Immune Support

Thymosin Alpha-1

Zadaxin · Thymalfasin · Tα1

One of the most human-tested peptides in this entire library — genuinely different territory from most of what's here. It's a real approved drug in over 35 countries, just not the UK or US, prescribed mainly for chronic hepatitis B and as a support alongside cancer treatment. The evidence is strongest for that specific use; a large 2025 trial testing it for sepsis found no clear benefit, a useful reminder that strong evidence for one condition doesn't automatically carry over to every other use it gets marketed for.

28-amino-acid thymic (thymalfasin) that activates TLR2/TLR9 signalling on dendritic cells to drive T-cell maturation and Th1-polarised immune responses, approved internationally as Zadaxin.

How well studied

Tier Guide: A = Well studied, B = Some good studies, C = Early evidence & D = Barely studied

AHow well studiedWell studied

Backed by large human trials — we have solid data on how it works and what it does.

Heightened caution: this compound carries unresolved regulatory, safety or supply-chain concerns in the UK. Nothing here is a recommendation to use it.

How it works

Trains your immune system's "threat recognition" cells to work better and helps immature immune cells mature into the type that fights infection — it adjusts the immune response rather than just switching it up to maximum.

Activates toll-like 2 and 9 on dendritic and myeloid antigen-presenting cells, driving T-cell differentiation, increasing T-cell diversity, and shifting immune responses toward a Th1-polarised profile.

Reported benefits

Real, approved treatment for chronic hepatitis B in dozens of countries, with sustained response in a meaningful share of patients
Used as a support alongside cancer treatment and in immune-suppressed states in countries where it is approved

Who it's typically used for

Chronic viral infection, immune support during cancer treatment, immune decline — genuinely evidenced for specific conditions, not a general wellness claim

Timeline to results

Clinical courses typically run 3-6 months for meaningful immune effect in hepatitis B treatment — not a fast-acting compound

Dosage

Trial protocol — studied under clinical supervision, not a self-dose

1.6mg subcutaneous, twice weekly — the established international clinical protocol used in hepatitis B trials and real-world Zadaxin prescribing in 35+ countries. Not an MHRA-approved dose in the UK.

Side effects

Elevated liver enzymes in those with existing liver diseasereported, linked to the immune response working against hepatic viral infection rather than direct toxicity, but needs monitoring
Immune overactivation risk in those with autoimmune conditionsreported

Getting it in the UK

Getting it in the UKPrescribable, but not approved for this

Still legal for a doctor to prescribe, but it hasn't been officially approved for this specific use. Uncommon, and comes down to a specialist's own judgement.

MHRA: the UK government body that checks a medicine is safe and actually works before doctors are allowed to prescribe it.

Content freshness

Last reviewed: 15 Aug 2026
Regulatory status last checked: 15 Aug 2026