Most of what this dossier holds about thymus restoration comes from patent abstracts, which assert effects without showing data. The TRIIM study is a different kind of document: a small human trial, published in Aging Cell in 2019 by Gregory M. Fahy, Robert T. Brooke, Steve Horvath and colleagues, that imaged the thymus before and during treatment and reported numbers. That makes it useful twice over. It shows what measured evidence of thymic regeneration looks like, and its design shows clearly where such evidence still falls short.
What was tested, and why
TRIIM stands for Thymus Regeneration, Immunorestoration, and Insulin Mitigation. The authors start from Thymic Involution, the age-related replacement of thymic tissue by fat. Citing earlier work, they say this leads to a collapse in T-cell receptor diversity after about age 63. They therefore enrolled men aged 51 to 65, the age range just before that collapse.
The main agent was recombinant human growth hormone (rhGH). The paper cites animal studies and studies in HIV patients as evidence that it promotes thymic growth. Growth hormone tends to raise insulin, so the protocol added DHEA and metformin to counter that effect. The authors note that neither of these two drugs is known to act on the thymus by itself. Doses were adjusted for each volunteer to keep IGF-1 high and insulin low. The trial ran from 2015 to 2017 under an FDA investigational new drug number (IND 125,851) with approval from an institutional review board. As a pre-Phase I exploratory study, it was not preregistered on clinicaltrials.gov.
What was measured
The thymus was imaged with MRI on a single 3T scanner at Stanford. The authors say there was no standard method for measuring thymic fat, so they borrowed a fat-quantification technique previously used on bone marrow. From it they calculated a thymic fat-free fraction (TFFF): the share of the gland that is not fat. A rising TFFF is read as fat being replaced by functional tissue. They applied the same method to the sternal bone marrow (BMFFF). Blood was analysed for immune cell subsets by mass cytometry (CyTOF), and DNA methylation was used to calculate four "epigenetic clocks" (Horvath, Hannum, PhenoAge and GrimAge).
What the paper reports
- Thymus. The paper reports a significant overall rise in TFFF, at p = 8.57 × 10⁻¹⁷ by linear mixed-model analysis. Individually, 7 of 9 volunteers improved significantly. The two who did not had unusually little thymic fat at the start. The authors found that the size of the response depended on baseline fat content, not on age.
- Bone marrow. BMFFF also rose, by less but very consistently. The authors argue that the different pattern in thymus and marrow points to a thymus-specific effect, not just general fat loss from growth hormone.
- Immune cells. Monocytes fell by about 35% and CD38-positive monocytes by about 40%, which raised the lymphocyte-to-monocyte ratio. PD-1-positive CD8 T cells declined. Naive CD4 and CD8 T cells, and CD4 recent thymic emigrants, rose modestly. Markers of senescent T cells did not change consistently.
- Safety markers. PSA indices and C-reactive protein improved, IL-6 was unchanged, and glucose stayed within the normal range. Reported side effects were mild and typical of growth hormone, including joint pain, carpal tunnel syndrome and mild gynecomastia.
- Epigenetic age. Averaged over the four clocks, epigenetic age fell relative to chronological age by about 2.5 years at 12 months. Six months after treatment stopped, more than 1.5 years of that change remained. GrimAge showed a gain of about 2.1 years that had not faded by month 18. The abstract calls this the first report of an increase in predicted human lifespan from an intervention available today.
What the evidence does and does not show
This is real measurement, but in a deliberately small pilot. The authors themselves say the results need replicating in "an appropriately powered follow-up study." Several limits follow from the paper's own methods sections:
- Size. Ten men were recruited and one was withdrawn after about a month, so results come from nine. The 18-month follow-up covers only the first cohort, because the second cohort of three was not available.
- No control group. Every volunteer received treatment, and each was compared only with his own baseline. Without an untreated or placebo group, the trial cannot rule out changes from time, season or behaviour.
- Combined treatment. Three drugs were given together, plus vitamin D3 and zinc supplements. The design cannot show which agent caused which change. The authors even raise the possibility that the epigenetic effects arise independently of the immune changes.
- New endpoints. TFFF was a method adapted for this study. Epigenetic clocks estimate biological age; they do not measure lifespan directly. The lifespan claim is a prediction from GrimAge, not an observed outcome.
- Statistics. P values were not corrected for multiple comparisons. The authors justify this on the grounds that the results were highly correlated.
- Interests. Four authors held shares or options in Intervene Immune, which funded the study. Two of them are named on a related patent application.
- Population. Only healthy men were studied, so the trial says nothing about women.
The authors also acknowledge that many gerontologists prefer lowering growth hormone and IGF-1 signalling, not raising it. They argue that earlier studies supporting that view are confounded by mutations present from development. That disagreement remains open in the paper itself.
How it fits the dossier
Read next to Thymus Therapy Claims vs. Evidence: The Patent-Abstract Dossier Without Clinical Data, TRIIM shows what the patent abstracts in Thymus Therapies: The source archive Patent-Abstract Dossier lack. It imaged the human thymus directly instead of weighing rodent organs, as in the Thymus Index and Spleen Index Assay. It reported effect sizes and p-values, worked under regulatory oversight, and disclosed its conflicts. It still sits low on the evidence ladder. It is an uncontrolled, unreplicated pilot run by investigators with a commercial interest. It supports the idea that the adult Thymus Gland can change measurably. It does not establish that this regimen is safe or effective, and it does not lend support to the unrelated mechanisms claimed in the patents. See also Patent as Evidence.
Reference
- Fahy GM, Brooke RT, Watson JP, et al. "Reversal of epigenetic aging and immunosenescent trends in humans." Aging Cell 2019;18:e13028. doi:10.1111/acel.13028. https://pmc.ncbi.nlm.nih.gov/articles/PMC6826138/
Source notes & attribution
- https://pmc.ncbi.nlm.nih.gov/articles/PMC6826138/