GHK Cu Revival Clinic GHK Cu Purepep FOXO4 DRI alleviates age related testosterone secretion insufficiency by targeting senescent Leydig cells in aged mice Aging Peptide inhibitors targeting FOXO4 p53 interactions and inducing senescent cancer cell specific apoptosis bioRxiv The FOXO4 peptide in a DRI conformation (D amino acids in a retro reversed sequence), henceforth named FOXO4 DRI, competes with FOXO4 for p53 binding in a dose dependent manner and doing so with higher affinity.