These include drugs that target sirtuins, and drugs that inhibit the mechanistic target of rapamycin (mTOR) networks, whose signalling is increasingly understood to influence longevity and ageing. mTOR inhibition has been shown to increase lifespan in animal models and reduce respiratory changes in older humans.^20212223 Two such drugs under investigation are the immunosuppressant rapamycin,²⁴ and metformin, a drug originally prescribed for Type 2 diabetes and other metabolic diseases, which had the “side effect” of reducing the incidence of other diseases of age compared to the purportedly healthy, non-diabetic controls against whom they were compared.²⁵

Trials of metformin and rapamycin²⁶ suggest that these small molecule drugs can change the biology of ageing in tissues to a younger profile. Another approach is senolytics, which target senescent cells before they can damage tissues. Gene therapy and stem cells are other possible approaches to rejuvenating old organs.