A combinatorial screening protocol for identifying novel and highly potent dual-target inhibitor of BRD4 and STAT3 for kidney cancer therapy

Concurrent inhibition of bromodomain-containing protein 4 (<i>BRD4) and</i> signal transductor and activator of transcription 3 (STAT3) could potentially be an effective strategy against renal cell carcinoma (RCC). Here, we successfully identified five dual-targeted BRD4/STAT3 inhibitors (BSTs 1-5) using a combinatorial screening protocol. Particularly, BST-4 was the most potent inhibitor simultaneously targeting BRD4 (IC₅₀ = 2.45 ± 0.11 nM) and STAT3 (IC₅₀ = 8.07 ± 0.51 nM). MD simulation indicated that BST-4 stably bound to the active sites of BRD4 and STAT3. The cytotoxicity assays exhibited that BST-4 had a significant antiproliferative activity against RCC cell lines, especially CAKI-2 cells (IC₅₀ = 0.76 ± 0.05 μM). Moreover, <i>in vivo</i> experiments revealed that BST-4 more effectively inhibited the growth of xenograft tumors compared with positive controls RVX-208 and CJ-1383. Overall, these data indicated that BST-4 could be a promising candidate compound for RCC therapy.