Gossamer Bio, Inc. announced that the U.S. Food and Drug Administration (the “FDA”) has placed a partial clinical hold on all trials of GB5121, in response to serious adverse events that have been observed in the Phase 1b/2 STAR-CNS study, including atrial fibrillation, a sudden death event and a fatal intracranial hemorrhage. The Company previously announced that it had paused enrollment of the Phase 1b/2 STAR-CNS Study based on the benefit /risk profile observed to date and a prioritization of resources to support the Company's seralutinib program. Based on the foregoing factors, the Company has decided to terminate all ongoing studies and discontinue development of GB5121.