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Updated: Jun 21, 2026
Malachite Green Assay for the Discovery of Heat-Shock Protein 90 Inhibitors
Published on: January 20, 2023
Retaspimycin hydrochloride (IPI-504): a novel heat shock protein inhibitor as an anticancer agent
Britt Erika Hanson1, David H Vesole
1Loyola University Chicago, Stritch School of Medicine, Division of Hematology/Oncology, Department of Medicine, 2160 S 1st Avenue Maywood, IL 60153, USA.
Abstract:
Heat shock proteins are vital to cell survival under conditions of stress. They bind client proteins to assist in protein stabilization, translocation of polypeptides across cell membranes and recovery of proteins from aggregates. Heat shock protein inhibitors are a diverse group of novel agents that have been demonstrated to have pro-apoptotic effects on malignant cells through inhibition of ATP binding on the ATP/ADP-binding pocket of the heat shock protein. Initial development of heat shock protein 90 inhibitors, geldanamycin and 17-AAG, were limited by hepatotoxicity and the need for solvent carrying agents. In contrast, retaspimycin, or IPI-504, a derivative of geldanamycin and 17-AAG, is highly soluble in water and generally well tolerated. In Phase I/II trials, retaspimycin has shown activity in NSCLC and gastrointestinal stromal tumor. The most promising activity was observed in gastrointestinal stromal tumors. Phase I/II trials are currently underway to evaluate the dosing schedules and activity of IPI-504 in breast cancer. Given the in vitro activity in diffuse large B-cell lymphoma, mantle cell lymphoma, melanoma, leukemia and pancreatic cancer, current and future trials are of clinical interest. This article reviews IPI-504 and its utility in a wide variety of cancer phenotypes.
Insights
Heat shock protein inhibitors like retaspimycin (IPI-504) show promise in cancer treatment by targeting heat shock protein 90. This drug is well-tolerated and effective in early trials for various cancers.
Area of Science:
- Oncology
- Molecular Biology
- Pharmacology
Background:
- Heat shock proteins (HSPs) are crucial for cellular survival and protein homeostasis under stress.
- HSP inhibitors, particularly those targeting HSP90, exhibit anti-cancer properties by inducing apoptosis in malignant cells.
- Early HSP90 inhibitors like geldanamycin had limitations including toxicity and poor solubility.
Purpose of the Study:
- To review the novel heat shock protein inhibitor, retaspimycin (IPI-504).
- To discuss the therapeutic potential and clinical utility of IPI-504 across various cancer types.
Main Methods:
- Review of preclinical and clinical data on retaspimycin (IPI-504).
- Analysis of Phase I/II trial results for IPI-504 in different cancer indications.
- Evaluation of in vitro activity data for IPI-504 in various hematologic and solid tumors.
Main Results:
- Retaspimycin (IPI-504) is a water-soluble, well-tolerated HSP90 inhibitor.
- Promising activity observed in Phase I/II trials for non-small cell lung cancer (NSCLC) and gastrointestinal stromal tumors (GIST).
- Significant activity noted in GIST, with ongoing trials in breast cancer and potential interest in lymphoma, melanoma, leukemia, and pancreatic cancer.
Conclusions:
- Retaspimycin (IPI-504) represents an improved therapeutic option compared to earlier HSP90 inhibitors.
- IPI-504 demonstrates clinical activity in several cancer types, warranting further investigation.
- Ongoing and future clinical trials are essential to fully establish the role of IPI-504 in cancer therapy.
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