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 Phase III primary result.
Safety
FDA states compounded Ta1 may pose immunogenicity/impurity risk and that available safety information is inadequate for proposed compounded products.
i
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.
What the evidence actually supports
✓The large null trial should be highly visible whenever thymosin alpha-1 is discussed for sepsis/immunomodulation.
✓This should outrank older small positive sepsis studies on the page.
✓Ideal example for the site's 'why evidence changed' module.
✓Historical disease-specific evidence, not a general immune-boosting claim.
What is not established / key limitations
×No mortality benefit in the Phase III trial.
×No overall mortality benefit; HR 0.99, P=0.93.
×High-quality/multicenter subsets did not show a significant mortality benefit, consistent with the large TESTS trial.
×The evidence predates modern nucleos(t)ide-analogue treatment standards.
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.
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.
Dosing evidence statusVerified dosing evidence added. Published human clinical-use regimen. See dosing_evidence records for route, regimen, population, duration and source.
Evidence rule: WhichPeps keeps human, animal, laboratory, regulatory and product/formulation evidence distinct. Common names help people find the page; they do not change the underlying scientific identity.
