BRD4-D2 BRD2-D2 Our published compound, 1, yielded results consistent with our previous publication, confirming its behavior as a BRD4-D1 selective inhibitor. Our new analog, 2, also displayed a similar initial selectivity but was approximately 2-fold weaker at inhibiting BRD4-D1 compared to 1 (IC50 = 111 versus 59 nM, respectively). Our AlphaScreen platform also gave consistent results for 3, showing low nanomolar affinity for both BRD4 bromodomains, and an approximately10-fold selectivity for BRD4-D1 and -D2 over BRD2-D2. Taken together, these data provide us with a suite of control compounds that we can employ to analyze differential selectivity. While ZL0454 and ZL0590 have been previously used in inflammation-driven airway remodeling, given the uncertainty in binding and selectivity, we chose to focus on 1 and 2 as BRD4-selective probes along with pan-D1 biased inhibitor, 3.