Its contribution to the overall regulation of chaperone function is not clear, but some small molecules that interact with the C-terminal domain, such as the antibiotic novobiocin [26] (Nvb, Figure 1) and coumermycin A1 (Cm A1), induce client protein degradation without heat shock response induction [27,28,29,30,31], giving new promise to Hsp90 inhibition for cancer treatments. Here, HSP90AA1 is linked to cancer.