585 The investigational HSP90 inhibitor ganetespib displays robust single agent activity in gastric cancer models both as monotherapy and in combination with standard of care therapeutics

minutes after treatment. We identify a chromatin architecture that defines a durable response to BETi, specifically in the context of immunoglobulin heavy chain (IgH) re-arrangements, classifying patient populations suitable for BET treatment. Our results suggest that the molecular response to BETi is highly dynamic and adapts over time, while high-occupancy BRD4 loading is generally a poor predictor of BET transcriptional control.