Thymosin Alpha-1
Evidence: B/C — Meaningful Human EvidenceImmune / Inflammation
Key facts
- Research areaImmune / Inflammation
- Research statusinvestigational
- Study records129 human
- Last updated2026-07-30
Evidence Snapshot
What this grade covers
A for identity and FDA review history; B/C for mixed indication-specific human evidence; D/E for U.S. approval, broad immune restoration, sepsis mortality benefit, cancer treatment, chronic infection treatment, or consumer dosing.
Regulatory Context
No FDA-approved U.S. thymalfasin medicine was identified. Country-specific approval claims, including brand-name claims, require direct verification from the relevant regulator.
In Plain English
A quick, research-focused overview. It does not replace, and cannot outrank, the detailed evidence below.
What is it?
Thymosin alpha 1, or thymalfasin, is a defined immunomodulatory peptide studied in viral hepatitis, sepsis, pancreatitis, cancer, and other settings. Results are indication-specific and mixed.
Why are researchers interested in it?
Clinical trials have evaluated whether thymalfasin alters immune function or clinical outcomes in infectious, inflammatory, and oncology settings.
What is it being studied for?
- Chronic hepatitis B (thymalfasin)Human Studies & Clinical Data
- SepsisHuman Studies & Clinical Data
- Immune-modulation research in oncology and severe infection (adjunct combination studies)Human Studies & Clinical Data
What does the evidence look like?
Evidence grade B/C. Human, preclinical, regulatory, review, and anecdotal evidence must remain separated.
Biggest things to know
Positive small studies coexist with larger or more rigorous trials that did not confirm mortality or disease-response benefits. It must remain distinct from thymic extracts and other thymosins.
What don't we know yet?
In sepsis, an earlier trial (ETASS) suggested a possible mortality benefit, but the larger, more recent TESTS trial found no clear evidence that thymosin alpha-1 reduces 28-day all-cause mortality — a case where a bigger, later study did not confirm an earlier positive signal. Evidence in chronic hepatitis B is mixed across trials, and efficacy appears indication-specific rather than a general immune-boosting effect. Thymalfasin's use or authorization in some countries does not establish FDA approval for use in the United States, and FDA has identified immunogenicity and peptide-impurity concerns relevant to compounded thymosin alpha-1 products.
Research status
Reviewed August 25, 2026
Research Takeaway
Thymosin alpha-1 is an N-terminally acetylated 28-amino-acid peptide; thymalfasin is the chemically produced clinical form with the same amino-acid sequence, while thymosin alpha-1 free base and thymosin alpha-1 acetate are distinct bulk-substance forms for regulatory purposes.
Evidence boundary: Thymosin alpha-1 must not be merged with Thymalin, thymosin beta-4/TB-500, thymulin, or other thymic preparations.
See all 6 evidence claims →Quick Summary
Thymosin alpha 1, or thymalfasin, is a defined immunomodulatory peptide studied in viral hepatitis, sepsis, pancreatitis, cancer, and other settings. Results are indication-specific and mixed.
Mechanism & Research Overview
Thymosin alpha 1 is a defined 28-amino-acid peptide, also known as thymalfasin, studied as an immunomodulator. It is distinct from Thymalin, thymosin beta-4, thymulin, and Thymogen.
Mechanism pathway
Relationship-support labels describe the type and directness of the research available, not proof of safety or effectiveness. Indirectly supported, inferred and uncertain relationships are not equivalent to directly supported ones.
- CompoundThymosin Alpha-1
- Supported indirectly (Indirectly supported relationship)Biological targetTLR9 receptorReceptor
- Leads toPathwayImmune & Inflammatory Signaling
Relationship details
- Thymosin Alpha-1 → TLR9 receptor — Supported indirectlyThymosin Alpha-1's anti-viral and immunomodulatory effects in mice occur through TLR9/MyD88-dependent plasmacytoid dendritic-cell signaling, without demonstrated direct physical binding of Thymosin Alpha-1 to TLR9.
Evidence Claims
Individual scientific statements drawn from the sources cited below, each shown with the specific evidence boundary that statement does not establish.
Supported
Thymosin alpha-1 is an N-terminally acetylated 28-amino-acid peptide; thymalfasin is the chemically produced clinical form with the same amino-acid sequence, while thymosin alpha-1 free base and thymosin alpha-1 acetate are distinct bulk-substance forms for regulatory purposes.
Does not establish
Evidence boundary: Thymosin alpha-1 must not be merged with Thymalin, thymosin beta-4/TB-500, thymulin, or other thymic preparations.
Supported
Thymosin alpha-1/thymalfasin has been studied in multiple randomized human trials for chronic hepatitis B, with some trials reporting virologic or biochemical responses.
Does not establish
Evidence boundary: The existence of positive HBV trials does not establish efficacy for unrelated infections, cancer, vaccination, wellness, or anti-aging uses.
Sources: Thymosin alpha 1 in chronic hepatitis B: randomized clinical study; Thymosin alpha 1 treatment of chronic hepatitis B: a phase III randomized double-blind placebo-controlled study
Supported
In sepsis, the earlier ETASS randomized trial suggested benefit, but the larger, more recent TESTS multicenter double-blind randomized trial found no clear evidence that thymosin alpha-1 reduced 28-day all-cause mortality.
Does not establish
Evidence boundary: The larger contemporary negative trial materially limits broad claims based on the earlier positive sepsis study.
Sources: The efficacy of thymosin alpha 1 for severe sepsis: ETASS randomized trial; The efficacy and safety of thymosin alpha 1 for sepsis: TESTS randomized clinical trial
Supported
Clinical trials provide substantial human exposure experience, but U.S. FDA has also identified immunogenicity and peptide-impurity/characterization concerns relevant to compounded thymosin-alpha-1 products.
Does not establish
Evidence boundary: Safety of a characterized clinical product cannot automatically be transferred to every compounded or research-market formulation.
Sources: FDA PCAC Final Summary Minutes, December 2024; FDA summary of identified safety risks for compounded cathelicidin LL-37
Supported
At the December 4, 2024 FDA Pharmacy Compounding Advisory Committee meeting, members voted 4 yes, 17 no, and 0 abstentions on whether thymosin alpha-1 free base and, separately, thymosin alpha-1 acetate should be placed on the 503A Bulks List; FDA's materials proposed that they not be included.
Does not establish
Evidence boundary: An advisory-committee vote is not itself a drug-approval decision and must not be described as FDA approval or universal prohibition.
Supported
Thymosin alpha-1 has a materially stronger human evidence base than most Batch 7 subjects, but efficacy is indication-specific and mixed; foreign clinical use or authorization of thymalfasin does not create U.S. FDA approval for generalized use.
Does not establish
Evidence boundary: Grade B/C reflects real randomized human evidence together with mixed outcomes and regulatory/jurisdictional limitations.
Sources: The efficacy and safety of thymosin alpha 1 for sepsis: TESTS randomized clinical trial; FDA PCAC Final Summary Minutes, December 2024
Safety & Evidence Limitations
Considerations reported in the sources cited on this page — not a complete list of every possible risk, and not medical advice.
Safety Consideration
Evidence and outcomes differ substantially by disease, combination therapy, and trial quality.Safety Consideration
The 2025 TESTS sepsis trial did not show clear 28-day mortality benefit.Safety Consideration
Country-specific product approvals and quality standards cannot be assumed from a catalog name.Safety Consideration
Important uncertainties include immunogenicity and anti-drug antibodies; aggregation and peptide-related impurities; free-base versus acetate identity; injection-site reactions; fever, fatigue, headache, nausea, or flu-like symptoms; immune activation or suppression in autoimmune, transplant, cancer, or infection settings; interactions with immunosuppressants, immune checkpoint inhibitors, chemotherapy, vaccines, and antivirals; uncertain pregnancy, pediatric, hepatic, renal, and long-term repeated-dose safety; sterility and endotoxin risks for compounded injectable products; and absence of a comprehensive U.S. approved-product pharmacovigilance program. The negative TESTS efficacy result should not be mistaken for proof of long-term safety in other populations.
Research Areas Being Studied
Research areas discussed on this page reflect the Immune / Inflammation category and the sources cited below.
Findings Reported in Studies
Educational summary only — reported in cited studies, not a claim of proven benefit.
Show findings from 9 human studies
- The efficacy and safety of thymosin alpha 1 for sepsis: TESTS randomized clinical trial (2025):
- Thymosin alpha 1 in hospitalized COVID-19: randomized pilot study (2022):
- The efficacy of thymosin alpha 1 for severe sepsis: ETASS randomized trial (2013):
- Thymosin alpha 1 and cellular immunity in severe acute pancreatitis: double-blind randomized study (2011):
- Thymosin alpha 1 in advanced melanoma: randomized clinical study (2010):
- Randomized placebo-controlled study of thymosin alpha 1 plus interferon for chronic hepatitis C (2006):
- Thymosin alpha 1 treatment of chronic hepatitis B: a phase III randomized double-blind placebo-controlled study (1999):
- Thymosin alpha 1 in chronic hepatitis B: randomized clinical study (1998):
- Thymosin Alpha-1 and Influenza Vaccine Response ():
Study Tables by Evidence Type
12 study records
Human Studies & Clinical Data(9)
The efficacy and safety of thymosin alpha 1 for sepsis: TESTS randomized clinical trial
2025PMID 39814420
- Population / Model
- Adults with sepsis in a large randomized trial
- Dose / Duration / Finding
The TESTS trial found no clear evidence that thymosin alpha 1 decreased 28-day all-cause mortality.
Safety note
The result weighs against presenting sepsis mortality benefit as established.
Thymosin alpha 1 in hospitalized COVID-19: randomized pilot study
2022PMID 36056913
- Population / Model
- Hospitalized adults with COVID-19 in a pilot randomized study
- Dose / Duration / Finding
The pilot evaluated immune and clinical outcomes but was not definitive for mortality or routine use.
Safety note
Small sample and changing standard-of-care limit generalization.
The efficacy of thymosin alpha 1 for severe sepsis: ETASS randomized trial
2013PMID 23327199
- Population / Model
- Adults with severe sepsis in a multicenter randomized trial
- Dose / Duration / Finding
ETASS reported immune-marker and mortality findings that motivated further study, but later confirmatory evidence was needed.
Safety note
Critical-care co-interventions and trial design limit generalization.
Thymosin alpha 1 and cellular immunity in severe acute pancreatitis: double-blind randomized study
2011PMID 20549321 · DOI 10.1007/s10753-010-9224-1
- Population / Model
- 24 patients with severe acute pancreatitis
- Dose / Duration / Finding
The pilot study reported improved immune markers and lower infection-related outcomes in the thymosin group.
- Study/Trial Dosing:
- 3.2 mg twice daily for 7 days in the trial.
- Duration:
- 7 days treatment with 28-day follow-up.
Safety note
Very small trial; clinical findings require confirmation.
Thymosin alpha 1 in advanced melanoma: randomized clinical study
2010PMID 20194853
- Population / Model
- Patients with advanced melanoma receiving chemotherapy with or without thymosin alpha 1
- Dose / Duration / Finding
The trial explored immune and clinical outcomes in combination therapy; it does not establish thymosin alpha 1 as an independent anticancer treatment.
Safety note
Combination-therapy attribution and disease heterogeneity limit interpretation.
Randomized placebo-controlled study of thymosin alpha 1 plus interferon for chronic hepatitis C
2006PMID 16640105
- Population / Model
- Adults with chronic hepatitis C receiving interferon-based therapy
- Dose / Duration / Finding
Adding thymosin alpha 1 did not establish a broad, stand-alone treatment effect under the studied combination regimen.
Safety note
Combination-therapy findings cannot be attributed solely to thymosin alpha 1.
Thymosin alpha 1 treatment of chronic hepatitis B: a phase III randomized double-blind placebo-controlled study
1999PMID 10607256 · DOI 10.1046/j.1365-2893.1999.00181.x
- Population / Model
- 97 patients with HBeAg-positive chronic hepatitis B
- Dose / Duration / Finding
The phase III trial did not confirm the efficacy signals reported in some earlier studies; response differences were not statistically conclusive.
- Study/Trial Dosing:
- 1.6 mg twice weekly in the trial.
- Duration:
- 6 months treatment plus 6 months follow-up.
Safety note
Twice-weekly treatment was studied for six months with follow-up, but efficacy remained uncertain.
Thymosin alpha 1 in chronic hepatitis B: randomized clinical study
1998PMID 9581695
- Population / Model
- Adults with chronic hepatitis B
- Dose / Duration / Finding
The study evaluated delayed virologic and biochemical responses after a thymosin alpha 1 course.
Safety note
Older, modest-sized study; results require context alongside later negative or inconclusive trials.
Thymosin Alpha-1 and Influenza Vaccine Response
PMID 2642497
- Population / Model
- Dose / Duration / Finding
Older small studies evaluated Thymosin Alpha-1 as an adjunct to influenza vaccination in selected immune-impaired populations. The evidence is old, heterogeneous, and insufficient to establish routine vaccine enhancement, prevention of influenza, or a general immune-boosting indication.
Show full finding
Animal / Cell / Preclinical Data
No Animal / Cell / Preclinical Data Listed Yet
This section will be updated as sources are added.
Regulatory Documents & Official Trial Registries(3)
FDA summary of identified safety risks for compounded cathelicidin LL-37
2026- Population / Model
- Dose / Duration / Finding
FDA states that compounded cathelicidin LL-37 may pose immunogenicity and peptide-impurity/API-characterization risks and that safety information is insufficient for proposed routes.
Safety note
FDA also cites nonclinical reproductive and tissue-specific protumorigenic concerns; this is compounding-risk context, not a finding that every LL-37 preparation causes those outcomes.
FDA PCAC Briefing Document for Thymosin Alpha-1 Free Base and Acetate
2024- Population / Model
- Dose / Duration / Finding
FDA's 2024 scientific review evaluated Thymosin Alpha-1 free base and acetate as distinct bulk drug substances across numerous infectious, immune, oncology, vaccine-response, and fatigue indications and concluded the evidence and safety characterization did not support adding either form to the 503A Bulks List, citing immunogenicity, aggregation/peptide-related impurities, incomplete active-ingredient characterization, and insufficient clinical safety information.
Show full finding
FDA PCAC Final Summary Minutes, December 2024
2024- Population / Model
- Dose / Duration / Finding
At the December 2024 Pharmacy Compounding Advisory Committee meeting, Thymosin Alpha-1 free base and acetate each received 4 votes for inclusion on the 503A Bulks List and 17 votes against, with 0 abstentions. The votes were advisory and nonbinding, not drug-approval decisions.
Show full finding
Anecdotal Reported Patterns — Not Medical Advice
Anecdotal Reported Patterns — Not Medical Advice
Reported dosing patterns are included for educational context only. They are self-reported, unverified, not medical advice, and not instructions for human use. Community-submitted patterns are not yet available in this Phase 1 prototype; this section is a placeholder reserved for moderated, aggregated community data.
Lab Markers to Discuss With a Clinician
Educational topics only — not self-monitoring instructions.
FAQ
Disclaimer
Educational information only. This page summarizes published and official research and does not provide medical advice, a recommendation, or instructions for human use.
Educational use only. This content is provided for informational and research-summary purposes only. It is not medical advice, not a treatment recommendation, not a dosing guide, and not a substitute for care from a licensed medical professional. Nothing here is intended to diagnose, treat, cure, prevent, or mitigate disease. Reported dosing patterns, when shown elsewhere on the site, must be labeled either as Study / Trial Dosing or Anecdotal Reported Patterns — Not Medical Advice. Community reports are self-reported, unverified, and not scientific proof.
Community-reported experiences, once enabled, must be displayed only as moderated, anonymized, or aggregated data. They are anecdotal, self-reported, unverified, and should never be presented as proof of safety, efficacy, or expected results.
Content status: Published. Last updated 2026-07-30.
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