some clinical studies, increased interferon-gamma responses and altered T-cell subpopulations have been reported.
02
Evidence at a glance
Reading note. The distribution shows on which evidence tier each observation sits. Strong colours mark stronger evidence — weaker tiers are deliberately visible, not hidden.
03
What the studies show
Human RCT
Mensch
Wu J. et al. 2013
Reduction in 28-day mortality in severe sepsis reported in a Chinese multicentre trial (ETASS)
What does NOT follow: Single trial, no consistent replication in Western sepsis cohorts.
Human trial
Mensch
Modulation of T-cell subpopulations in immunocompromised patients documented in preclinical and small clinical studies
What does NOT follow: Mechanistic findings; clinical endpoint relevance not consistently demonstrated.
04
Where studies disagree
Open question
Is thymosin alpha-1 efficacy in sepsis reproducible in Western cohorts?
POSITION A
ETASS (China) reported significant 28-day mortality reduction.
POSITION B
Later smaller trials outside China could not consistently replicate the effect.
CURRENT STATE · A larger multicentre replication trial (TESCEX) was planned in 2020; results pending.
05
Pharmacokinetics
Theoretical concentration curve at a half-life of 2 h. Pure pharmacokinetic model — not a dosing recommendation.
Open in PK tool →Start time: t₀ = 0h
Repeat interval: off (single dose)
06
Routes of administration in the literature
Which routes of administration the available studies describe — neutral reporting, not a usage guide.
Subcutaneous
In the hepatitis B trials administered twice weekly subcutaneously; once daily in ETASS.
07
Known adverse events from studies
Factual reporting of what studies observed. Not a safety statement for individual use.
Human RCT
Local injection-site reactions
From aggregated trials; in clinical datasets mostly mild and transient.
gelegentlich
07b
Interactions & combinations
Documented interactions and contraindications from studies, prescribing information and guidelines. Where no data exists, this is stated.
Reporting of risks, NOT a combination guide. The absence of an entry does not mean „safe to combine“ but „not sufficiently studied“.
No documented interactions recorded
We have not yet found robustly documented interactions for this peptide. This does NOT mean none exist — the data is limited.
09
Regulatory voices
Direct statements from official assessment documents — paraphrased with date and source link.
FDAU.S. Food and Drug Administration
2020-08-01FDA decision on the 503A bulk drug list, 2020.
The agency has determined that this substance does not meet the criteria for inclusion.
11
Legal status by country
12
Reconstitution calculator
Pure mg/mL maths — works like a calculator. Not a usage recommendation.
Peptides ship as a dry powder. Once dissolved in a liquid (reconstitution), this calculator answers a single question: how much substance is in one millilitre of solution afterwards?
- 1Enter the vial's substance amount (printed on the label).
- 2Enter how much solvent you add.
- 3Result = concentration in mg per mL.
Printed on the label
/
Liquid you add
=
2.50
mg / mL
5 mg in 2 mL gives 2.50 mg/mL — each millilitre contains 2.50 mg of substance.
14
Study register
Human RCTRandomised controlled trial
Chien RN. et al. · 2001
Thymosin alpha-1 in the treatment of chronic hepatitis B
Human RCTRandomised controlled trialn = 361
Wu J. et al. · 2013
Effect of thymosin alpha-1 on the 28-day mortality of severe sepsis (ETASS)
Concrete results
28-day mortality (absolute)
26.0% vs 35.0%
vs Kontroll-Arm · 28 Tage
15
Sources & method
Reviewed by
editor-placeholder
Last reviewed
2026-05-22
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