PU-H71 is a selective inhibitor of heat shock protein 90 (HSP90), particularly targeting the inducible form HSP90α. It is primarily used in cancer research due to its ability to destabilize oncogenic client proteins involved in tumor growth and survival. PU-H71 shows strong affinity for HSP90 complexes in tumor cells, making it a valuable tool for studying HSP90-dependent pathways in malignancies such as breast cancer, leukemia, and lymphoma. It has been utilized in preclinical studies to inhibit tumor progression and induce apoptosis in cancer cells. Its selectivity for tumor-associated HSP90 allows for more precise targeting, reducing effects on normal cells. PU-H71 is also employed in imaging applications, where labeled versions help visualize HSP90 expression in tumors, aiding in diagnosis and treatment monitoring. Due to its role in disrupting protein folding machinery in cancer cells, it is being explored in combination therapies with other anticancer agents to enhance efficacy and overcome drug resistance.