4.3.1 Effect of rapamycin on immunity
The encouraging anti-aging effects of rapamycin in animal studies have spurred a great interest in translating these results to human. Intriguingly, rapamycin at a high dose is known to suppress the immune system, which is why it has been used as an immunosuppressant in organ transplantation. However, when tweaking rapamycin to a lower dosage, rapamycin appears to stimulate immunity. In 2014, a milestone study on the immunity-boosting effect of rapamycin was reported by researchers at Novartis 154. In a double-blind randomized study, they administered everolimus, a derivative of rapamycin, to 218 healthy subjects aged 65 and older for 6 weeks and then stopped the use for 2 weeks before giving them a flu shot. A twenty percent increase of immune response was observed in the everolimus-receiving group, indicating that rapamycin and its analogs (rapalogs) may boost immunity in humans. Furthermore, to minimize the adverse effects of rapamycin, a combination of rapamycin and rapalogs have been subsequently explored. A low dose of rapalogs combined with catalysts have been shown to induce a 40% infection reduction in the healthy elderly (aged 65 and older) subjects who received the rapamycin treatment before flu shot —and more importantly, this combination of therapy was suggested to be well-tolerated in the majority of the subjects 155.