Protocol
Thymosin alpha-1 and thymosin beta-4 (TB-500)
thymosin · Thymosin Alpha-1 · Ta1 · Thymalfasin · Zadaxin · Thymosin Beta-4 · Tbeta4 · TB-500
The two peptides sit at very different points on the evidence curve, and neither has longevity evidence. Thymosin alpha-1 has a real clinical trial record, but in infectious disease and oncology adjunct settings, not healthspan. The most decisive recent datapoint is negative: the TESTS trial (BMJ, 2025), a multicentre double-blind placebo-controlled phase 3 study in 1,106 adults with sepsis, found 28-day all-cause mortality of 23.4% on thymosin alpha-1 versus 24.1% on placebo (HR 0.99, 95% CI 0.77-1.27, P=0.93) and did not meet its primary endpoint. Earlier meta-analyses in sepsis and COVID-19 suggested a possible mortality benefit, but those were built on smaller, mostly single-country trials and are outweighed by the adequately powered phase 3 result. Thymosin beta-4 is weaker still: its human data come from RegeneRx's phase 2 programme in dermal wound healing and dry eye disease (topical/ophthalmic RGN-259), and no completed phase 2 or phase 3 RCT has tested systemic injectable thymosin beta-4 or TB-500 for tendon, ligament or muscle injury, which is the use most buyers are actually seeking. Regeneration and anti-ageing claims for TB-500 rest on rodent and in-vitro work plus mechanism. Two further caveats: TB-500 is a fragment and is not pharmacologically interchangeable with the full-length thymosin beta-4 used in the trials, and compounded peptide supplied outside the ARTG carries no assurance of identity, purity or dose. Thymosin beta-4 is also banned in sport at all times by WADA under the growth factors category, which matters for any athletic client.
At a glance
- Evidence
- Preclinical
- Singapore (HSA)
- Split status, and different from the Australian picture. Thymosin alpha-1 IS registered with HSA: Zadaxin Injection is a live HSA-registered product (licence SIN07483P, subcutaneous), indicated as monotherapy or in combination with interferon for chronic hepatitis B. It is not subsidised and it is not registered for any immune-ageing, healthspan or longevity indication, so any longevity use would be off-label prescribing of a registered medicine. Thymosin beta-4 / TB-500 could not be verified as an HSA-registered product in this session and appears not to be registered; it is therefore treated as an unregistered therapeutic product, which in Singapore may only reach a patient through a doctor under HSA's unregistered-product import/supply provisions. No Singapore clinic from the supplied universe was verified as offering either peptide.
- Australia (TGA)
- Not on the ARTG. Neither peptide is TGA-approved or registered for any indication in Australia. Thymosin beta-4 and TB-500 are explicitly named in Schedule 4 and in Appendix D of the Poisons Standard, confirmed on the NSW Health Schedule 4 Appendix D list of prescribed restricted substances, which are prescription-only substances judged liable to abuse, misuse and diversion and subject to more stringent possession and supply controls. Possession without a lawful prescription or professional authority is an offence. Where supplied lawfully, they are prescriber-directed compounded preparations from a licensed Australian compounding pharmacy, or accessed via the TGA Special Access Scheme or Authorised Prescriber pathway. The specific scheduling entry for thymosin alpha-1 could not be verified from an authoritative TGA source and is left unstated rather than guessed; it is in any case not ARTG-registered. Australian clinics were verified offering these peptides (GL Vitality Drips lists both for consultation and prescription; Folium Health in Sydney references TB-500), but neither clinic appears in the supplied variis universe.
- Offered at
- No clinic on file
Singapore
Health Sciences Authority
- HSA status
- Split status, and different from the Australian picture. Thymosin alpha-1 IS registered with HSA: Zadaxin Injection is a live HSA-registered product (licence SIN07483P, subcutaneous), indicated as monotherapy or in combination with interferon for chronic hepatitis B. It is not subsidised and it is not registered for any immune-ageing, healthspan or longevity indication, so any longevity use would be off-label prescribing of a registered medicine. Thymosin beta-4 / TB-500 could not be verified as an HSA-registered product in this session and appears not to be registered; it is therefore treated as an unregistered therapeutic product, which in Singapore may only reach a patient through a doctor under HSA's unregistered-product import/supply provisions. No Singapore clinic from the supplied universe was verified as offering either peptide.
- In our SG set
- Tracked in Singapore
- SG clinics
- None on file
Australia
Therapeutic Goods Administration
- TGA status
- Not on the ARTG. Neither peptide is TGA-approved or registered for any indication in Australia. Thymosin beta-4 and TB-500 are explicitly named in Schedule 4 and in Appendix D of the Poisons Standard, confirmed on the NSW Health Schedule 4 Appendix D list of prescribed restricted substances, which are prescription-only substances judged liable to abuse, misuse and diversion and subject to more stringent possession and supply controls. Possession without a lawful prescription or professional authority is an offence. Where supplied lawfully, they are prescriber-directed compounded preparations from a licensed Australian compounding pharmacy, or accessed via the TGA Special Access Scheme or Authorised Prescriber pathway. The specific scheduling entry for thymosin alpha-1 could not be verified from an authoritative TGA source and is left unstated rather than guessed; it is in any case not ARTG-registered. Australian clinics were verified offering these peptides (GL Vitality Drips lists both for consultation and prescription; Folium Health in Sydney references TB-500), but neither clinic appears in the supplied variis universe.
- In our AU set
- Tracked in Australia
- AU clinics
- None on file
Evidence is not approvalAn evidence grade describes how strong the science is. A regulatory status describes whether a body has approved the intervention for an indication. They are different questions, answered separately above.
What it is
Plain-language explainer
Two unrelated thymic peptides usually marketed together by peptide clinics. Thymosin alpha-1 (thymalfasin) is a 28-amino-acid immunomodulating peptide that augments T-cell function and is a licensed medicine in a number of Asian and European markets for chronic hepatitis B. Thymosin beta-4 is a 43-amino-acid actin-binding protein involved in cell migration and wound repair; TB-500 is a shorter synthetic fragment (residues 17-23) sold as a stand-in for it. In longevity practice they are promoted for immune resilience, tissue repair, injury recovery and inflammation, none of which is an approved indication for either peptide in Singapore or Australia.
Categories
Protocol
Keep reading
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Sources
What this profile is built on
- Thymosin Alpha 1 [Zadaxin] - active ingredient record, one HSA-registered product (Zadaxin Injection, SIN07483P) · Singapore National Drug Formulary (MOH)
- ZADAXIN INJECTION [SIN07483P] product information · Singapore National Drug Formulary (MOH)
- Schedule 4 Appendix D drugs - prescribed restricted substances (lists 'TB-500' and 'Thymosin beta 4 (thymosin B4)') · NSW Health, Pharmaceutical Services
- The efficacy and safety of thymosin alpha-1 for sepsis (TESTS): multicentre, double blinded, randomised, placebo controlled, phase 3 trial - primary endpoint not met · BMJ, 2025 (via PubMed)
- Efficacy of thymosin alpha-1 for sepsis: a systematic review and meta-analysis of randomized controlled trials · Frontiers in Cellular and Infection Microbiology, 2025
- The Poisons Standard (the SUSMP) · Therapeutic Goods Administration
- Thymosin Beta-4 peptide hormone information - banned in sport at all times · Sport Integrity Australia
- Peptides available for consultation and prescription, listing Thymosin Alpha-1 and Thymosin Beta-4; notes non-ARTG substances require individual prescription and compounding · GL Vitality Drips (AU)
- Peptide therapy Sydney - references TB-500 alongside BPC-157 · Folium Health (Sydney)
Every entity profile on variis is sourced. Not medical advice.