Head to head
Rapamycin against RTB101
An mTOR inhibitor used off-label against the mTOR-pathway drug that was properly tested and failed. RTB101 was positive in phase 2a and 2b and produced nothing in a 1,024 person phase 3, while the biomarker it targeted still moved in both.
Column A
RapamycinRapamycin (Sirolimus, mTOR inhibitor)
An FDA-approved mTOR inhibitor that extends lifespan in animals and is widely studied off-label at low, intermittent doses for longevity.
Column B
RTB101RTB101 (dactolisib, BEZ235), low-dose TORC1 inhibitor
The most important failed trial in geroscience. Positive in phase 2a and 2b, then nothing in a 1,024-person phase 3, while the biomarker it targeted still moved in both.
Side by side, on the facts we can check
| Attribute | Rapamycin | RTB101 |
|---|---|---|
| Category | Longevity | Longevity |
| FDA status | FDA-approved (Rapamune); longevity use is off-label and investigational | Never approved. The phase 3 programme did not meet its endpoint and development for this indication did not continue. |
| Half-life | ~60 hours | Not asserted. No reliable half-life figure at the low geroscience doses was resolved in the sources loaded. |
| Molecular weight | 914.2 Da | 469.5 Da for dactolisib. A small molecule, not a peptide. |
| Mechanism | Inhibits the mTOR pathway, mimicking aspects of caloric restriction and enhancing autophagy and cellular maintenance. | A low-dose inhibitor of TORC1. At the higher doses originally developed for oncology, dactolisib is a dual inhibitor of phosphoinositide 3-kinase and mTOR. The geroscience programme used substantially lower doses intended to inhibit TORC1 selectively, on the reasoning that the immune benefits of mTOR inhibition appear at doses well below those causing immunosuppression. Its intended downstream effect was upregulation of interferon-stimulated genes, increasing antiviral readiness in older adults, and that effect was confirmed in the trials. |
| Human studies cited | 2 | 3 |
| Legal status, US | FDA-approved (for its labeled use), prescription only | Not approved; research use only |
Frequently asked questions
What is the difference between Rapamycin and RTB101?
Rapamycin: An FDA-approved mTOR inhibitor that extends lifespan in animals and is widely studied off-label at low, intermittent doses for longevity. RTB101: The most important failed trial in geroscience. Positive in phase 2a and 2b, then nothing in a 1,024-person phase 3, while the biomarker it targeted still moved in both.
Which has stronger research evidence, Rapamycin or RTB101?
This database does not grade compounds. It counts what was run in people: 2 of the 3 studies cited on the Rapamycin profile were human work, against 3 of 3 for RTB101. Those counts are of our own citation lists and understate any larger literature, and neither is a recommendation.
Are Rapamycin and RTB101 FDA-approved?
Rapamycin: FDA-approved (Rapamune); longevity use is off-label and investigational. RTB101: Never approved. The phase 3 programme did not meet its endpoint and development for this indication did not continue..
Related posts
Blog articles that cover Rapamycin or RTB101, newest first.
- Longevity / Sep 8, 2026 / 12 minPeptides for Longevity: What the Evidence Actually Shows in 2026
- Longevity / Sep 8, 2026 / 9 minSenolytics in 2026: Dasatinib plus Quercetin, Fisetin, and What Human Trials Have Shown
- Longevity / Sep 8, 2026 / 9 minThe Rapamycin Dosing Debate: What PEARL Tested, the Bioavailability Problem, and What Is Unproven
Reviewed Sep 2026. This page sets two published records side by side. It is educational, it is not medical advice, and it contains no dosing protocols or recommendations for personal use.