Thymosin alpha-1

28-amino-acid immunomodulatory peptide

Infectious diseaseimmunomodulation

Thymosin alpha-1

Entity typePeptide

Evidence reviewed2026-09-18

Canonical recordTHYMOSIN_A1

Page updated2026-09-20

Evidence profileSubstantial heterogeneous human evidence; large Phase III sepsis result is null

Human evidenceSubstantial

Regulatory statusSome non-U.S. approvals

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Quick answerPlain language EvidenceOutcomes and studies StudiesPrimary records TechnicalMechanism, route and identifiers

In plain English

30-second evidence answer

What does the evidence mean in simple terms?

Thymosin alpha-1 has a sizeable but mixed human literature across different diseases. Older studies suggested benefit in some settings, but a large Phase 3 sepsis trial found no 28-day mortality benefit. The evidence therefore depends heavily on the exact indication.

Still uncertain: A broad immune-boosting or sepsis-survival benefit across populations; subgroup signals do not overturn the main Phase 3 result.

New to terms such as “preclinical”, “randomized” or “investigational”? Use the plain-English glossary →

What does the evidence mean in simple terms? table
What is it?	28-amino-acid immunomodulatory peptide
Entity type	Peptide
Research focus	Infectious disease, immunomodulation, oncology adjunct research
Human evidence	Human evidence is indication-dependent. Older sepsis studies/meta-analyses suggested benefit, but the 1,106-patient 2025 TESTS Phase III trial found no 28-day mortality benefit. Other older HBV and small COVID studies report indication-specific signals.
Regulatory status	Thymalfasin/TA1 has been used/approved in some countries for selected indications, but no FDA approval; jurisdiction and product matter.
Main limitations	A broad immune-boosting or sepsis-survival benefit across populations; subgroup signals do not overturn the main Phase 3 result.
Safety	FDA states compounded Ta1 may pose immunogenicity/impurity risk and that available safety information is inadequate for proposed compounded products.
Evidence reviewed	2026-09-18

Human evidence is indication-dependent. Older sepsis studies/meta-analyses suggested benefit, but the 1,106-patient 2025 TESTS Phase III trial found no 28-day mortality benefit. Other older HBV and small COVID studies report indication-specific signals.

Outcome-level evidence

Evidence is not one score.

Each record below answers a narrower question about an outcome, population or context. Evidence status and the study finding are shown separately so strong evidence is not mistaken for a positive effect.

How to read this →

Mortality benefit in sepsis

Human evidence

Large Phase III human evidence — null

Context: Adults with sepsis

Finding: The largest modern trial was negative.

Counter-evidence / null result: No mortality benefit in the Phase III trial.

Verified 2026-09-18Primary source ↗Supporting source ↗

28-day mortality in sepsis

Human evidence

Large randomized double-blind Phase III evidence

Context: Adults with sepsis

Finding: The highest-quality large sepsis trial was negative.

Counter-evidence / null result: No overall mortality benefit

Uncertainty / evidence gap: HR 0.99, P=0.93.

Verified 2026-09-18Primary source ↗

Why older sepsis meta-analyses looked positive

Human evidence

Evidence-evolution / meta-analysis synthesis

Context: Adults with sepsis

Finding: Evidence quality materially changes the conclusion.

Counter-evidence / null result: High-quality/multicenter subsets did not show a significant mortality benefit, consistent with the large TESTS trial.

Verified 2026-09-18Primary source ↗Supporting source ↗

Chronic hepatitis B virological/biochemical response

Human evidence

Older meta-analysis of four randomized trials

Context: Mostly HBeAg-negative chronic hepatitis B

Finding: A delayed-response signal exists in older HBV studies.

Uncertainty / evidence gap: The evidence predates modern nucleos(t)ide-analogue treatment standards.

Verified 2026-09-18Primary source ↗

Mortality in moderate-to-severe COVID-19

Human evidence

Small randomized Phase III study

Context: Adults hospitalized with COVID-19

Finding: A positive signal was reported in this specific early-pandemic study.

Uncertainty / evidence gap: This does not establish benefit across current COVID care or other infections.

Verified 2026-09-18Primary source ↗

Evidence rule: an outcome-specific evidence label is not a recommendation, a safety rating or an overall score for the compound.

Evidence synthesis

✓The largest modern trial was negative.
✓The highest-quality large sepsis trial was negative.
✓Evidence quality materially changes the conclusion.
✓A delayed-response signal exists in older HBV studies.
✓A positive signal was reported in this specific early-pandemic study.

Important limitations

!Earlier heterogeneous studies/meta-analyses may overstate effect; indication-specific evidence differs.
!Potential subgroup differences are exploratory and do not overturn the primary result.
!Clinical heterogeneity, small-study effects and subgroup analyses.
!Only 199 total participants; small trials; older treatment landscape.
!Small sample, single-country/era-specific standard of care and disease-specific context.

Selected study & evidence records

Thymosin alpha-1 versus interferon alpha for chronic hepatitis B: meta-analysis

2008 · Meta-analysis of randomized controlled trials · n=199

At end of treatment, thymosin alpha-1 was not clearly superior; at 6-month post-treatment follow-up, pooled virological, biochemical and complete responses favored thymosin alpha-1.

Study detail → Primary source ↗

ETASS: thymosin alpha-1 for severe sepsis

2013 · Multicenter randomized controlled trial; single-blind · n=361

Mortality was 26.0% versus 35.0%; RR 0.74 (95% CI 0.54-1.02), with borderline/mixed significance depending on analysis; mHLA-DR improved.

Study detail → Primary source ↗

Thymosin alpha-1 as add-on treatment in moderate-to-severe COVID-19

2022 · Double-blind, multicenter, randomized, placebo-controlled trial · n=105

Mortality was reported as 11.1% in the thymosin arm versus 38.5% placebo.

Study detail → Primary source ↗

TESTS Phase III thymosin alpha-1 sepsis trial

2025 · Randomized multicenter controlled trial · n=1106

Mortality was 23.4% versus 24.1% (HR≈0.99; P=.93): no mortality benefit.

Study detail → Primary source ↗

Safety and unknowns

FDA states compounded Ta1 may pose immunogenicity/impurity risk and that available safety information is inadequate for proposed compounded products.

Human exposure is substantial relative to many research peptides, but safety and benefit remain indication-specific. It is not FDA-approved, and compounded use raises additional quality/regulatory considerations.

Technical details

Mechanism / biologyModulates innate/adaptive immune signalling including T-cell and dendritic-cell functions.

Route / formulation boundaryDo not generalize outcomes across hepatitis, sepsis, cancer, COVID-19 or wellness indications.

Identity / data-quality noteUse the canonical compound identity and studied formulation when interpreting evidence.

Study / label regimen evidenceVerified study/label regimen evidence is available. Published human clinical-use regimen. Open descriptive regimen evidence →

Identifiers & alternate namesTA1 · Thymalfasin · Thymosin alpha 1

Source depth & provenance

WhichPeps does not rely on a single headline study when the evidence base is broader. Primary research, registries, regulators and supporting records are kept distinct.

4structured study records

5outcome records

11linked source records

How to read these counts: they show evidence coverage, not evidence strength. One large, well-designed study can be more informative than several weak or indirect records.

Show supporting and discovery sources

Study pages above contain the records used for public evidence summaries. The links below include supporting, regulatory and literature-discovery sources; a registry or search result is not treated as proof of benefit.

PubMed / peer-reviewed source ↗ — Supports the evidence summary; read full paper before quoting exact endpoints.
FDA source ↗ — Regulatory status, approved indication, or safety/compounding context.
PubMed / peer-reviewed source ↗ — Discovery link for the continuously growing peer-reviewed literature.
ClinicalTrials.gov record/search ↗ — Discovery link for registered interventional/observational studies.
PubMed / peer-reviewed source ↗ — Supports contraindication, interaction, monitoring, pregnancy or formulation-safety context in the safety evidence layer.
FDA source ↗ — Supports contraindication, interaction, monitoring, pregnancy or formulation-safety context in the safety evidence layer.
PubMed / peer-reviewed source ↗ — TESTS sepsis trial
PubMed / peer-reviewed source ↗ — Sepsis evidence synthesis
PubMed / peer-reviewed source ↗ — ETASS: thymosin alpha-1 for severe sepsis
PubMed / peer-reviewed source ↗ — Thymosin alpha-1 versus interferon alpha for chronic hepatitis B: meta-analysis
PubMed / peer-reviewed source ↗ — Thymosin alpha-1 as add-on treatment in moderate-to-severe COVID-19

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