Rapamycin

Rapamycin, also known as Sirolimus, is a powerful macrolide compound originally discovered in the soil of Easter Island (Rapa Nui). While initially classified as an antifungal, it is FDA-approved as a prescription immunosuppressant to prevent organ transplant rejection and to treat a rare lung disease called lymphangioleiomyomatosis (LAM). In the field of geroscience, Rapamycin is considered the most robust pharmacological candidate for extending lifespan and healthspan, having consistently increased the lives of every animal species tested, including yeast, worms, flies, and mice. It is currently the focus of intense research for its potential to delay age-related decline in humans.

Rapamycin works by specifically inhibiting a protein complex called mTORC1 (mechanistic Target of Rapamycin Complex 1). This complex acts as a central 'nutrient sensor' that tells cells when to grow and divide. When nutrients are abundant, mTOR is active; however, chronic mTOR overactivation is a hallmark of aging. By inhibiting mTORC1, Rapamycin shifts the body’s cellular state from growth and protein synthesis to maintenance and repair. A key mechanism triggered by this inhibition is autophagy, a cellular 'self-cleaning' process that breaks down and recycles damaged proteins and organelles. This metabolic shift effectively mimics the beneficial biological effects of caloric restriction.

For its FDA-approved uses (transplant medicine), Rapamycin is taken daily at doses typically ranging from 1–5 mg. However, for longevity and healthspan (currently off-label), researchers emphasize intermittent dosing to minimize side effects. The landmark PEARL trial (2025) and geroscience experts like Dr. Matt Kaeberlein suggest a common experimental protocol of 2 mg to 10 mg taken once weekly. Users should: 1) Consult a physician, as Rapamycin requires a prescription and careful medical supervision. 2) Monitor biomarkers, including fasting glucose, HbA1c, and lipid panels (cholesterol/triglycerides), as Rapamycin can affect metabolism. 3) Avoid grapefruit, which can dangerously increase drug levels in the blood. 4) Pause during infection, as even low doses may slightly alter immune response. It is generally not recommended for children, pregnant women, or those with active infections or impaired wound healing.