Pimitespib: First Approval.

Pimitespib (Jeselhy®) is an oral small molecule inhibitor of the α and β isoforms of heat shock protein 90 (HSP90). HSP90α and HSP90β regulate the stability and activity of a number of proteins that are crucial for tumour development. Pimitespib is being developed by Taiho Pharmaceutical for the treatment of solid tumours, including gastrointestinal stromal tumour (GIST), and in June 2022 it received its first approval in Japan for GIST that has progressed after chemotherapy. Pimitespib is undergoing phase I development for the treatment of solid tumours in the EU and the USA. This article summarizes the milestones in the development of pimitespib leading to this first approval for GIST that has progressed after chemotherapy.