Thymosin-α1 vs Thymogen

Two approved-abroad immune peptides, very different scale

Both support immune function, both are approved outside the US, and both are nearly unknown within it. Thymosin-α1 is a 28-amino-acid peptide with trials in hepatitis B and C, sepsis and cancer, approved in more than thirty countries. Thymogen is a two-amino-acid dipeptide, about as small as a biologically active peptide gets, registered in Russia and used for immune recovery during infection and after surgery. The thymosin evidence base is substantially larger and more international; the Thymogen literature is almost entirely Russian.

A close view of a few human lymphocytes with gently textured cell membranes, one partially cut away to reveal a large nucleus. Neutral immune cell anatomy.

Thymosin-α1 Immune Thymalfasin, Zadaxin, Tα1 Full entry →

A medical illustration of the human thymus in the upper anterior chest, two soft lobes behind a faint translucent sternum, with subdued nearby anatomical landmarks for orientation.

Thymogen Thymus & immune system Thymagen, Oglufanide, EW dipeptide Full entry →

Thymosin-α1 compared with Thymogen
	Thymosin-α1	Thymogen
Evidence behind it	Human trials	Human trials
Worth knowing	Approved abroad but never FDA-approved; evidence quality varies by indication.	The most clinically used of this family, but the trials are Russian and mostly older.
Approval	Approved · 30+ countries	Approved · Russia
Category	Immune	Thymus & immune system
What it is	A 28-amino-acid peptide naturally made in the thymus. It helps T cells mature and strengthens the response of immune cells to viruses and tumors. It has been studied in hepatitis B and C, sepsis, cancer and as a vaccine booster.	A two-amino-acid peptide first isolated from calf thymus extract and now made synthetically. It is the most clinically used of this family, given to support immune recovery during infections and after surgery or radiation.
How it works	Naturally produced by the thymus. Drives T-cell maturation and restores immune responsiveness that declines with age.	A Khavinson short peptide: at two to four amino acids it is small enough to pass through cell and nuclear membranes intact. The proposed mechanism is that it binds specific sites on nuclear DNA and changes which genes are switched on in its target tissue, rather than acting on a surface receptor the way most peptides do.
What studies report	Improved response rates in chronic hepatitis B and C, often alongside other therapy Improved survival signals in sepsis trials, including a large Chinese COVID-era study Used as a vaccine adjuvant in older adults	Used clinically in Russia to support immune recovery during infection and after surgery or radiation Studied in hepatitis B and C
Dosing	From studies 1.6 mg twice weekly, subcutaneous — Chronic hepatitis B and C trials. Improved response rates, often alongside other therapy Reported, not evidence 1.6 mg twice weekly mirrors the trial schedule Used in longer courses during illness season	No published dose, and no community figure we would repeat
Why people take it	Immunosenescence (age-related immune decline)Chronic hepatitis B and CAcute viral infectionAdjuvant in oncologyImmune support during infectionChronic hepatitis	Immune recovery during infectionPost-surgical recoveryHepatitis support
In practice	Used in longer courses during illness season or alongside infection Prescribed in countries where it is approved; obtained otherwise elsewhere Appears in pre-mixed vials with BPC-157 and thymosin-β4	Nothing recorded
Route	Subcutaneous injection, from reconstituted lyophilised powder	Subcutaneous injection, or oral capsule depending on the preparation

Rows describing reported use say what people do, not what has been shown to work. Evidence strength is graded the same way across the whole library, so the two columns are directly comparable.

Read the full entries

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