subcutaneous

Thymulin

Thymulin (Facteur Thymique Sérique / FTS / Nonathymulin)

Thymulin at a glance

Not on either FDA list

How studies gave it

Injected into the fat under the skin

Evidence on this page

3 peer-reviewed papers, published 1977 to 2014

FDA compounding lists

It appears on neither of the two FDA compounding tables.

What it is

A naturally occurring zinc-dependent nonapeptide (pyroGlu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn) produced by thymic epithelial cells. Originally characterized by Jean-François Bach and Mireille Dardenne at INSERM, Paris, in 1977. Thymulin requires equimolar zinc binding for biological activity — the zinc-free form (FTS) is inactive. It has been studied in animal models for T-cell differentiation, NK cell enhancement, anti-inflammatory effects, and neuroendocrine signaling.

Limited human clinical data exists from two double-blind, placebo-controlled trials in rheumatoid arthritis. Circulating thymulin levels decline with age, correlating with thymic involution. Not approved as a drug in any major market.

Published research

Bach and Dardenne published the foundational characterization of thymulin in Nature in 1977. Two randomized, double-blind, placebo-controlled trials in rheumatoid arthritis (Amor et al., 1987) tested three dose levels, with 5 mg/day showing 56% significant clinical improvement vs. 17% for placebo (p<0.02). Preclinical research has demonstrated T-cell differentiation induction, NK cell enhancement, cytokine modulation (reduction of TNF-α, IL-1β, IL-6 in inflammatory models), and bidirectional thymus-pituitary neuroendocrine communication.

Development by Santen Pharmaceutical for RA and ischemic heart disease was discontinued. More recently, gene therapy approaches using metFTS analogs and the synthetic analog PAT (Peptide Analog of Thymulin) have been explored in preclinical models.

What the terms on this page mean6 terms

animal model: A test in animals standing in for the human condition. Results often fail to carry over to people.
double-blind: Neither the participants nor the researchers know who received the real substance.
placebo-controlled: Part of the group receives an inactive substitute for comparison.
preclinical: Laboratory and animal work done before any testing in people.
analog: A molecule built to copy a natural one with a deliberate change, usually to make it last longer or bind more tightly.
peptide: A short chain of amino acids, the building blocks of proteins.

Compounding status

Not on either FDA list

FDA listing: Thymulin appears on neither FDA's category 2 table nor its table of withdrawn nominations.
What that means: Absence from both lists is not permission to compound. Section 503A allows a bulk drug substance only where a USP or NF monograph exists, or the substance is a component of an FDA-approved drug product, or it appears on the 503A bulks list.

Source: Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks, FDA. Content current as of 2026-04-22; read 2026-09-05. This describes what a compounding pharmacy may supply. It is not advice about your own use.

Reading up on Thymulin is the easy part

Keeping the schedule straight is the hard part. PepKit is the app for that.

Does the reconstitution math for you
Logs each dose and reminds you when the next is due
Counts down every vial's expiration

Where this came from3 references

Each one was resolved at PubMed and confirmed to be the work this page cites. Author, title, journal and year come from the PubMed record, not from the page text.

Biochemical characterisation of a serum thymic factor
Bach J, et al.. Nature (1977). PMID 300146.
Nonathymulin in rheumatoid arthritis: two double blind, placebo controlled trials
Amor B, et al.. Annals of the rheumatic diseases (1987). PMID 3310925.
Physiology and therapeutic potential of the thymic peptide thymulin
Reggiani PC, et al.. Current pharmaceutical design (2014). PMID 24588820.

About this page

Reviewed 2026-08-11. This page reports what published studies and FDA documents say. It carries no dose, cycle length or stack, and it does not tell you whether a substance is appropriate for you. Side-effect reports circulating on forums are self-reported rather than measured, so they are not republished here.

See the editorial policy for how corrections are handled.