Extracts and peptides from the thymus, the gland where T cells mature, are marketed to support or 'boost' immunity. The studies in this hub are a Cochrane review in cancer patients, a 1999 narrative review and two animal experiments. This page is about thymus-derived products, not oral marine peptides, for which our search found no human immune trials (see the oral marine peptides page).
A Cochrane review pooled 20 randomised trials of purified thymus extracts. It found no benefit for survival or tumour response, but fewer severe infections during chemotherapy or radiotherapy, a result the authors call preliminary. Most trials had at least a moderate risk of bias.
The same review found a trend toward longer survival with synthetic thymic peptides such as thymosin alpha-1 (risk ratio 1.21; 95% CI 0.94 to 1.56), but it did not reach statistical significance and rests on few trials.
In rats, low-dose Thymalin slowed or reversed a transplanted tumour. In mice, a long-acting engineered form of thymosin alpha-1 (joined to an antibody fragment) slowed two tumour models and raised T-cell numbers. Neither was tested in people, and the second is a different molecule from thymosin alpha-1.
The hub holds no trial of thymic products outside cancer care yet, so it says nothing about these uses. That is a gap in our coverage, not a finding that no trial exists.
How to read the meters
Not yet assessed here
No human trials found
Mostly animal evidence
Limited human evidence
Mixed human results
Consistent in human trials (with caveats)
The dashed fifth segment is always empty: it is reserved for large, independent, replicated human trials that agree, and we have not rated anything that high. “Mixed” and “Limited” share a step because they differ in kind, not in depth. Safety ratings are shown as words only, because a meter beside “limited safety data” could be misread as “safe”.
Verdicts reflect only the studies summarised on this site, last reviewed November 9, 2026. See how verdicts are set.
| Study | Design | Peptide |
|---|---|---|
| Zhukova et al., 2018 | Animal study | Thymalin |
| Wang et al., 2018 | Animal study | Thymosin alpha-1 |
| Wolf et al., 2011 | Meta-analysis | Thymic peptides, Thymosin alpha-1 |
| Cordero et al., 1999 | Review | Thymic peptides |
Zhukova et al., 2018 · Bull Exp Biol Med · Outbred male albino rats with transplanted sarcoma 45; number of animals not given in the abstract
In rats with a transplanted tumour, low-dose Thymalin stopped tumour growth and caused regression in more than half of the animals, and suppressed growth by 78% in the rest. Thymus tissue showed more lymphocyte proliferation and more tissue basophils and…
Wang et al., 2018 · Sci Rep · Mice, including mouse breast cancer (4T1) and melanoma (B16F10) tumour models; numbers not given in the abstract
The authors made a longer-lasting form of thymosin alpha-1 by attaching an antibody fragment. In mice its serum half-life was 25 hours, about 13 times that of thymosin alpha-1. They report it restored lymphocyte counts after immune injury and slowed tumour…
Wolf et al., 2011 · Cochrane Database Syst Rev · 26 randomised trials; 2,736 adults with cancer receiving chemotherapy, radiotherapy or both
Purified thymus extracts (20 trials) did not improve overall survival (risk ratio 1.00; 95% CI 0.79 to 1.25), disease-free survival (0.97; 0.82 to 1.16) or tumour response (1.07; 0.92 to 1.25). For thymosin alpha-1 the pooled survival ratio was 1.21 (95% CI…
Cordero et al., 1999 · Arch Immunol Ther Exp (Warsz) · Literature on thymic peptides and thymus preparations up to 1999
A 1999 overview of thymic peptides and preparations. Its abstract says only that the possible human uses were still being worked out, and that the paper covers the peptides' general characteristics and recent advances.
Educational information only. It is not medical or legal advice, and nothing here is a recommendation to use any peptide. Talk to a clinician before starting a supplement or treatment.