Thymosin alpha-1: research

An immune-signaling peptide with overseas approvals and mixed trial results.

Also called: Thymalfasin, TA1, Tα1, Thymosin α1, Zadaxin.

Immune peptides · Synthetic 28-amino-acid thymic immune modulator · Evidence: Approved drug.

Major sepsis and hepatitis C trials found no clear benefit. Hepatitis B findings remain uncertain, and reviews reuse some of the same trial data.

Studies

Early injection dose study (1983). open-label, n=28, Adults with advanced cancer; 14 received TA1 and 14 received thymosin fraction 5. Short-lived immune-test changes did not establish an anticancer benefit. (source)
Absorption and half-life (1999). pk-study, n=9, Healthy White adult volunteers. Formulation affects exposure; a short blood half-life does not set an effective dosing interval. (source)
Early hepatitis B pilot (1991). rct, n=12, Adults with active chronic hepatitis B. A tiny mixed-product pilot cannot isolate TA1 benefit. (source)
Hepatitis B versus interferon (1996). rct, n=33, Adults with anti-HBe-positive, HBV-DNA-positive hepatitis B. This small trial did not show a clear advantage over interferon. (source)
Hepatitis B: six or twelve months (1998). rct, n=98, Adults with chronic hepatitis B. A delayed viral response favored six months of dosing in this small trial. (source)
Hepatitis B placebo trial (1999). rct, n=97, Adults with HBeAg-positive, HBV-DNA-positive hepatitis B. The placebo-controlled phase 3 trial did not confirm efficacy. (source)
Hepatitis B untreated comparison (2000). rct, n=44, Adults with anti-HBe-positive, HBV-DNA-positive hepatitis B. TA1 did not clearly improve the response rate. (source)
Hepatitis B: two-week loading (2003). rct, n=16, Adults with chronic hepatitis B. This very small dose comparison cannot establish an optimal loading schedule. (source)
Hepatitis B: 0.8 versus 1.6 mg (2005). rct, n=316, Japanese adults with HBV DNA and raised ALT. The higher dose did not show a clear overall advantage. (source)
Hepatitis B: add-on to peginterferon (2012). rct, n=51, Adults with HBeAg-positive chronic hepatitis B. Adding TA1 for 12 weeks did not improve response. (source)
Entecavir plus TA1 in cirrhosis (2018). rct, n=690, Adults with compensated HBV-related cirrhosis after 26 weeks of entecavir. The large cirrhosis trial did not show a clear clinical-outcome benefit. (source)
Hepatitis B liver failure trial (2022). rct, n=120, Adults with HBV-related acute-on-chronic liver failure; 114 in reported comparison. One survival analysis favored TA1, but a competing-risk analysis did not. (source)
Cochrane hepatitis B review (2026). meta-analysis, n=1349, Ten randomized trials of adults with chronic hepatitis B. The reviewers remain unsure about benefit because most evidence is very uncertain. (source)
Hepatitis C: TA1 alone (1996). rct, n=19, Adults with chronic hepatitis C. TA1 alone did not show activity against chronic hepatitis C. (source)
Hepatitis C: add-on to interferon (1998). rct, n=109, Adults with biopsy-confirmed chronic hepatitis C. Short-term viral and liver-test changes did not establish a sustained viral benefit. (source)
Hepatitis C: triple therapy (2012). rct, n=552, Adults whose HCV had not responded to peginterferon plus ribavirin. TA1 did not improve the main hepatitis C response. (source)
Hepatitis C phase 3: no cirrhosis. rct, n=500, Adults with HCV that failed interferon-based treatment. These completed phase 3 records do not provide usable arm-level results. (source)
Hepatitis C phase 3: cirrhosis. rct, n=500, Adults with HCV that failed interferon-based treatment. These completed phase 3 records do not provide usable arm-level results. (source)
ETASS sepsis trial (2013). rct, n=361, Adults with severe sepsis in six Chinese hospitals. The main mortality comparison did not reach statistical significance. (source)
TESTS phase 3 sepsis trial (2025). rct, n=1106, Adults aged 18-85 with sepsis in 22 Chinese centers. The largest placebo-controlled sepsis trial found no survival benefit. (source)
Reset-alpha sepsis abstract (2024). rct, n=120, Adults with sepsis; 120 completers in ten Indian centers. A small conference abstract reported better organ scores but leaves key details unclear. (source)
Sepsis review after TESTS (2025). meta-analysis, n=1927, Eleven randomized sepsis trials; combination-drug trials excluded. The pooled benefit disappeared in the higher-quality trials. (source)
India COVID placebo trial (2022). rct, n=105, 65 adults with moderate COVID-19 and 40 with severe disease. A small trial favored TA1, but dose wording and reporting limit confidence. (source)
US hospitalized COVID pilot (2023). rct, n=49, Hospitalized adults with low oxygen and low lymphocyte counts. The pilot did not establish a faster clinical recovery. (source)
Dialysis COVID prevention: final results. rct, n=189, Adults on hemodialysis in the US. Few infections occurred, leaving prevention benefit uncertain. (source)
Large COVID cohort (2021). cohort, n=2282, Hospitalized adults with COVID-19 in five Chinese hospitals. TA1 exposure was associated with worse recovery in this cohort. (source)
Critical COVID matched cohort (2021). cohort, n=771, Adults with critical COVID-19 in 19 Chinese hospitals. The apparent survival advantage disappeared after matching. (source)
COVID review: no overall benefit (2023). meta-analysis, n=5352, Nine studies of hospitalized adults with COVID-19. This review did not support routine TA1 use in hospitalized adults. (source)
COVID review: conflicting result (2023). meta-analysis, Eight studies of adults with moderate-to-critical COVID-19. Different study selection produced a positive but highly inconsistent pooled result. (source)
Severe pancreatitis pilot (2011). rct, n=24, Adults with severe acute pancreatitis. A small pilot reported immune and infection improvements. (source)
TRACE pancreatitis trial (2022). rct, n=508, Adults with predicted severe acute necrotizing pancreatitis. The larger blinded trial did not prevent infected pancreatic necrosis. (source)
Melanoma: 1.6, 3.2 or 6.4 mg (2010). rct, n=488, Adults with metastatic melanoma. Response counts differed, but a survival benefit was not established. (source)
Liver cancer plus TACE (2009). rct, n=25, Adults with unresectable liver cancer. The pilot was too small to establish a survival or tumor-response benefit. (source)
Flu vaccination in older men (1989). rct, n=90, Men aged 65-99 receiving trivalent influenza vaccine; 85 evaluable. This trial studied antibody response rather than reliable prevention of flu illness. (source)
H1N1 vaccine dose pilot (2012). open-label, n=99, Adults on hemodialysis receiving an adjuvanted H1N1 vaccine. The short-term antibody signal did not establish lasting vaccine benefit. (source)
HIV immune recovery pilot (2003). rct, n=20, Adults on HIV therapy with low CD4 counts and suppressed virus. A blood-marker change did not establish meaningful immune recovery. (source)
HIV nonresponders pilot (2024). single-arm, n=20, Adults with suppressed HIV but poor CD4 recovery; 17 completed. The main end-of-study immune endpoints did not clearly improve. (source)
Immune deficiency and depression pilot (2025). single-arm, n=5, Adults with common variable immune deficiency and depression. Five uncontrolled cases cannot establish an antidepressant effect. (source)
Radiation and immune therapy pilot (2025). single-arm, n=37, Adults with heavily pretreated metastatic solid tumors. A complex uncontrolled regimen cannot isolate TA1 effects. (source)
GATES gastric cancer pilot (2026). single-arm, n=30, Adults aged 18-75 with stage III gastric or gastroesophageal junction cancer. The uncontrolled cancer regimen cannot establish the added benefit of TA1. (source)
Gastric cancer review (2026). meta-analysis, n=1704, Twenty Chinese randomized trials of TA1 plus chemotherapy. Small trials suggest short-term changes, while survival benefit remains unknown. (source)
Cochrane cancer review (2011). meta-analysis, n=2736, 26 trials of several thymus extracts and peptides, including TA1. The TA1 subset did not show a clear survival benefit. (source)
Severe immune reaction case (2026). case-report, n=1, Adult with nasopharyngeal cancer receiving sintilimab and chemotherapy. A serious reaction after combined immune therapies warrants caution. (source)
COVID booster immune-response trial. rct, n=75, Registry population; no final clinical results available in the inspected record. Registration shows research activity, not demonstrated benefit. (source)
PANDA II aortic surgery study. rct, n=600, Registry population; no final clinical results available in the inspected record. Registration shows research activity, not demonstrated benefit. (source)
Entecavir add-on review (2020). meta-analysis, n=1144, Seven Chinese trials of HBV-related cirrhosis. Short-term laboratory changes did not establish lasting clinical benefit. (source)
Earlier sepsis review (2016). meta-analysis, Nineteen randomized sepsis trials, many small. An early positive mortality estimate came from low-quality small studies. (source)
Lung cancer peptide review (2019). meta-analysis, n=1925, 27 trials of synthetic thymic peptides with chemotherapy for lung cancer. The pooled signal does not establish TA1-specific benefit. (source)
Radiation lung-injury pilot (2022). cohort, n=138, 69 adults with locally advanced lung cancer plus 69 matched historical controls. The matched comparison suggests a benefit that needs randomized confirmation. (source)

Thymosin alpha-1 dosage

Typical reported dose: 1.6 mg twice a week for 26 weeks

Hepatitis B: 26 weeks: 1.6 mg twice weekly; no dose escalation. twice weekly, under the skin. Studied in a trial. Studied in: Adults with chronic hepatitis B. (source)
Hepatitis B: 52 weeks: 1.6 mg twice weekly; no dose escalation. twice weekly, under the skin. Studied in a trial. Studied in: Adults with chronic hepatitis B. (source)
Hepatitis B: 0.8 mg: 0.8 mg SC six times weekly., then 0.8 mg SC twice weekly for 22 weeks. six times weekly for two weeks, then twice weekly, under the skin. Studied in a trial. Studied in: Japanese adults with chronic hepatitis B. (source)
Hepatitis B: 0.8 mg loading: 0.8 mg six times weekly., then 0.8 mg twice weekly for 22 weeks. six times weekly for two weeks, then twice weekly, under the skin. Studied in a trial. Studied in: Adults in the 16-person hepatitis B pilot. (source)
Hepatitis B: 1.6 mg: 1.6 mg SC six times weekly., then 1.6 mg SC twice weekly for 22 weeks. six times weekly for two weeks, then twice weekly, under the skin. Studied in a trial. Studied in: Japanese adults with chronic hepatitis B. (source)
Hepatitis B: 1.6 mg loading: 1.6 mg six times weekly., then 1.6 mg twice weekly for 22 weeks. six times weekly for two weeks, then twice weekly, under the skin. Studied in a trial. Studied in: Adults in the 16-person hepatitis B pilot. (source)

These are doses reported in labels, trials or user reports, not a personal plan. Check the source behind each one.

Work out syringe units with the dosing calculator

Thymosin alpha-1 side effects and risks

Reported side effects

Injection-site discomfort or redness: Foreign information reports <1% drug related events overall in over 2,000 people; no site specific rate., mild. Report persistent pain, swelling or redness; worsening local changes can signal infection. (source)
Rash, joint pain or hand swelling: Described as rare in foreign product information; exact counts were not supplied., moderate. Stop dosing and seek assessment if symptoms spread or persist. (source)
Liver-test flares during hepatitis B dosing: 22/316 in the Japanese trial, 11 at each dose; arm specific percentages not extracted., moderate. Needs liver tests and clinical review; jaundice, confusion or bleeding need urgent care. (source)
Serious immune reaction with checkpoint therapy: One 2026 case involved fever, rash and multiple organ injury after sintilimab plus TA1., serious. Urgent assessment for fever, rash, breathing trouble or jaundice during cancer immune therapy. (source)
Events during intensive-care treatment: TESTS: any event 66.4% versus 67.6% placebo; serious events 26.8% versus 29.3%., serious. These are all-cause events in critically ill patients, not TA1-attributed side-effect rates. (source)
Worse fatigue, sleep or swollen glands: Self reports include worsening after 100 mcg once; no incidence or causality can be calculated., moderate. Do not assume a worsening reaction means the product is working. Seek assessment. (source)

Stop and get help if

Trouble breathing, throat or face swelling, widespread hives or fainting after an injection: Stop dosing and get emergency care for a possible severe allergic reaction.
High fever, rapidly spreading rash, chest tightness or new breathing trouble during cancer immune therapy: Seek urgent hospital assessment; severe immune toxicity and infection can look alike.
Jaundice, confusion, vomiting blood or new severe abdominal swelling: Get urgent care for possible liver failure or bleeding.
Worsening injection-site redness, warmth, pus or fever: Get prompt assessment for injection-related infection.

Who should avoid it

pregnant: Human pregnancy safety is unknown. Foreign product information does not establish fetal safety.
breastfeeding: It is unknown whether TA1 enters human milk or affects a nursing infant.
tryingToConceive: Reproductive safety in humans is not established; this is a precaution, not evidence of infertility.
under18: Safety and effectiveness below 18 are not established in the inspected foreign product information.
other: Foreign product information contraindicates use after hypersensitivity to TA1 or its ingredients.
other: Foreign instructions contraindicate deliberate immune suppression unless a specialist judges benefits outweigh risks.
immunosuppressed: Low immune function from HIV or cancer differs from deliberate immune suppression. Trials used specialist care and do not establish routine self-use.
autoimmuneDisease: Effects in active autoimmune disease are uncertain. Major sepsis trials excluded acute autoimmune disease.
liverDisease: Hepatitis B dosing can cause liver-test flares. Cirrhosis or liver failure needs disease-specific monitoring.
kidneyDisease: A small dialysis trial does not establish a general kidney-dose adjustment or long-term safety rule.
activeCancer: TA1 has been studied with cancer drugs, but a severe immune reaction was reported with checkpoint therapy. Coordinate with oncology.
testedAthlete: TA1 is not named in the 2026 list. Obtain a compound-specific ruling; the named thymosin beta-4 ban concerns a different peptide.

Interactions

Other immune-suppressing drugs: Review the reason for immune suppression and the intended TA1 effect. Formal interaction studies are incomplete.
Transplant immune-suppressing medicines: TA1 may oppose transplant immune suppression. Foreign instructions flag deliberate immune suppression as a contraindication.
Immune checkpoint inhibitors: Severe multi-organ immune toxicity was reported with sintilimab plus TA1. Risk across this drug class is unknown.
Interferon products: Studied together, but adds the risks of interferon; thyroid-function changes occurred in an older combination study.
Vaccines: TA1 has been studied as a vaccine add-on. Sustained benefit is uncertain, and combining it without review can alter immune response.
Other thymic or immune peptides: Check for duplicate TA1 exposure. Combining immune peptides has no established safety or interaction map.

Product quality risks

FDA flags peptide impurities, uncertain characterization and immune-reaction risk for compounded TA1.
Unregulated injections can have the wrong amount, unknown ingredients, particles, microbes or endotoxin.
A purity percentage does not establish the amount per vial, sterility, endotoxin level or clinical safety.

How Thymosin alpha-1 works

It changes how immune cells respond to signals. Lab studies suggest it helps some T cells mature and changes how immune cells recognize threats. More immune activity does not always mean better health.

Toll-like receptor signaling: Cell studies link TA1 to TLR2/TLR9 signaling and changes in dendritic-cell activity.
T cells and natural killer cells: Can change maturation and immune signaling. Clinical benefit depends on the disease and remains uncertain.

Half-life: About 2 hours in foreign product information; less than 3 hours in a nine-person crossover study.

Gaps: This is a curated profile, not a complete global trial census. The human-study count is a documented lower bound. No convincing trial evidence located for wellness, allergy relief, ME/CFS, long COVID or longevity cycles. One COVID trial and the Reset-alpha abstract have ambiguous two-injection dose wording. No complete results were found for two older US phase 3 HCV registrations. Pregnancy, breastfeeding, reproductive and long-term healthy-user safety remain unknown. No validated oral, nasal or transdermal human dosing protocol was located. No TA1-specific independent survey of online vial purity, content, endotoxin and sterility was located. No established interactions with insulin, sulfonylureas or anticoagulants were found; lack of study does not prove compatibility. Community prevalence is qualitative from a small, selected sample; counts are not population estimates. Current UK authorization, Canadian DIN, Australian scheduling and a TA1-specific anti-doping ruling remain unverified.

Related to Thymosin alpha-1

VIP: A blood-vessel and immune signal studied in lung disease; nasal CIRS benefits remain unproven.
BPC-157: An experimental repair peptide with mostly animal evidence and a few small human reports.
TB-500: A short piece of thymosin beta-4 with no proven repair benefit in humans.
GHK-Cu: A copper-binding skin peptide with small topical studies and untested systemic injections.
MOTS-c: A peptide the body makes; injection benefits and safety remain unproven.
Epitalon: A peptide with telomerase effects in cells, but no proof that people live longer.

Thymosin alpha-1: the short version

Sources

21 CFR 216.23 — Bulk drug substances that can be used to compound drug products in accordance with section 503A of the Federal Food, Drug, and Cosmetic Act., Office of the Federal Register · eCFR · 2026
503B Bulk Drug Substances List, FDA · FDA · 2026
Bulk Drug Substances Nominated for Use in Compounding Under Section 503A of the Federal Food, Drug, and Cosmetic Act, FDA · FDA · 2026
Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks, FDA · FDA · 2026
MHRA Products | Home, MHRA · MHRA · 2026
TGA strengthens compliance focus on unapproved peptide products as part of evolving risk response, Therapeutic Goods Administration · TGA · 2026
The 2026 Prohibited List, World Anti-Doping Agency · WADA · 2026
The Prohibited List, World Anti-Doping Agency · World Anti-Doping Agency · 2026
Think twice before injecting peptides bought online: unauthorized products can seriously harm you, Health Canada · Health Canada · 2026
Thymosin Alpha 1 [Zadaxin], Singapore National Drug Formulary · 2026
Bulk Drug Substances Nominated for Use in Compounding Under Section 503B of the Federal Food, Drug, and Cosmetic Act, FDA · FDA · 2025
December 4, 2024 Pharmacy Compounding Advisory Committee (PCAC) Meeting, FDA · 2024
December 4, 2024 Pharmacy Compounding Advisory Committee Meeting, FDA · 2024
Fraudulent Coronavirus Disease 2019 (COVID-19) Products, FDA · 2020
Public summary of positive opinion for orphan designation of thymalfasin for the treatment of hepatocellular carcinoma, European Medicines Agency

Sources checked: 2026-10-18.

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