HSP90 is a member of the family of heat shock proteins responsible for folding proteins into
mature conformations and thus maintaining their biological function in cells. Since it is involved in
all hallmarks of cancer, HSP90 has been considered as a promising drug target for cancer therapy.
Eighteen HSP90 inhibitors have entered clinical trials, however, none has been approved by the FDA.
There is still a great need for novel HSP90 inhibitors with strong anticancer activity and good safety
profile. In the past several years, many new molecules were identified as HSP90 inhibitors and some
of them have shown promising pharmacological profiles in preclinical evaluations. In this review,
HSP90 inhibitors identified from 2014 to date are summarized and their design strategies, chemical
structures, and biological activities are reviewed. The inhibitors are categorized by their different target
domains and selectivity as N-terminal, C-terminal, and isoform-selective HSP90 inhibitors.