Alignment and overlay of this crystal structure with the X-ray structure of (R)-OXFBD04 (3) bound to BRD4(1) WT (PDB ID: 6FSY) revealed a high overall structural similarity (Figure ). While there is some small variation in the ZA loop where the mutation is located (backbone alignment variation of 0.41 Å RMSD for the full protein), OXFBD04 (3) retains the key interactions with N140 and Y97 of BRD4(1) L94C (Figure and). In the previously reported X-ray crystal structure, of (R)-OXFBD04 (3) bound to BRD4(1) WT (PDB ID: 6FSY), electron density for only one enantiomer was