Sirolimus (also known as Rapamycin) and Everolimus inactivate the serine/threonine protein kinase mechanistic target of rapamycin (mTOR), a key enzyme for the progression of cellular cycle (from G1 to S phase), thereby inhibiting cell growth and differentiation, in particular of peripheral T cells, but sparing regulatory T cells (Tregs), as shown in Immune-dysregulation, Polyendocrinopathy, Enteropathy, X-linked (IPEX) patients (52), thereby proving beneficial in the clinical setting of immune dysregulation. This evidence concerns the gene MTOR and immune dysregulation-polyendocrinopathy-enteropathy-X-linked syndrome.