Currently 17-AAG and 17-DMAG are not under clinical development but there are many other Hsp90 inhibitors (retaspimycin HCL, NVP-AUY922, NVP-BEP800, CNF2024/BIIB021, SNX-5422, STA-9090 etc.)with better pharmacological and toxicological properties that are currently under investigation, holding great promise in breast cancer treatment [67,68,69,70,71,72,73]. This evidence concerns the gene HSP90AB1 and breast cancer.