A Selective Small-Molecule STAT5 PROTAC Degrader Capable of Achieving Tumor Regression In Vivo

The signal transducer and activator of transcription 5 (STAT5) is an attractive therapeutic target but successful targeting of STAT5 has proved to be difficult. We report herein the development of AK-2292 as a first, potent and selective small-molecule degrader of both STAT5A and STAT5B isoforms. AK-2292 induces degradation of STAT5A/B proteins with an outstanding selectivity over all other STAT proteins and >6,000 non-STAT proteins, leading to selective inhibition of STAT5 activity in cells. AK-2292 effectively induces STAT5 depletion in normal mouse tissues and human chronic myeloid leukemia (CML) xenograft tissues and achieves tumor regression in two CML xenograft mouse models at well-tolerated dose-schedules. AK-2292 is not only a powerful research tool with which to investigate the biology of STAT5 and therapeutic potential of selective STAT5 protein depletion and inhibition in vitro and in vivo, but also a promising lead compound toward ultimate development of a STAT5-targeted therapy.