Rapamycin Goes Mainstream: UT Health San Antonio Launches Large-Scale Clinical Trial
UT Health San Antonio launches a National Institute on Aging-funded rapamycin trial with 84 older adults—one of the largest longevity-focused clinical studies to date. The shift: from off-label speculation to evidence-based dosing.
A drug once known almost exclusively for preventing organ transplant rejection is now at the center of a National Institute on Aging-funded clinical study at UT Health San Antonio to determine how rapamycin should be used in older adults to promote healthy aging.
This isn’t just another longevity trial. It’s one of the largest rapamycin studies in healthy older adults to date — and it represents a turning point for a drug that has been circulating in biohacker forums and prescribed off-label at longevity clinics for years without rigorous human data.
Why Rapamycin?
Rapamycin inhibits mTOR (mechanistic target of rapamycin), a cellular pathway that regulates growth, metabolism, and aging. When mTOR activity is reduced, cells shift from growth mode to maintenance mode — repairing damage, clearing debris, and improving stress resistance.
The animal data is compelling. Studies show that rapamycin extends lifespan by up to 60% in mice, 24% in flies, and 20% in yeast.1 It’s one of the most reproducible longevity interventions in biology.
But here’s the problem: the human data is sparse. Most clinical trials have focused on rapamycin’s immunosuppressive effects in transplant patients, not its anti-aging potential in healthy individuals. The dosing regimens used for transplant recipients may be too high — or poorly timed — for safe use in generally healthy older adults.
Enter UT Health San Antonio.
What Makes This Trial Different
Led by Dr. Ellen Kraig, Dr. Dean Kellogg Jr., and Dr. Brett Ginsburg from the Sam and Ann Barshop Institute for Longevity and Aging Studies, this study is structured as a multi-phase translational pipeline designed to answer the questions that matter:
Phase 1: Establish a Baseline
The first sub-study examines immune and metabolic markers in younger adults to define what “optimal” function looks like before aging-related changes begin. This creates a reference point for intervention.
Phase 2: Find the Right Dose
The second sub-study will test different rapamycin dosing schedules in older adults to determine the minimum effective dose that brings biological markers back to youthful levels without causing side effects.
“This phase is about precision,” said Dr. Kellogg. “We’re asking how much drug it actually takes to achieve a desired biological effect, not more than that.”
This is critical. Many longevity clinics currently prescribe rapamycin at doses extrapolated from transplant protocols or anecdotal reports. This trial will establish pharmacokinetic data — how the drug is absorbed, distributed, and cleared in aging bodies — to guide evidence-based dosing.
Phase 3: Long-Term Clinical Trial
The largest cohort: 84 older adults (ages 65-90) randomized to receive either:
- Daily rapamycin
- Intermittent dosing
- Placebo
Treatment will last six months, followed by a six-month observation period to assess both acute effects and whether benefits persist after stopping the drug.
Participants must be generally healthy, non-smokers, living independently, and not using diabetes medications. UT Health San Antonio is currently enrolling; interested individuals can email [email protected] or call (210) 450-3333.
The Broader Context: ARPA-H and PROSPR
UT Health San Antonio’s rapamycin trial is part of a larger shift in how the U.S. government approaches aging research. In February 2026, ARPA-H announced $144 million in funding through its PROSPR program to develop biomarkers and therapeutics for healthspan extension.
One of the seven funded teams is UT Health San Antonio itself, which will conduct a phase 3 hybrid trial testing rapamycin alongside an SGLT2 inhibitor and semaglutide — three drugs already prescribed off-label at longevity clinics but without rigorous aging-specific data.
The goal: establish regulatory pathways for testing aging therapeutics and identify surrogate biomarkers that allow trials to measure efficacy in 1-3 years instead of decades.
“This is about understanding aging biology in humans,” said Dr. Kellogg. “Once you understand that, you can start asking smarter clinical questions.”
What Longevity Clinics Are Already Doing
While UT Health San Antonio builds the evidence base, some longevity clinics have been prescribing rapamycin off-label for years. The typical protocol: 1-6 mg once per week, sometimes paired with other interventions like NAD+ therapy or senolytics.
The appeal is understandable. Rapamycin is FDA-approved (for transplant rejection), available via prescription, and backed by decades of animal research. But the human safety and efficacy data in healthy aging is still limited.
A 2024 systematic review in The Lancet Healthy Longevity found that while rapamycin and its derivatives show promise in early-phase human trials, most studies were small, short-term, and focused on disease-specific outcomes rather than aging itself.2
The UT trial is designed to fill that gap.
Separating Science from Hype
Dr. Kellogg is blunt about the current state of rapamycin use outside clinical trials:
“Rapamycin is a powerful drug. Using it without understanding how it behaves in aging bodies is not the same as careful clinical research.”
This is the tension at the heart of longevity medicine. On one hand, longevity clinics offer early access to promising interventions that might take a decade to reach mainstream medicine. On the other hand, without rigorous data, patients are essentially participating in uncontrolled experiments.
The UT trial aims to bridge this gap by establishing:
- Pharmacokinetics: How rapamycin is processed in older adults
- Optimal dosing: What works, what doesn’t, and why
- Safety profile: Side effects, tolerability, and long-term risks
- Biomarker effects: Which biological markers respond to rapamycin and predict long-term outcomes
What’s Next
Results from the UT Health San Antonio trial are expected within 2-3 years. If successful, the study will provide:
- Evidence-based dosing guidelines for clinicians
- Validated biomarkers for future trials
- A regulatory framework for testing other aging therapeutics
In the meantime, rapamycin remains a high-potential, high-uncertainty intervention. For individuals considering rapamycin outside a clinical trial, the key question is: Are you willing to be an early adopter without knowing the optimal dose, frequency, or long-term effects?
For some, the answer is yes. For others, trials like this one represent the smarter path: let the science catch up to the hype, then make an informed decision.
Related:
- ARPA-H Commits $144 Million to the First Clinical Trials Designed to Extend Healthspan
- Evidence vs. Experimentation: The Longevity Clinic Dilemma