Biochem/physiol Actions

FX1 is a BCL6 inhibitor that effectively blocks BCL6 N-terminal BTB domain-mediated corepressors chromosome recruitment (by 61-87%/SMRT and 67-82%/BCOR; 50 μM FX1 for 30 min) and selectively suppresses BCL6-depenent growth (GI50 16-54 μM; >125 μM against BCL6-independent cells) in diffuse large B cell lymphoma (DLBCL) cultures, exhibiting greater affinity than its structure analog 79-6 or BCL6 corepressor SMRT for BTB domain (KD = 7 μM/FX1, 30 μM/SMRT, 129 μM/79-6). FX1 shows greater efficacy than 79-6 in reversing BCL6/corepressors-mediated target genes repression in vitro (IC50 = 35 μM vs. 318 μM with 79-6 by HEK293T-based reporter assay) and in suppressing OCI-Ly7 DLBCL xenograft tumor growth mice in vivo (100% vs. 45% suppression with respective compound via 25 mg/kg/day i.p.).