Immune & ThymicMaturing human RCT base

Zadaxin / Thymalfasin

Thymosin Alpha-1, 28-aa thymic peptide

A 28-amino acid thymic peptide that modulates innate and adaptive immunity via TLR signaling, one of the most clinically tested peptides in existence.

Immune Anti inflammatory

Amino acids

35+

Countries approved

>11,000

Trial subjects

Mechanism of action

How Thymosin Alpha-1 works

A thymic peptide that tunes the immune system, strengthening antiviral T cell responses while also calming overactivity. The most clinically tested peptide in this library.

Thymosin α1

28-aa thymic peptide

TLR2 / TLR9

Dendritic cells

T cell balance

Th1 + Treg

Immune modulation

Antiviral and tolerance

Also studied

Strengthens Th1 antiviral T cell responses via TLR2/TLR9 on dendritic cells, the basis for its hepatitis B and immune adjunct use.

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Also drives IDO mediated regulatory T cell tolerance, which is why it's studied in both immune deficient and overactive states.

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Approved in 35+ countries for chronic hepatitis B/C; backed by 30+ trials and post marketing surveillance of over 600,000 patients.

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Applications

Research applications

Chronic hepatitis B

Antiviral immune adjunct

Controlled human trial

Approved in 35+ countries

Immune reconstitution

Adjunct therapy

Controlled human trial

30+ trials, >11,000 subjects

Sepsis

Immune modulation

Controlled human trial

Mixed; TESTS trial

Bars indicate how far the evidence has progressed (in vitro to animal to human), not the size of any effect.

Compound data

Molecular profile

CAS number62304-98-7

Molecular formulaC129H215N33O55

Molecular weight3108.3 g/mol

Type28-aa thymic peptide (N-acetylated)

SequenceAc-Ser-Asp-Ala-Ala-Val-Asp-Thr-Ser-Ser-Glu-Ile-Thr-Thr-Lys-Asp-Leu-Lys-Glu-Lys-Lys-Glu-Val-Val-Glu-Glu-Ala-Glu-Asn

AppearanceWhite lyophilized powder

Literature

Key studies

Aliment Pharmacol Ther2001

The efficacy of thymosin in the treatment of chronic hepatitis B virus infection: a meta-analysis

Chan HL, Tang JL, Tam W, Sung JJ

Key finding

Pooled across 5 RCTs (353 patients), thymosin roughly doubled the sustained virological response vs control (OR 2.67) at 12 months post treatment.

View on PubMed

Full profile

Evidence, safety & status

Claimed benefits & evidence

One of the most clinically tested peptides in existence, >30 trials, >11,000 subjects, post marketing surveillance of >600,000 patients; approved in 35+ countries for chronic hepatitis B/C and as an immune adjunct. Hepatitis B data is strongest. Sepsis data is mixed (the large 2025 TESTS trial is the strongest controlled evidence). Anti aging/general immune support use has no RCT.

Safety & dangers

Among the cleanest safety profiles of any peptide, a 2024 review found it safe and well tolerated across all indications, with no significant treatment related adverse events at therapeutic doses.

Contraindications

Caution in immunosuppression for organ transplant (immune activation) and in autoimmune disease.

Regulatory status

Never FDA approved despite global use. Category 2 (Sept 2023); nomination withdrawn Sept 2024; PCAC voted against 503A inclusion (Dec 2024) despite arguably the strongest human evidence on the list. WADA: S0/related.

Administration

Subcutaneous; standard 1.6 mg twice weekly.

Source: Fnx Performance Peptide Research Database, a synthesis of the scientific and regulatory literature, not medical advice. Anyone considering these compounds should consult a qualified physician.

For research use only

For Research Use Only. Not for human or animal consumption. Products are sold strictly for in vitro laboratory research, not for compounding or therapeutic application.