Animal experiment:

Mice[1]For engraftment studies, C57BL/6 WT mice are engrafted with 1E7 cells by tail-vein injection of splenocytes derived from Eμ-TCL1 or Eμ-Myc/TCL1 mice with active disease. At the onset of leukemia (Eμ-TCL1: ≥ 10% CD19/CD5/CD45-positive circulating cells; Eμ-Myc/TCL1: WBC count ≥ 8 and/or ≥ 5% CD19/CD5/CD45-positive circulating cells), mice are randomized to receive treatments as indicated. PLX51107 20 mg/kg, qd (once daily), oral gavage. Vehicle = 10% N-methyl-2-pyrrolidone plus diluent (40% PEG400, 5% TPGS, 5% Poloxamer 407, and 50% water). Mice are sacrificed when meeting early removal criteria (>20% weight loss, impaired motility, splenomegaly, and evident tumor masses), and tissues are collected for further analysis[1].

PLX51107 is a potent and selective BET inhibitor, with Kds of 1.6, 2.1, 1.7, and 5 nM for BD1 and 5.9, 6.2, 6.1, and 120 nM for BD2 of BRD2, BRD3, BRD4, and BRDT, respectively; PLX51107 also interacts with the bromodomains of CBP and EP300 (Kd, in the 100 nM range).

PLX51107 is a potent and selective BET inhibitor, with Kds of 1.6, 2.1, 1.7, and 5 nM for BD1 and 5.9, 6.2, 6.1, and 120 nM for BD2 of BRD2, BRD3, BRD4, and BRDT, respectively. PLX51107 also interacts with the bromodomains of CBP and EP300 (Kd, in the 100 nM range). PLX51107 (0.156-10 uM) suppresses the CpG-induced proliferation of primary chronic lymphocytic leukemia (CLL) cells. PLX51107 also causes accumulation of p21 and IκBα, reduces c-MYC level, and modulates proapoptotic and antiapoptotic proteins. PLX51107 selectively modulates CLL driver genes[1].

PLX51107 (2 mg/kg, p.o.) inhibits splenomegaly by 75% in the Ba/F3 (murine IL3-dependent pro-B-cell line) splenomegaly mouse model, with the similar effect of 25 mg/kg OTX015. PLX51107 (20 mg/kg, qd, p.o.) exhibits potent antileukemic effects in disease models of aggressive chronic lymphocytic leukemia (CLL) and Richter transformation (RT) via oral administration once daily[1].

References:
[1]. Ozer HG, et al. BRD4 Profiling Identifies Critical Chronic Lymphocytic Leukemia Oncogenic Circuits and Reveals Sensitivity to PLX51107, a Novel Structurally Distinct BET Inhibitor. Cancer Discov. 2018 Apr;8(4):458-477.