Geldanamycin is primarily used in research for its potent inhibition of heat shock protein 90 (Hsp90). By binding to Hsp90, it disrupts the proper folding and stabilization of a variety of client proteins, many of which are involved in cell signaling, proliferation, and survival—particularly in cancer cells. This makes it a valuable tool in oncology research, especially in studying tumor growth and protein degradation pathways. Its ability to induce the degradation of oncogenic proteins such as HER2, BCR-ABL, and mutant p53 has led to its evaluation as a potential anticancer agent. However, due to toxicity and stability issues, geldanamycin itself is not used clinically, but it has served as a lead compound for developing more tolerable derivatives like 17-AAG (tanespimycin) and 17-DMAG, which have entered clinical trials. In addition to cancer research, geldanamycin is used to study cellular stress responses, protein homeostasis, and chaperone function. It is also employed in virology to investigate viral replication processes that depend on Hsp90, showing potential in antiviral studies.