Figure 2. Optimal dose of rapamycin for maximal net benefits. Life extension by rapamycin is dose-dependent in rodents. The higher the dose, the higher the anti-aging benefits, including cancer prevention and life extension. In humans, side effects are dose-dependent and net benefits could potentially decrease at very high doses. This point of the highest net benefit is the optimal dose. The optimal dose varies in different individuals due to the variability of potential side effects. Thus, the optimal dose in a particular individual is determined by the emergence of side effects. The treatment can be viewed as life-long phase I/II clinical trial.