Structural Insights and Comparative Analysis of HSP90: Implications in Design of Inhibitors

Abstract

Heat shock protein 90 (HSP90) is an important molecular chaperone involved in the stabilization and regulation of multiple client proteins that contribute to cancer cell growth, survival, and progression. Its central role in oncogenic signaling has made HSP90 an attractive target for anticancer drug development. However, despite extensive efforts to develop potent HSP90 inhibitors, clinical translation has remained challenging, highlighting the need for a more comprehensive understanding of the structural and mechanistic determinants of HSP90 inhibition. This review provides a structural and mechanistic analysis of HSP90, with particular emphasis on the domain organization, ATP-dependent chaperone cycle, conformational dynamics, and structural differences between HSP90α and HSP90β. The binding characteristics of HSP90 inhibitors are discussed according to their interaction with the N-terminal ATP-binding region, C-terminal region, and alternative or allosteric binding sites, with emphasis on the distinction between conserved interactions and structural features that may support isoform or paralog selectivity. Recent computational approaches, including virtual screening, molecular docking, and molecular dynamics simulations, are critically evaluated in relation to experimental biochemical, cellular, and structural validation. The review further examines the clinical development of selected HSP90 inhibitors and identifies factors contributing to limited clinical translation, including toxicity, adaptive heat-shock responses, pharmacokinetic and pharmacodynamic limitations, and difficulties in achieving adequate selectivity and therapeutic efficacy. Collectively, these findings indicate that high binding affinity within the conserved N-terminal ATP-binding pocket alone may be insufficient for successful therapeutic development. Future HSP90 inhibitor design should therefore integrate structural selectivity, conformational dynamics, adjacent sub pockets, alternative binding sites, target engagement, and appropriate experimental validation to support the development of more selective and clinically useful HSP90-targeted therapies.