Thymosin Alpha-1 is not FDA approved. Zadaxin is a real medicine elsewhere.
Thymalfasin has a substantial human research record, but large modern sepsis and pancreatitis trials missed their main outcomes. FDA has not approved a Thymosin Alpha-1 product in the United States and flags compounding risks. Singapore separately registers an exact prescription Zadaxin product. This guide keeps those facts in the right countries and product lanes.
The molecule has human trials and foreign approvals, but neither creates an approved US product.
FDA stated that no product containing Thymosin Alpha-1 is approved in the United States. Its advisory committee voted 4 to 17 against adding both the free base and acetate to the 503A Bulks List. FDA's current safety page also flags immunogenicity, impurity, and API-characterization concerns for compounded products.
Singapore's government formulary separately lists Zadaxin Injection as a registered prescription medicine for defined hepatitis indications. That is a meaningful country-specific product record, not a transferable approval for a US research vial, clinic preparation, online seller, or another destination.
Read the Thymosin Alpha-1 record in four fields.
This is a sourced status snapshot, not a safety score, treatment recommendation, or seller certification. Each field links back to the detailed record below.
Multiple disease-specific trials
Hepatitis, sepsis, pancreatitis, COVID-19, and cancer studies cannot be combined into a universal immune-benefit claim.
Inspect the human evidenceMixed and indication-specific
The largest modern sepsis and pancreatitis trials did not meet their main clinical endpoints.
Audit the popular claimsNo approved US product
FDA says no TA1 product is approved and its 2024 panel voted 4 to 17 against 503A listing for both forms.
Check status and destination routesDated US price boards
Molecule, US status, human outcomes, and foreign medicine records must stay separate.
A useful answer preserves the exact peptide form, finished product, country, indication, comparator, outcome, formulation, manufacturer, and source date.
Thymalfasin is a 28-amino-acid peptide
PubChem records thymalfasin, Thymosin Alpha-1, and Zadaxin as related names for a defined acetylated peptide sequence. That molecule record does not authenticate a seller vial, establish its salt form, or prove purity, sterility, stability, strength, or lawful supply.
No FDA-approved Thymosin Alpha-1 product
FDA stated directly in its December 2024 advisory meeting that products containing Thymosin Alpha-1 are not approved in the United States. Orphan designations, foreign approvals, human studies, and compounding nominations are separate from FDA approval.
Multiple trials, no universal benefit
Thymosin Alpha-1 has been tested in hepatitis, sepsis, acute pancreatitis, COVID-19, cancer, and other settings. Results vary by disease, comparator, era, and outcome. Large modern trials in sepsis and pancreatitis did not meet their main clinical goals.
Zadaxin is a real prescription product in Singapore
Singapore's government formulary lists Zadaxin Injection as a prescription-only registered product with exact indications. That Singapore record does not create FDA approval, authorize a US research vial, or prove the same product is approved or available in another destination.
Popular Thymosin Alpha-1 claims beside the record that limits them.
Biological activity, an old trial, a foreign product label, and a current seller listing answer different questions.
Thymosin Alpha-1 is FDA approved
FDA stated in its December 2024 advisory meeting that products containing Thymosin Alpha-1 are not approved in the United States. The agency separately reviewed free base and acetate for possible 503A list placement.
Foreign registration, an orphan designation, a study phase, an FDA meeting, or a bulk-substance nomination is not FDA approval. An exact approved application and finished-product label would be required.
Zadaxin approval makes every TA1 vial legitimate
Singapore's current formulary identifies one exact 1.6 mg prescription-only Zadaxin Injection product under registration SIN07483P, with a named licence holder and manufacturer.
That record is product-specific and country-specific. It does not authenticate a US 5 mg research vial, a compounded preparation, a different manufacturer, an imported package, or a seller's shipping claim.
TA1 boosts immunity and prevents infection
Laboratory activity and immune biomarkers support an immunomodulatory mechanism, and some small or older studies reported favorable outcomes in selected settings.
A biomarker shift is not a universal patient benefit. The 1,106-person TESTS trial found no reduction in 28-day sepsis mortality, and the 508-person TRACE trial missed its primary pancreatitis outcome.
Thymosin Alpha-1 treats long COVID or COVID-19
Small randomized COVID-19 trials and observational studies have evaluated thymalfasin in selected hospitalized or high-risk populations.
The cited 49-person randomized pilot did not show statistically significant recovery differences. FDA has not approved Thymosin Alpha-1 for COVID-19, and this record does not establish a long-COVID treatment effect.
TA1 is proven for hepatitis B or C everywhere
Older hepatitis trials reported mixed virologic and biochemical findings, and Singapore's Zadaxin product record includes hepatitis B and C indications.
FDA's 2024 review found insufficient evidence for the evaluated US compounding uses and noted outdated comparators and design limitations. One country's product label does not become another country's standard of care.
TA1 is safe because trials reported few side effects
FDA's evidence review says most clinical studies described tolerability and commonly reported local injection-site irritation, redness, or discomfort.
FDA separately flags aggregation, impurities, API characterization, and immunogenicity concerns for compounded products. A trial product's tolerability cannot authenticate a different formulation, concentration, lot, or supplier.
A certificate of analysis proves the vial is clinical-grade Zadaxin
A matched laboratory report may support a limited identity, purity, quantity, or contaminant result for the sample actually tested.
It does not establish the registered Zadaxin product, FDA approval, sterility, endotoxin control, stability, lawful supply, clinical benefit, or sample-to-delivered-vial chain of custody.
The largest trials are more informative than the broad immune story.
Mortality, infected necrosis, viral response, clinical recovery, immune biomarkers, and tumor response are different outcomes. A signal in one cannot prove another.
Phase 3 TESTS sepsis trial
- Identity
- Thymosin Alpha-1 versus placebo with clinical sepsis care
- Design
- Multicenter, double-blind, randomized, placebo-controlled Phase 3 trial
- Participants
- 1,106 adults randomized; 1,089 in modified intention-to-treat analysis
Twenty-eight-day mortality was 23.4% with Thymosin Alpha-1 and 24.1% with placebo, with a hazard ratio of 0.99 and P value of 0.93. No secondary or safety outcome differed significantly. Exploratory subgroup signals do not reverse the negative primary result.
TRACE acute necrotizing pancreatitis trial
- Identity
- Thymosin Alpha-1 versus matching placebo
- Design
- Sixteen-center, double-blind, randomized, placebo-controlled trial
- Participants
- 508 adults randomized
The study found that immune-enhancing Thymosin Alpha-1 did not reduce the incidence of infected pancreatic necrosis versus placebo in the full trial population. Later subgroup analyses are hypothesis-generating and cannot replace the primary result.
Hospitalized COVID-19 pilot trial
- Identity
- Thymalfasin plus standard care versus standard care
- Design
- Prospective, open-label, randomized pilot trial
- Participants
- 49 hospitalized adults in the published analysis
Estimated clinical-recovery rates favored treatment in some oxygen strata, but confidence intervals were wide and neither difference was statistically significant. The small open-label study does not establish COVID-19 or long-COVID effectiveness.
Chronic hepatitis B placebo-controlled trial
- Identity
- Thymosin Alpha-1 versus placebo
- Design
- Multicenter, randomized, double-blind, placebo-controlled trial
- Participants
- 97 adults with HBeAg-positive chronic hepatitis B
The defined complete response occurred in 14% of the treatment group and 4% of placebo at month 12, but the difference did not reach statistical significance. The study predates current antiviral standards and does not prove current comparative benefit.
Chronic hepatitis B duration trial
- Identity
- Two Thymosin Alpha-1 durations versus untreated control
- Design
- Randomized, three-group controlled trial
- Participants
- 98 adults with chronic hepatitis B
Delayed virologic response was higher in one treatment group than untreated control, while the longer treatment comparison was not clearly significant. Untreated control, old testing methods, and historical care limit translation to current treatment choices.
Metastatic melanoma combination trial
- Identity
- Thymosin Alpha-1 in several dacarbazine and interferon combinations
- Design
- Randomized, five-arm multicenter study
- Participants
- 488 adults with metastatic melanoma
Some treatment arms recorded responses, but the overall-survival and progression-free-survival comparisons versus control were not statistically significant. Multi-drug combinations and older melanoma care prevent a stand-alone anticancer claim.
Three current facts answer three different questions.
Approval status, 503A advisory advice, and FDA's compounding safety list should not be collapsed into a single label.
No FDA-approved TA1 product
FDA stated directly that products containing Thymosin Alpha-1 are not approved in the United States. Orphan designation is not marketing approval.
Read the FDA transcript →4 yes, 17 no for both forms
The 2024 committee voted against placing both Thymosin Alpha-1 free base and acetate on the 503A Bulks List. The committee advises FDA, and its vote is not itself a final approval or prohibition.
Open the official meeting minutes →Category 2 compounding concerns
FDA identifies possible immunogenicity and complexities involving peptide impurities and API characterization, with inadequate safety information to fully evaluate compounded products.
Check the current FDA list →Thymosin Alpha-1, Zadaxin, and TB-500 are not interchangeable.
A molecule name, exact registered brand, and different thymosin-family fragment carry different evidence and product records.
Thymosin Alpha-1
A 28-amino-acid immunomodulatory peptide also called thymalfasin. Current US research listings require their own identity, lot, and seller evidence.
Open the US market board →Zadaxin
Singapore lists an exact prescription-only 1.6 mg injection under registration SIN07483P. That registered product is not a generic label for every TA1 vial.
Open the Singapore product record →TB-500
A seller-market name generally used for a seven-amino-acid thymosin beta-4 fragment. Its sequence, claimed uses, human evidence, FDA finding, and anti-doping record are separate.
Open the TB-500 evidence guide →A US seller page is not Singapore's registered Zadaxin product.
These are dated public research-market observations, not medical validation. Price and availability do not establish identity, sterility, approval, seller authority, legal access, or suitability.
03
The board compares public US 5 mg pages under one evidence policy. Each row preserves source date, stock language, document route, shipping claim, and limitations.
Inspect every source row →02
Only explicit current availability language enters the count. A row without a usable stock signal cannot set the available-market low.
Check source freshness →$41.00-60.49
The range excludes shipping, taxes, coupons, checkout-only discounts, and ambiguous stock rows. It is a dated market observation, not a recommendation.
Compare landed cost →Thymosin Alpha-1 status changes with the exact product and country.
US FDA status does not erase an exact Singapore medicine registration, and Singapore registration does not authorize a US research vial or create global approval. Check the finished product, strength, licence holder, prescription route, pharmacy, seller, import path, intended claim, and current regulator record for the destination.
Fourteen Thymosin Alpha-1 questions, answered from the exact record.
This is educational reporting, not medical advice, a prescription, emergency guidance, or a use protocol.
What is Thymosin Alpha-1?
Thymosin Alpha-1 is an N-terminally acetylated 28-amino-acid peptide. Thymalfasin is the synthetic form name, and Zadaxin is a finished-product brand used in some countries. Those names can point to related molecular identity, but they do not make every research vial, compounded preparation, or imported package the same finished product.
What are the proven benefits of Thymosin Alpha-1?
There is human research across chronic viral hepatitis, sepsis, acute pancreatitis, COVID-19, cancer combinations, vaccine response, and other selected clinical settings. Results are mixed and indication-specific. Large modern trials did not show a mortality benefit in sepsis or a primary-outcome benefit in acute necrotizing pancreatitis, so no universal immune or wellness benefit is established.
Does Thymosin Alpha-1 boost the immune system?
Laboratory and clinical records show immunomodulatory activity and changes in some immune markers. That describes biological activity, not a guaranteed improvement in infection risk, symptoms, hospitalization, survival, or overall health. In the largest cited sepsis trial, immune-marker and clinical findings did not translate into lower 28-day mortality.
Is Thymosin Alpha-1 FDA approved?
No Thymosin Alpha-1 product is FDA-approved in the United States. FDA stated this directly at its December 2024 advisory meeting. The committee then voted 4 to 17 against placing both the free base and acetate on the 503A Bulks List. That advisory vote and FDA's category 2 safety listing are separate from approval, but neither creates an approved US product.
Is Zadaxin approved anywhere?
Yes, exact foreign prescription records exist. Singapore's National Drug Formulary currently lists Zadaxin Injection under registration SIN07483P as a prescription-only product with Thymosin Alpha-1 and defined hepatitis indications. That Singapore authorization does not prove approval, availability, reimbursement, or lawful import in the United States or any other country.
What are the side effects of Thymosin Alpha-1?
FDA's literature review says the most commonly reported reactions were local irritation, redness, or discomfort at the injection site, while foreign product information includes additional warnings and contraindications for selected populations. Singapore's Zadaxin record also notes possible transient liver-enzyme flares and contraindications. These records do not define the safety of an unverified seller vial or compounded lot.
Does Thymosin Alpha-1 treat sepsis?
The strongest recent answer is negative for the main outcome studied. In the 1,106-person TESTS Phase 3 trial, 28-day mortality was 23.4% with Thymosin Alpha-1 and 24.1% with placebo, with no statistically significant difference. Exploratory subgroup findings may support more research, but they do not establish a general sepsis treatment benefit.
Does Thymosin Alpha-1 treat hepatitis B or hepatitis C?
Older trials reported mixed virologic and biochemical findings, and Singapore's exact Zadaxin product record includes hepatitis B and hepatitis C indications. FDA's 2024 US compounding review concluded that the evaluated evidence was insufficient and often used outdated comparators. The correct answer therefore depends on the exact country, registered product, current standard of care, and clinical indication.
Does Thymosin Alpha-1 treat COVID-19 or long COVID?
The cited randomized pilot in hospitalized COVID-19 patients was small and did not show statistically significant recovery differences. FDA warned a seller that therapeutic COVID-19 claims for its Thymosin Alpha-1 product made it an unapproved new drug. The cited evidence does not establish a treatment for long COVID, prevention of infection, or benefit in a general outpatient population.
Does Thymosin Alpha-1 fight cancer?
The molecule has been studied as part of multi-drug cancer regimens, but this does not make it a proven stand-alone cancer treatment. In the cited 488-person metastatic melanoma study, overall-survival and progression-free-survival comparisons did not reach statistical significance. Trial combinations, cancer type, stage, and historical standard of care all matter.
Is Thymosin Alpha-1 the same as TB-500?
No. Thymosin Alpha-1, also called thymalfasin, is a 28-amino-acid peptide associated with immune research. Seller-labelled TB-500 generally refers to a seven-amino-acid thymosin beta-4 fragment associated with a different gene family, sequence, evidence record, FDA finding, and anti-doping context. Similar thymosin names do not make them interchangeable.
Is compounded Thymosin Alpha-1 the same as Zadaxin?
No equivalence should be assumed. Zadaxin authorization belongs to an exact finished product, registration, strength, licence holder, manufacturer, label, and supply chain. FDA flags potential aggregation, peptide-related impurities, API-characterization gaps, and immunogenicity concerns for compounded Thymosin Alpha-1. A matching ingredient name does not bridge those product-quality differences.
What is a safe Thymosin Alpha-1 dosage?
This guide does not provide a personal dose, reconstitution, injection, cycling, or combination protocol. Trial regimens and a foreign prescription label belong to defined products, diseases, populations, and monitoring conditions. They should not be converted into instructions for a US research vial, compounded preparation, imported product, or person without clinician and destination-specific review.
Can I buy Thymosin Alpha-1 legally in my country?
Lawful access depends on the exact country, product registration, prescription and pharmacy route, seller authority, import rules, intended claims, and finished-product identity. A seller's shipping promise, US research listing, Singapore Zadaxin registration, or online certificate does not answer every destination. Use the linked country and state records to verify the current local route.
Do not turn a foreign label or disease trial into a self-use protocol.
The cited studies and Singapore product record involve defined products, diseases, populations, comparators, professional care, and monitoring. A research vial, compounded formulation, blend, imported package, or seller instruction can differ in form, strength, impurities, aggregation, sterility, endotoxin control, storage, exposure, and intended use.
FDA approval, 503A eligibility, foreign registration, country access, seller availability, laboratory testing, and individual clinical care are separate records. This page does not provide dosing, reconstitution, injection, cycling, stacking, or titration instructions.