XY221 (Compound 16o) selectively inhibits BRD4 BD2 with an IC50 of 5.8 nM. It demonstrates high selectivity for pan-BD2 and BRD4 BD2 domains, being 667 times more selective than for BRD4 BD1, and 9-32 times more selective than for BRD2/3/T BD2. XY221 can induce apoptosis in MV4-11 cells and exhibits anti-cancer activity.

BRD3 BD2:70.98 nM(Ki)

XY221 displays inhibitory activity against several bromodomains with IC50 values of 5.8 nM for BRD4 BD2, 70.98 nM for BRD3 BD2, 53.47 nM for BRD2 BD2, 183 nM for BRDT BD2, and 3869 nM for BRD4 BD1 [1]. It also inhibits the proliferation of MV4−11, LNCaP, and HL-7702 cells with IC50 values of 0.51 μM, 0.68 μM, and 47.7 μM, respectively [1]. Treatment with XY221 at concentrations ranging from 500 to 2000 nM over 72 hours significantly suppresses proliferation and induces apoptosis in MV4-11 cells [1]. In liver mitochondria, both mouse (RLM) and human (HLM), XY221 exhibits a half-life exceeding 120 minutes at 1-10 μM concentration for 2 hours [1]. At 500-2000 nM over 72 hours, XY221 reduces phosphorylation of target genes p21, ODC1, BRD4, and proteins AKT, AMPK in MV4−11 cells [1]. Furthermore, at 2 μM for 72 hours, it lowers the mRNA expression of oncogene MYC and its target gene p21, along with cell cycle-related gene BCL-2 in MV4−11 cells [1].