MZP-54

This compound has the unique properties of selectively degrading BRD3 and BRD4 at low nanomolar concentration, while not affecting BRD2. It thereby shows a distinct profile from other BET bromodomain PROTACs that are either degrading all BET family members or are more BRD4 specific. This compound therefore may have specific applications in targeting BRD3 and BRD4 concomitantly. However, caution should be used as cellular specificity has not been profiled in an unbiased format. While effects on cell proliferation and MYC repression confirm on target activity, no data confirming selectivity beyond the BET family have been reported using e.g. global proteome profiling. 

While there are better degraders for BRD4, it offers an orthogonal probe to the JQ1 derived degraders that the authors had previously disclosed.  It also demonstrates slightly different selectively BRD4/3 vs BRD4.