Iodine I 124 Icapamespib

**Semantic type:** Pharmacologic Substance

**Definition:** A radioconjugate composed of icapamespib, a synthetic purine-scaffold inhibitor of the molecular chaperone heat shock protein 90 (Hsp90), conjugated to the radioisotope iodine I 124, with potential imaging activity upon positron emission tomography (PET). Upon administration of iodine I 124 icapamespib, the icapamespib moiety selectively binds to cancer cells expressing stress-induced Hsp90 (stress Hsp90). Upon PET, Hsp90-overexpressing cancer cells can be visualized and patients who may benefit from icapamespib therapy can be identified. This radioconjugate may also be used to determine the pharmacokinetics of icapamespib. Icapamespib is able to cross the blood-brain-barrier (BBB) and specifically targets stress Hsp90, as seen in certain conditions, such as cancer and neurodegenerative diseases, while normal housekeeping Hsp90 complexes are not targeted by icapamespib at dose levels administered for imaging. Additionally, housekeeping Hsp90 complexes are only targeted at doses that are much larger than that are needed to exert an anticancer effect.

**Synonyms:** - 124I-PU-AD - ICAPAMESPIB I-124 - Iodine I 124 PU-AD - [124I]-PU-AD