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What it is
A nonapeptide produced by thymic epithelial cells, biologically active only when bound to zinc — which is why zinc status directly determines its activity, an unusually clean dependency.
How it is proposed to work
Proposed roles in T-cell differentiation and immune regulation. Circulating levels fall with age alongside thymic involution, which is the basis for interest in it as an immune-ageing intervention.
Approved medical uses
None. Thymulin has no approved human medical indication in the jurisdictions we track. Any use is outside an approved label.
Human research
Each entry states what the study found and, separately, what it cannot show.
- Randomised controlled trial1987
Nonathymulin in rheumatoid arthritis: two double blind, placebo controlled trials
Finding. Nonathymulin — described in the report as "a synthetic thymic peptide hormone", and indexed by PubMed under the same substance heading as thymulin — was compared with placebo across three dose schedules in two randomised, double-blind trials in rheumatoid arthritis. Only one of the three, the middle schedule, was reported as working: the abstract names it the most efficient dose and gives no comparable result for the other two. For that schedule, the global assessment of all patients who entered the trials gave 56% improved against 17% on placebo (p less than 0.02), with improvement also on four objective parameters. The authors report minimal adverse effects and no clear changes in immunological parameters, though they add that a significant correlation was observed involving clinical response and T cell subset imbalance, assessed with monoclonal anti-T cell antibodies and a functional suppressor T cell assay.
Limitation. The headline figure is the best of three dose schedules, reported across both trials together rather than trial by trial, and it carries the usual discount for a dose identified as the winner after the comparison. The abstract states no enrolment figure, so the size of either trial cannot be judged from it, and "minimal adverse effects" is not itemised. Its closing sentence on the immunological correlation is garbled as published, so what correlated with what is not clear from the abstract alone and we have not read the full text. This is a single 1987 report; the compound was not carried into a modern development programme, and we could not establish why — commercial abandonment and quiet failure look identical from the outside.
Preclinical research
Animal and laboratory work. Useful for generating hypotheses; it cannot establish that something works in people.
No preclinical studies catalogued.
Potential safety concerns
- CautionInsufficient
No modern human safety dataset. Immunomodulators warrant caution in autoimmune disease.
Known interactions and contraindication considerations
- Relevant to consider alongside immunosuppressive therapy.
This list is not exhaustive and is not a substitute for a clinician reviewing your full medication history.
Regulatory status
Status is shown per jurisdiction and is accurate only as of the date stated. Where a compound is approved, the approval is bound to a specific formulation, manufacturer and indication — shown in the detail column.
| Jurisdiction | Standing | Detail |
|---|---|---|
United States FDA | Unapproved / investigational as of 11 Aug 2026 | No marketing authorisation. The FDA has not evaluated this compound — that is an absence of any opinion, not a negative finding. |
European Union EMA | Unapproved / investigational as of 11 Aug 2026 | No marketing authorisation. |
India CDSCO | Unapproved / investigational as of 11 Aug 2026 | Not approved for human use. A first-time synthetically manufactured peptide falls under the new-drug pathway. |
How it is being used
What the grey community actually runs, the reasoning they give, and our read on whether it follows from known biology. This is observation, not evidence, and not a recommendation.
No community use documented for this compound yet. Absence here means our editorial team has not reviewed and verified a pattern — not that none exists.
Active clinical trials
No registered trials currently tracked for Thymulin.
What remains unknown
The questions that would change our assessment if they were answered.
- Does restoring thymulin affect immune function in ageing humans?
- Is zinc status the more tractable intervention, given the dependency?
References
Editorial change history
When we change a grade or a regulatory note, we log it here rather than editing quietly.
Dossier created. A narrative that it was 'out-competed commercially rather than refuted' was rejected — that is a causal story built from absence of data.
Spotted something wrong? Tell us — we publish corrections.