RTB101 dosage and evidence
Written by Aaron CuhaReviewed Sep 2026
The short answer
The most important failed trial in ageing research. It looked good in two mid-stage trials, then did nothing in a 1,024 person final-stage trial. The lab marker it targeted still moved in both of the later trials.
Evidence grade for RTB101: Moderate. The rule: at least one finished study in people, and at least 100 people who took it. The sum on this page: 1 completed trial, 1,024 people given it. A grade counts how much has been done to people, not whether it works.
- People given it
- 1,024
- Human studies
- 1
- Found nothing
- 0
Dose
No human dose established
Amounts that were given in studies sit in Human evidence on this page. None of them is a personal dose.
1 completed trial, 1,024 people given it
3 effects reported, 2 unwanted, 1 wanted, by people using it, not a trial
In plain English
In plain English, from Aaron
This is how I would explain it to a friend. The evidence, with the numbers, is further down the page.
RTB101 is a low dose pill that blocks part of a growth switch called mTOR. It was tested to help older adults fight off chest and airway infections. It looked good at first, then failed its big trial. It was never approved.
What people take it for
- Fewer chest and airway infections in older age.
- Slowing immune ageing, the same idea behind rapamycin.
What studies in people showed
The final-stage trial had 1,024 older adults. 26 percent caught a chest or airway illness on the drug. 25 percent did on a dummy pill. No difference. Earlier, smaller trials had looked good. The odd part is that the drug did exactly what it was built to do inside the body. It switched on antiviral genes in both of the later trials. It just did not keep anyone healthier. It was safe and easy to take.
What people report
Reports, not study results
The good
- It was safe and easy to take in the trials.
The bad
- In the big trial, it did not cut chest or airway illness at all.
- It was never approved and is not available.
Where these come from: From the trials on this page. It was never sold, so there are no user reports.
My bottom line
My opinion: read this before you trust any lab marker. The drug hit its target and nobody got healthier. Judge anything you take by how you feel and function, not by one number moving.
An opinion, not a finding. I am a coach, not a doctor.
What it has been measured to do
Nothing indexed yet
The 3 citations on this page do not report a result for any of the 36 goals indexed here. Most of what sits here is something else: a listing of a planned study, a study of how the body handles the drug, a safety report or a government record. None of those tests whether it works.
Show full evidence
What is RTB101?
The most important failed trial in ageing research. It looked good in two mid-stage trials, then did nothing in a 1,024 person final-stage trial. The lab marker it targeted still moved in both of the later trials.
If you read one page on this site about why a moving lab marker is not a result, make it this one.
RTB101 was the drug that carried the mTOR longevity idea into a final test in people. That test was a final-stage trial in 1,024 older adults. It found that 26 percent caught a chest or airway illness with symptoms on the drug, against 25 percent on a dummy pill. No difference. Everything before it had looked good. In 2014, a trial found mTOR blocking improved the response to a flu vaccine. In 2018, a follow up across several centres reported better immune function and fewer infections. Then a mid-stage trial cut chest and airway illness with symptoms.
The detail that makes this a lesson and not just a letdown is this. In both the mid-stage trial and the failed final-stage trial, the drug switched on the antiviral genes it was built to switch on. It did exactly what it was designed to do inside the body, in the trial where it gave no benefit.
That is the whole argument against trusting a mechanism.
How does RTB101 work?
It blocks TORC1 at a low dose. At the higher doses first developed for cancer, dactolisib blocks two things, an enzyme called PI3K and mTOR. The ageing programme used much lower doses meant to block only TORC1. The thinking was that the immune benefits of blocking mTOR show up at doses well below those that weaken the immune system. The goal was to switch on genes triggered by interferon, the body's antiviral alarm, so older adults would be readier to fight viruses. The trials confirmed that effect.
What have studies in people found about RTB101?
An unusually complete human programme. There were two good early trials, a good mid-stage trial, and a large final-stage trial that found nothing. Very few ideas in ageing research have been tested this thoroughly.
- Final-stage trial: 1,024 older adults. 26 percent got sick on the drug against 25 percent on the dummy. No effect.
- Mid-stage trial: it cut chest and airway illness with symptoms, by more than chance would explain.
- The drug hit its target in both trials. The antiviral genes switched on by interferon went up on the drug.
- Safe and well tolerated throughout. Only one patient, in the dummy group, had serious side effects judged to be drug related.
- Three deaths in the mid-stage trial and one in the final-stage trial. None was judged to be caused by treatment.
- The authors themselves say the measures and the choice of patients may need work before anyone knows if boosting interferon genes really cuts viral infections in older adults.
What this does not tell you: The failure is specific. It is about this drug, this dose, this measure and these people. It does not prove that blocking mTOR has no ageing benefit. Rapamycin's lifespan record in mice is untouched. What it does prove is that hitting the target, plus two good earlier trials, is not enough to predict a large trial result. Note too that six authors worked for the maker and held shares in it. Looking back, that is a reason to weigh the earlier good trials more carefully.
The state of the research
Read the human mTOR programme as one story, not three papers. The biggest trial came last, and it found nothing. In 2021, a final-stage trial in 1,024 older adults found that 26 percent caught a chest or airway illness with symptoms on the drug, against 25 percent on a dummy pill. The smaller trials before it had all looked good. In 2014, a trial found that everolimus improved older adults' response to a flu vaccine. That was the first believable sign in people that blocking this pathway could improve something that declines with age. In 2018, a follow up reported better immune function and fewer infections. A mid-stage trial, published with the big one in 2021, cut chest and airway illness. And in both of the 2021 trials, the antiviral genes the drug was built to switch on did switch on. The drug did what it was designed to do inside the body, and the benefit vanished. That is the best argument on this site for not trusting a moving lab marker.
The reason this belongs on a longevity site, and not only in an immune system journal, is simple. Almost every compound sold for ageing is sold on a mechanism or a moving lab marker. This programme had more than that. It had a believable pathway, mouse lifespan data behind the pathway, proof in people that the drug hit its target, and two good earlier trials that compared it with a dummy. It still failed when tested at full size. And it still hit its target in the trial where it failed.
That is the bar anything on this site should be measured against. Nothing sold as a supplement comes close to clearing it.
The evidence, in charts
Fig. 1a · how many people
1,024people, across 1 study in people cited here
| Study | People | Share |
|---|---|---|
| Lancet Healthy Longevity 2021 | 1,024 | 100% |
The whole total is one study of 1,024. Counts are the number of people each study on this page says it signed up. That includes studies that only watched people and gave nobody the compound. 2 more studies in people give no headcount and are not counted here. Studies still signing people up are left out, and only studies cited on this page are counted.
Fig. 1b · evidence mix
All 3 sources here are studies in people.
- Study in people · done in people3100%
Counted from the list of sources on this page. It counts only what we cite, so there may be more studies out there. A review counts once, however many studies it sums up.
Fig. 2 · evidence over time
The studies cover 3 different years, 2014 to 2021, counted from the list of sources on this page.
Fig. 3 · legal status at a glance
US
Not approved
UK
Not approved
AU
Not approved
CA
Not approved
Not approved in any of the four countries shown. This is what the law says, not a verdict on the science. See Legal status below for the full text and any notes.
Fig. 4 · how much does what
Nobody has tested different amounts in people
This chart would show how the effect changes as the amount goes up. For this compound, nobody has measured that in people. So we leave it empty. We will not borrow an animal chart and pretend it works the same in people.
Fig. 5 · what the molecule is
- Kind of compound
- Small molecule
- Molecule weight
- 469.5 Da for dactolisib. A small molecule, not a peptide.
- Half-life
- Stated in words, not a numbersee the exact wording below
- Chain length
- None on file
Half-life as stated on file: Not asserted. No reliable half-life figure at the low geroscience doses was resolved in the sources loaded.
No amino acid sequence is on file for RTB101, which is expected: a small molecule is not built from amino acids.
The studies we cite
- Study in people2021Targeting the biology of ageing with mTOR inhibitors to improve immune function in older adults: phase 2b and phase 3 randomised trials
The big trial failed, and it was big enough for that to mean something. Just over a thousand older adults took RTB101 or a dummy every day. About a quarter of each group came down with a chest or airway illness. The earlier, smaller trial had shown a benefit and this one did not repeat it. The drug did switch on antiviral genes as intended, in both trials. It was safe and easy to take. Six authors worked for the company and held shares in it.
Phase 2b reduced clinically symptomatic respiratory illness, odds ratio confidence interval 0.391 to 0.922, p = 0.02. Phase 3 enrolled 1,024 patients, 513 to RTB101 10 mg daily and 510 to placebo, and found 134 of 511 (26%) against 125 of 510 (25%) with clinically symptomatic respiratory illness, odds ratio 1.07 (90% CI 0.80 to 1.42), p = 0.65. Significantly more interferon-induced antiviral genes were upregulated on drug than placebo in both trials. Safe and well tolerated. Funded by resTORbio and the National Institute on Aging. Six authors were employees of, and held equity in, resTORbio, which manufactured the drug.
- Study in people2018TORC1 inhibition enhances immune function and reduces infections in the elderly
This is the earlier, smaller trial that made the case for going bigger. Older adults on a low dose combination reported fewer infections over the following year and mounted a better immune response. It was positive, and it was run across several centres. The much larger trial that followed did not repeat it. An encouraging mid sized result is a reason to keep testing, not a reason to believe.
The positive multicentre phase 2a that justified advancing to phase 2b and 3.
- Study in people2014mTOR inhibition improves immune function in the elderly
This is where the programme started. Older adults given a low dose of an mTOR blocking drug responded better to a flu vaccine than those given a dummy. A vaccine response is a blood measure, not a measure of whether anyone stayed well. The idea was followed through to a large trial in over a thousand people, which found no benefit. Read this as the opening claim, not the conclusion.
The original positive result on influenza vaccine response that started the programme.
Common questions
Has RTB101 been tested in people?
Yes. 1,024 people given it across 1 completed trial cited here, 0 of which found nothing. The most important failed trial in ageing research. It looked good in two mid-stage trials, then did nothing in a 1,024 person final-stage trial. The lab marker it targeted still moved in both of the later trials.
What is the RTB101 dosage?
No human dose established. Amounts that were given in studies sit in Human evidence on this page. None of them is a personal dose. 1 completed trial, 1,024 people given it
Is RTB101 FDA-approved?
Never approved. The final-stage studies missed their main goal, and work on it for this use stopped.
What happened to RTB101?
It looked good in an early mid-stage trial and again in a later one. Then it did nothing in a 1,024 person final-stage trial. 26 percent of the drug group and 25 percent of the dummy group got a chest or airway illness with symptoms. Work on it for that use did not continue.
Does that mean mTOR inhibition does not work for ageing?
Not quite. It means this drug at this dose did not cut chest and airway illness in older adults. Rapamycin's lifespan record in mice stands, and it is the most reliable drug result for lifespan there is. What the failure removes is the claim that the immune benefit in people is proven.
Why does the biomarker detail matter so much?
Because the drug did switch on the antiviral genes it was built to switch on, in the trial where it gave no health benefit. It hit its target, and the result was flat. Any claim built on a lab marker moving should be read against that.
Can I get it?
No. It was never approved and is not available.